[{"Name":"Basics of Water","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Molecule Structure Properties","Duration":"9m 53s","ChapterTopicVideoID":27215,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.830","Text":"Hi there. Welcome to basics of water."},{"Start":"00:04.830 ","End":"00:06.540","Text":"We\u0027re going to be talking about molecules,"},{"Start":"00:06.540 ","End":"00:08.625","Text":"structure, and properties of water."},{"Start":"00:08.625 ","End":"00:10.020","Text":"By the end of this section,"},{"Start":"00:10.020 ","End":"00:12.915","Text":"you\u0027ll be able to understand water\u0027s role in life"},{"Start":"00:12.915 ","End":"00:16.200","Text":"and explain the structure and characteristics of water."},{"Start":"00:16.200 ","End":"00:18.690","Text":"Water is the most abundant substance."},{"Start":"00:18.690 ","End":"00:24.480","Text":"It makes up 70 percent or more of the weight of most organisms."},{"Start":"00:24.480 ","End":"00:27.730","Text":"Life on Earth most likely began in water."},{"Start":"00:27.730 ","End":"00:29.865","Text":"If we focus on ourselves as humans,"},{"Start":"00:29.865 ","End":"00:34.215","Text":"water makes up 60-75 percent of the human body weight."},{"Start":"00:34.215 ","End":"00:37.979","Text":"A loss of just 4 percent of total body water leads to dehydration,"},{"Start":"00:37.979 ","End":"00:43.190","Text":"while a loss of 15 percent of total body water, can be fatal."},{"Start":"00:43.190 ","End":"00:47.285","Text":"Likewise, a person can survive a month without food,"},{"Start":"00:47.285 ","End":"00:50.450","Text":"but wouldn\u0027t survive 3 days without water."},{"Start":"00:50.450 ","End":"00:52.850","Text":"Water is a major component in the cell."},{"Start":"00:52.850 ","End":"00:57.650","Text":"A cell is composed of 70- 95 percent water and it is"},{"Start":"00:57.650 ","End":"01:00.230","Text":"crucial since its properties affect"},{"Start":"01:00.230 ","End":"01:03.695","Text":"the structure and function of all other cellular constituents."},{"Start":"01:03.695 ","End":"01:12.965","Text":"Here we have that it is 70-95 percent of the cell composition."},{"Start":"01:12.965 ","End":"01:15.455","Text":"Let\u0027s move and talk about the water molecule."},{"Start":"01:15.455 ","End":"01:18.695","Text":"Water is a simple molecule composed of"},{"Start":"01:18.695 ","End":"01:23.615","Text":"2 small positively charged hydrogen atoms"},{"Start":"01:23.615 ","End":"01:29.134","Text":"and 1 large negatively charged oxygen atom."},{"Start":"01:29.134 ","End":"01:33.575","Text":"You have 2 small positively charged hydrogen atoms"},{"Start":"01:33.575 ","End":"01:38.795","Text":"and 1 large negatively charged oxygen atom."},{"Start":"01:38.795 ","End":"01:42.890","Text":"When the hydrogens bind to the oxygen,"},{"Start":"01:42.890 ","End":"01:46.250","Text":"it creates an asymmetrical molecule with positive charge on"},{"Start":"01:46.250 ","End":"01:49.910","Text":"1 side and negative charge on the other side."},{"Start":"01:49.910 ","End":"01:53.720","Text":"This charge differential is called polarity,"},{"Start":"01:53.720 ","End":"01:57.485","Text":"and this affects how water interacts with other molecules."},{"Start":"01:57.485 ","End":"01:59.030","Text":"As a polar molecule,"},{"Start":"01:59.030 ","End":"02:03.950","Text":"water interacts best with other polar molecules, such as itself."},{"Start":"02:03.950 ","End":"02:08.300","Text":"You have the 2 small positively charged hydrogen atoms"},{"Start":"02:08.300 ","End":"02:11.450","Text":"and you have the 1 large negatively-charged oxygen atom."},{"Start":"02:11.450 ","End":"02:14.270","Text":"If you see here it says 2 negative because it has"},{"Start":"02:14.270 ","End":"02:18.290","Text":"2 electrons that are orbiting and cause this to negative charge."},{"Start":"02:18.290 ","End":"02:21.305","Text":"They interact with each other and cause a bond."},{"Start":"02:21.305 ","End":"02:26.855","Text":"Now the 2 plus and a 2 minus create a neutral charge of molecule,"},{"Start":"02:26.855 ","End":"02:29.910","Text":"yet it still has polarity."},{"Start":"02:29.910 ","End":"02:34.295","Text":"This side with the 2 hydrogen is the positively charged pole,"},{"Start":"02:34.295 ","End":"02:37.640","Text":"while the oxygen side is the negatively charged pole."},{"Start":"02:37.640 ","End":"02:43.320","Text":"As I said, polar molecules interact best with each other."},{"Start":"02:43.320 ","End":"02:45.170","Text":"Being the oxygen is polar,"},{"Start":"02:45.170 ","End":"02:47.280","Text":"it means it can also interact with itself."},{"Start":"02:47.280 ","End":"02:51.080","Text":"If we see the positive polar side of water,"},{"Start":"02:51.080 ","End":"02:58.775","Text":"it can affiliate and bond with the negatively charged pole of the oxygen."},{"Start":"02:58.775 ","End":"03:04.845","Text":"The same here, positive and negative."},{"Start":"03:04.845 ","End":"03:09.910","Text":"We can see these water molecules interacting with themselves."},{"Start":"03:09.910 ","End":"03:12.320","Text":"Now let\u0027s look at the water molecule from a different perspective."},{"Start":"03:12.320 ","End":"03:17.554","Text":"Let\u0027s assess the electron structure of the water molecule."},{"Start":"03:17.554 ","End":"03:22.130","Text":"This reveals the cause of these intermolecular attraction."},{"Start":"03:22.130 ","End":"03:26.224","Text":"Each hydrogen atom of a water molecule shares an electron pair"},{"Start":"03:26.224 ","End":"03:28.580","Text":"with the central oxygen atom."},{"Start":"03:28.580 ","End":"03:31.670","Text":"Now, the shape of the molecule is defined by"},{"Start":"03:31.670 ","End":"03:36.500","Text":"the outer electron orbitals and this refers to the passive and electron"},{"Start":"03:36.500 ","End":"03:39.920","Text":"around the nucleus of an atom because the electrons are constantly in"},{"Start":"03:39.920 ","End":"03:44.855","Text":"motion and they\u0027re orbiting around the nucleus of the atom."},{"Start":"03:44.855 ","End":"03:50.239","Text":"The oxygen has a hydrogen atom at each of 2 corners."},{"Start":"03:50.239 ","End":"03:56.000","Text":"It\u0027s to its sides and unshared electron pairs at the other 2 corners."},{"Start":"03:56.000 ","End":"04:00.140","Text":"These orbitals result in a rough tetrahedron shape."},{"Start":"04:00.140 ","End":"04:05.300","Text":"Now to remind you, we introduced this word tetra from, you guessed it."},{"Start":"04:05.300 ","End":"04:15.250","Text":"Greek language comes from the word Tettares in Greek, which means 4."},{"Start":"04:15.470 ","End":"04:20.615","Text":"It has a shape that has 4 sides."},{"Start":"04:20.615 ","End":"04:23.450","Text":"We\u0027re talking about a nearly tetrahedral arrangement because"},{"Start":"04:23.450 ","End":"04:26.690","Text":"it\u0027s not that there are actually 4 molecules."},{"Start":"04:26.690 ","End":"04:34.415","Text":"But we see 2 of the sides is the electron pairs of the oxygen."},{"Start":"04:34.415 ","End":"04:41.570","Text":"Here we see the dipolar nature of H_2O and a ball and stick model ball stick."},{"Start":"04:41.570 ","End":"04:46.085","Text":"The dash lines represent the non-bonding orbital."},{"Start":"04:46.085 ","End":"04:53.105","Text":"The electrons that are orbiting around get aren\u0027t actually banned."},{"Start":"04:53.105 ","End":"04:56.360","Text":"Now you can see the nearly tetrahedral arrangement of the outer shell"},{"Start":"04:56.360 ","End":"04:59.450","Text":"electron pairs around the oxygen atom,"},{"Start":"04:59.450 ","End":"05:02.990","Text":"the 2 hydrogen atoms have localized partial positive charges,"},{"Start":"05:02.990 ","End":"05:04.870","Text":"as you see here."},{"Start":"05:04.870 ","End":"05:10.255","Text":"This forms 1 and 2 and then"},{"Start":"05:10.255 ","End":"05:16.325","Text":"the oxygen atom has a partial negative charge, 2 of them."},{"Start":"05:16.325 ","End":"05:21.500","Text":"This creates the nearly tetrahedral form because you have"},{"Start":"05:21.500 ","End":"05:27.560","Text":"1 and 2 of the hydrogens and 3 and 4 for the electron pairs that are orbiting."},{"Start":"05:27.560 ","End":"05:30.750","Text":"Now simplifying this point,"},{"Start":"05:31.000 ","End":"05:38.965","Text":"each individual water molecule has both a negative portion and a positive portion."},{"Start":"05:38.965 ","End":"05:44.030","Text":"Each side is attracted to molecules of the opposite charge."},{"Start":"05:44.030 ","End":"05:47.390","Text":"This attraction allows water to form"},{"Start":"05:47.390 ","End":"05:53.795","Text":"relatively strong connections called bonds with other polar molecules around it."},{"Start":"05:53.795 ","End":"05:56.165","Text":"Including, as mentioned before,"},{"Start":"05:56.165 ","End":"05:58.385","Text":"other water molecules, in which case,"},{"Start":"05:58.385 ","End":"06:01.670","Text":"the 1 positive hydrogen in the water molecule will"},{"Start":"06:01.670 ","End":"06:05.465","Text":"bond with a negative oxygen of the adjacent molecule."},{"Start":"06:05.465 ","End":"06:07.189","Text":"This is 1 molecule,"},{"Start":"06:07.189 ","End":"06:09.065","Text":"this is a second water molecule,"},{"Start":"06:09.065 ","End":"06:12.890","Text":"and the positive hydrogen interacts and bonds with"},{"Start":"06:12.890 ","End":"06:17.780","Text":"the negative side of the water molecule."},{"Start":"06:17.780 ","End":"06:21.770","Text":"The hydrogens are attracted to the next oxygen and"},{"Start":"06:21.770 ","End":"06:25.310","Text":"this can go on if you have the positive charge,"},{"Start":"06:25.310 ","End":"06:30.590","Text":"this hydrogen, another oxygen of a water molecule,"},{"Start":"06:30.590 ","End":"06:33.170","Text":"can also interact with this."},{"Start":"06:33.170 ","End":"06:36.260","Text":"If we sum it up liquid water is"},{"Start":"06:36.260 ","End":"06:40.535","Text":"an essential requirement for life on Earth because it functions as a solvent."},{"Start":"06:40.535 ","End":"06:44.360","Text":"It\u0027s extensive capability to dissolve a variety of"},{"Start":"06:44.360 ","End":"06:49.520","Text":"molecules has earned it the designation of universal solvent."},{"Start":"06:49.520 ","End":"06:53.825","Text":"It is this ability that makes water is such an invaluable life-sustaining force."},{"Start":"06:53.825 ","End":"06:56.720","Text":"Now if we talk about a biological level,"},{"Start":"06:56.720 ","End":"06:57.920","Text":"on a biological level,"},{"Start":"06:57.920 ","End":"07:03.365","Text":"it is capable of dissolving substances and enabling key chemical reactions in animal,"},{"Start":"07:03.365 ","End":"07:05.734","Text":"plant, and microbial cells."},{"Start":"07:05.734 ","End":"07:07.760","Text":"For example, water\u0027s role as a solvent helps"},{"Start":"07:07.760 ","End":"07:11.570","Text":"cells transport and use substances like oxygen or nutrients."},{"Start":"07:11.570 ","End":"07:16.445","Text":"Water-based solutions like blood help carry molecules to the necessary a location."},{"Start":"07:16.445 ","End":"07:18.785","Text":"It\u0027s chemical and physical properties,"},{"Start":"07:18.785 ","End":"07:21.380","Text":"including its molecular and ionic structure,"},{"Start":"07:21.380 ","End":"07:24.890","Text":"allow it to dissolve more substances than most other liquids."},{"Start":"07:24.890 ","End":"07:29.150","Text":"This water\u0027s role as a solvent facilitates the transport of molecules like oxygen,"},{"Start":"07:29.150 ","End":"07:32.100","Text":"as mentioned before, for respiration which is needed."},{"Start":"07:32.100 ","End":"07:33.830","Text":"It\u0027s important for other aspects of biology,"},{"Start":"07:33.830 ","End":"07:35.285","Text":"for example, in therapeutics,"},{"Start":"07:35.285 ","End":"07:39.185","Text":"it has a major impact on the ability of drugs to reach their targets in the body."},{"Start":"07:39.185 ","End":"07:46.355","Text":"Again, we\u0027re talking another form of transport in an organism in the body."},{"Start":"07:46.355 ","End":"07:50.270","Text":"Water also has an important structural role in biology."},{"Start":"07:50.270 ","End":"07:56.430","Text":"Let\u0027s explain this. Water fills cells to help maintain, shape and structure."},{"Start":"07:56.430 ","End":"07:58.010","Text":"The water inside many cells,"},{"Start":"07:58.010 ","End":"08:00.335","Text":"including those that make up the human body,"},{"Start":"08:00.335 ","End":"08:03.455","Text":"creates pressure that opposes external forces."},{"Start":"08:03.455 ","End":"08:05.660","Text":"This is similar to putting air in a balloon."},{"Start":"08:05.660 ","End":"08:07.310","Text":"You blow up a balloon with air."},{"Start":"08:07.310 ","End":"08:08.870","Text":"It grows and grows."},{"Start":"08:08.870 ","End":"08:11.540","Text":"But there\u0027s a point that it\u0027s actually"},{"Start":"08:11.540 ","End":"08:14.690","Text":"hard to put air in the balloon because the actual material of"},{"Start":"08:14.690 ","End":"08:17.600","Text":"the balloon is creating a force that is opposing the pressure that"},{"Start":"08:17.600 ","End":"08:20.600","Text":"the air inside the balloon is enforcing on the material."},{"Start":"08:20.600 ","End":"08:25.100","Text":"Even some plants which can maintain their cellular structure with that water,"},{"Start":"08:25.100 ","End":"08:27.035","Text":"still require water to survive."},{"Start":"08:27.035 ","End":"08:31.685","Text":"Water allows everything inside the cell to have the right shape at the molecular level."},{"Start":"08:31.685 ","End":"08:34.790","Text":"Since shape is critical for biochemical processes,"},{"Start":"08:34.790 ","End":"08:38.640","Text":"this is also 1 of water\u0027s most important roles."},{"Start":"08:38.640 ","End":"08:41.551","Text":"Let\u0027s look at this figure to illustrate this point."},{"Start":"08:41.551 ","End":"08:43.115","Text":"Water impacts cell shape."},{"Start":"08:43.115 ","End":"08:46.730","Text":"Water creates pressure inside the cell like the air in"},{"Start":"08:46.730 ","End":"08:51.215","Text":"a balloon that helps them maintain shape and it\u0027s going against,"},{"Start":"08:51.215 ","End":"08:53.840","Text":"for looking at this hydrated cell on the left,"},{"Start":"08:53.840 ","End":"09:01.130","Text":"the water pushes outward on the cell membrane and the cell maintains a round shape,"},{"Start":"09:01.130 ","End":"09:06.245","Text":"while the outer forces that are pressing inside"},{"Start":"09:06.245 ","End":"09:13.535","Text":"are smaller than the forces of the water pressing outwards."},{"Start":"09:13.535 ","End":"09:17.720","Text":"There\u0027s less water pushing outward because they\u0027re less water molecules."},{"Start":"09:17.720 ","End":"09:22.325","Text":"The pressure from the outside is bigger than the inside."},{"Start":"09:22.325 ","End":"09:27.935","Text":"Therefore, you see their cell is wrinkled, it\u0027s shriveled."},{"Start":"09:27.935 ","End":"09:30.920","Text":"You see here how it impacts"},{"Start":"09:30.920 ","End":"09:34.505","Text":"structure and therefore it\u0027s also important for the structure."},{"Start":"09:34.505 ","End":"09:38.000","Text":"Now, after these crucial bonds that we touched upon"},{"Start":"09:38.000 ","End":"09:41.585","Text":"before between the polar molecules and specifically between the water molecules."},{"Start":"09:41.585 ","End":"09:43.985","Text":"We will learn about these in the next section."},{"Start":"09:43.985 ","End":"09:46.789","Text":"At this point, we should understand"},{"Start":"09:46.789 ","End":"09:50.585","Text":"water\u0027s role in life and be able to explain the structure and characteristics of water."},{"Start":"09:50.585 ","End":"09:53.370","Text":"Let\u0027s move on to the exercises."}],"ID":28333},{"Watched":false,"Name":"Exercise 1","Duration":"4m 11s","ChapterTopicVideoID":27214,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.690","Text":"Hi there. We\u0027re within the chapter of Water,"},{"Start":"00:03.690 ","End":"00:07.670","Text":"and we\u0027re covering basics of water in the section of Water Molecule,"},{"Start":"00:07.670 ","End":"00:10.000","Text":"Structure, and Properties."},{"Start":"00:10.000 ","End":"00:13.530","Text":"Part 1, which of the following is true:"},{"Start":"00:13.530 ","End":"00:17.835","Text":"A loss of just 4 percent of total body water is fatal in humans;"},{"Start":"00:17.835 ","End":"00:21.090","Text":"water is a major component in the cell;"},{"Start":"00:21.090 ","End":"00:24.516","Text":"a cell is composed of 50-70 percent water;"},{"Start":"00:24.516 ","End":"00:28.934","Text":"water is the most abundant substance in living systems;"},{"Start":"00:28.934 ","End":"00:31.200","Text":"as a nonpolar molecule,"},{"Start":"00:31.200 ","End":"00:36.450","Text":"water acts as a major solvent and thus is crucial to cell function;"},{"Start":"00:36.450 ","End":"00:38.490","Text":"all of the above."},{"Start":"00:38.490 ","End":"00:41.705","Text":"Let\u0027s talk about it. We mentioned what happens when"},{"Start":"00:41.705 ","End":"00:44.580","Text":"there is a 4 percent loss of total body water,"},{"Start":"00:44.580 ","End":"00:48.215","Text":"but we mentioned that it leads to dehydration."},{"Start":"00:48.215 ","End":"00:52.610","Text":"So 4 percent results in dehydration,"},{"Start":"00:52.610 ","End":"00:59.660","Text":"or 15 percent of water loss can be fatal,"},{"Start":"00:59.660 ","End":"01:01.940","Text":"so A is not true."},{"Start":"01:01.940 ","End":"01:04.595","Text":"Water is a major component in the cell."},{"Start":"01:04.595 ","End":"01:09.440","Text":"A cell is composed of 50-70 percent water."},{"Start":"01:09.440 ","End":"01:12.380","Text":"We talked about water as a major component in the cell,"},{"Start":"01:12.380 ","End":"01:14.840","Text":"as well as water in the human body."},{"Start":"01:14.840 ","End":"01:16.775","Text":"We actually mentioned higher,"},{"Start":"01:16.775 ","End":"01:18.605","Text":"actually starting with 70."},{"Start":"01:18.605 ","End":"01:25.490","Text":"It is actually 70-95 percent of the composition of a cell."},{"Start":"01:25.490 ","End":"01:30.387","Text":"So once again, this one is incorrect."},{"Start":"01:30.387 ","End":"01:35.890","Text":"Let\u0027s go into C. Water is the most abundant substance in living systems."},{"Start":"01:35.890 ","End":"01:38.925","Text":"Considering we talked about, in the human body,"},{"Start":"01:38.925 ","End":"01:42.105","Text":"the water weight is 50-70 percent,"},{"Start":"01:42.105 ","End":"01:46.920","Text":"and within the cell we said it\u0027s 70-95 percent."},{"Start":"01:46.920 ","End":"01:48.260","Text":"That, either way,"},{"Start":"01:48.260 ","End":"01:50.750","Text":"seems like it is on the highest percent,"},{"Start":"01:50.750 ","End":"01:54.740","Text":"and we did say it\u0027s the most abundant substance in living systems."},{"Start":"01:54.740 ","End":"01:56.330","Text":"So this seems true to me,"},{"Start":"01:56.330 ","End":"02:02.405","Text":"but let\u0027s continue and check D. As a nonpolar molecule,"},{"Start":"02:02.405 ","End":"02:06.965","Text":"water acts as a major solvent and thus is crucial to cell function."},{"Start":"02:06.965 ","End":"02:10.730","Text":"So we do know that it acts as a major solvent. This is correct."},{"Start":"02:10.730 ","End":"02:12.770","Text":"We also know that it\u0027s crucial to cell function,"},{"Start":"02:12.770 ","End":"02:17.150","Text":"but water is actually a polar molecule."},{"Start":"02:17.150 ","End":"02:20.135","Text":"Remember, we have 2 positive H\u0027s,"},{"Start":"02:20.135 ","End":"02:28.975","Text":"and this is the positively charged pole connected to an oxygen that has a 2 negative."},{"Start":"02:28.975 ","End":"02:31.700","Text":"It\u0027s a negative charge on this pole."},{"Start":"02:31.700 ","End":"02:35.045","Text":"Therefore, D is also incorrect."},{"Start":"02:35.045 ","End":"02:40.250","Text":"This also says that E is incorrect because we know that these aren\u0027t correct."},{"Start":"02:40.250 ","End":"02:42.710","Text":"Therefore, the answer can\u0027t be all of the above."},{"Start":"02:42.710 ","End":"02:44.807","Text":"That leaves us with C,"},{"Start":"02:44.807 ","End":"02:48.410","Text":"water is the most abundant substance in living systems."},{"Start":"02:48.410 ","End":"02:54.080","Text":"Part 2 will actually be adjust the sentences that are incorrect,"},{"Start":"02:54.080 ","End":"02:57.415","Text":"so that they are true as well. Let\u0027s go."},{"Start":"02:57.415 ","End":"03:01.370","Text":"A, we talked about this and mentioned a loss of"},{"Start":"03:01.370 ","End":"03:05.765","Text":"just 4 percent of the total body water results in dehydration."},{"Start":"03:05.765 ","End":"03:12.040","Text":"Reminder, a loss of 15 percent total body water can be fatal."},{"Start":"03:12.040 ","End":"03:15.460","Text":"But 4 percent results in dehydration. Let\u0027s go into B."},{"Start":"03:15.460 ","End":"03:17.420","Text":"Water is a major component in a cell."},{"Start":"03:17.420 ","End":"03:19.640","Text":"A cell is composed of 50-70 percent water."},{"Start":"03:19.640 ","End":"03:21.410","Text":"We said this is incorrect."},{"Start":"03:21.410 ","End":"03:25.790","Text":"Therefore, the correct percentage is 70-95 percent water."},{"Start":"03:25.790 ","End":"03:31.085","Text":"Water is a major component in the cell and it is composed of 70-95 percent water."},{"Start":"03:31.085 ","End":"03:32.450","Text":"We said C is true,"},{"Start":"03:32.450 ","End":"03:34.130","Text":"so we don\u0027t need to correct anything here."},{"Start":"03:34.130 ","End":"03:36.230","Text":"Let\u0027s go on to D. We mentioned,"},{"Start":"03:36.230 ","End":"03:39.405","Text":"this sentence, we said this is correct, and this is correct."},{"Start":"03:39.405 ","End":"03:42.260","Text":"Water acts as a major solvent and thus is crucial to cell function."},{"Start":"03:42.260 ","End":"03:45.965","Text":"But we said water is not non-polar."},{"Start":"03:45.965 ","End":"03:48.200","Text":"Water is actually a polar molecule, therefore,"},{"Start":"03:48.200 ","End":"03:53.375","Text":"as a polar molecule water acts as a major solvent and thus is crucial to cell function."},{"Start":"03:53.375 ","End":"03:55.940","Text":"E, we don\u0027t even need to look at because"},{"Start":"03:55.940 ","End":"03:58.100","Text":"that talks about all the sentences being correct,"},{"Start":"03:58.100 ","End":"03:59.825","Text":"and it isn\u0027t the case."},{"Start":"03:59.825 ","End":"04:01.325","Text":"C is the correct answer."},{"Start":"04:01.325 ","End":"04:05.990","Text":"We changed these sentences so that they are true as well."},{"Start":"04:05.990 ","End":"04:08.555","Text":"Now, all of these are true,"},{"Start":"04:08.555 ","End":"04:12.330","Text":"and we have completed this exercise."}],"ID":28334},{"Watched":false,"Name":"Exercise 2","Duration":"1m 39s","ChapterTopicVideoID":27213,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.200 ","End":"00:04.770","Text":"Hi there. Welcome to an exercise within the chapter"},{"Start":"00:04.770 ","End":"00:08.610","Text":"on Water in this section talking about water molecule,"},{"Start":"00:08.610 ","End":"00:10.440","Text":"structure, and properties."},{"Start":"00:10.440 ","End":"00:16.035","Text":"Name properties of water that contribute to its major role for cell function and life."},{"Start":"00:16.035 ","End":"00:17.730","Text":"We\u0027ve talked about a few things."},{"Start":"00:17.730 ","End":"00:19.875","Text":"Water is a major component in the cell."},{"Start":"00:19.875 ","End":"00:23.263","Text":"A cell is composed of 70-95 percent water,"},{"Start":"00:23.263 ","End":"00:26.550","Text":"and it is crucial since its properties affect the structure and"},{"Start":"00:26.550 ","End":"00:30.225","Text":"function of all other cellular constituents."},{"Start":"00:30.225 ","End":"00:34.380","Text":"The forces of attraction between water molecules and the slight tendency of water to"},{"Start":"00:34.380 ","End":"00:38.745","Text":"ionize are of crucial importance to the structure and function of a biomolecule."},{"Start":"00:38.745 ","End":"00:43.050","Text":"Both water molecules and water ionization products, H+ and OH-,"},{"Start":"00:43.050 ","End":"00:45.710","Text":"greatly influenced the structure, self-assembly,"},{"Start":"00:45.710 ","End":"00:48.605","Text":"and properties of all cellular components."},{"Start":"00:48.605 ","End":"00:55.490","Text":"These charges, even within the neutral water molecule that has polarity,"},{"Start":"00:55.490 ","End":"00:58.400","Text":"affects the structure and assembly."},{"Start":"00:58.400 ","End":"01:02.690","Text":"Now the noncovalent interactions responsible for the strength and specificity of"},{"Start":"01:02.690 ","End":"01:07.325","Text":"recognition among biomolecules are influenced by water\u0027s properties as a solvent,"},{"Start":"01:07.325 ","End":"01:11.690","Text":"including its ability to form hydrogen bonds with itself and with solids."},{"Start":"01:11.690 ","End":"01:13.640","Text":"We didn\u0027t really introduce this term,"},{"Start":"01:13.640 ","End":"01:17.360","Text":"but it is those bonds that we saw between"},{"Start":"01:17.360 ","End":"01:22.310","Text":"the positively charged hydrogen pole"},{"Start":"01:22.310 ","End":"01:28.250","Text":"with the negative pole of the oxygen of a second water molecule."},{"Start":"01:28.250 ","End":"01:30.920","Text":"With this, we completed this exercise."},{"Start":"01:30.920 ","End":"01:34.220","Text":"If you have more things to contribute to add to this,"},{"Start":"01:34.220 ","End":"01:39.390","Text":"feel free because there are other things we mentioned."}],"ID":28335},{"Watched":false,"Name":"Exercise 3","Duration":"54s","ChapterTopicVideoID":27212,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.020","Text":"Hi there. We\u0027re here with an exercise in the chapter of Water,"},{"Start":"00:04.020 ","End":"00:05.340","Text":"covering the water molecule,"},{"Start":"00:05.340 ","End":"00:07.500","Text":"structure, and properties."},{"Start":"00:07.500 ","End":"00:09.120","Text":"Based on this section,"},{"Start":"00:09.120 ","End":"00:14.760","Text":"what can be said about water with regard to human\u0027s total body weight and its importance?"},{"Start":"00:14.760 ","End":"00:18.750","Text":"Water makes up 60-75 percent of human body weight."},{"Start":"00:18.750 ","End":"00:21.105","Text":"Remember, the cell is 70-95 percent,"},{"Start":"00:21.105 ","End":"00:25.110","Text":"but it is 60-75 percent of human body weight."},{"Start":"00:25.110 ","End":"00:29.820","Text":"A loss of just 4 percent of total body water leads to dehydration,"},{"Start":"00:29.820 ","End":"00:35.809","Text":"while a loss of 15 percent of total body water can be fatal."},{"Start":"00:35.809 ","End":"00:39.650","Text":"We also mentioned that a person could survive a month without"},{"Start":"00:39.650 ","End":"00:43.955","Text":"food but wouldn\u0027t survive 3 days without water."},{"Start":"00:43.955 ","End":"00:51.617","Text":"That gives a clear comparison of the essential role that water plays."},{"Start":"00:51.617 ","End":"00:55.170","Text":"With that, we completed this exercise."}],"ID":28336},{"Watched":false,"Name":"Exercise 4","Duration":"1m 29s","ChapterTopicVideoID":27216,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.035","Text":"Hi there. Welcome back to another exercise within the chapter covering water,"},{"Start":"00:04.035 ","End":"00:07.980","Text":"in the section covering the water molecule structure and its properties."},{"Start":"00:07.980 ","End":"00:10.470","Text":"Describe the structure of the water molecule."},{"Start":"00:10.470 ","End":"00:14.100","Text":"We said that it is a simple molecule."},{"Start":"00:14.100 ","End":"00:17.130","Text":"Water is a polar molecule that is composed of"},{"Start":"00:17.130 ","End":"00:20.160","Text":"2 small positively charged hydrogen atoms and"},{"Start":"00:20.160 ","End":"00:24.585","Text":"1 large central negatively charged oxygen atom."},{"Start":"00:24.585 ","End":"00:26.730","Text":"When the hydrogens bind to the oxygen,"},{"Start":"00:26.730 ","End":"00:29.860","Text":"it creates an asymmetrical molecule with positive charge on 1 side,"},{"Start":"00:29.860 ","End":"00:32.760","Text":"on 1 pole and negative charge on the other side."},{"Start":"00:32.760 ","End":"00:36.060","Text":"This charge differential is called polarity and is"},{"Start":"00:36.060 ","End":"00:40.290","Text":"what dictates how water interacts with other molecules."},{"Start":"00:40.290 ","End":"00:44.900","Text":"As a reminder, we had the oxygen molecule that has the 2 negative"},{"Start":"00:44.900 ","End":"00:49.640","Text":"because it has the 2 electrons"},{"Start":"00:49.640 ","End":"00:56.090","Text":"orbiting with the negative charge and it has"},{"Start":"00:56.090 ","End":"01:02.585","Text":"the 2 hydrogen atoms which are actually positive,"},{"Start":"01:02.585 ","End":"01:06.885","Text":"with this side being the positively charge."},{"Start":"01:06.885 ","End":"01:14.450","Text":"That forms this tetrahedral shape."},{"Start":"01:14.450 ","End":"01:19.055","Text":"This actually should be dashed because it\u0027s not an actual bond,"},{"Start":"01:19.055 ","End":"01:21.700","Text":"rather the electrons are orbiting."},{"Start":"01:21.700 ","End":"01:27.170","Text":"This is what allows interactions with other polar molecules and with that,"},{"Start":"01:27.170 ","End":"01:30.300","Text":"we\u0027ve completed this exercise."}],"ID":28337},{"Watched":false,"Name":"Bonding Ability","Duration":"7m 40s","ChapterTopicVideoID":27219,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.044","Text":"Hi, there. We are in the chapter,"},{"Start":"00:03.044 ","End":"00:07.635","Text":"basics of water talking about bonding ability."},{"Start":"00:07.635 ","End":"00:09.720","Text":"By the end of this section, you should be able to"},{"Start":"00:09.720 ","End":"00:12.015","Text":"understand water\u0027s function as a solvent,"},{"Start":"00:12.015 ","End":"00:14.130","Text":"define the terms solvent, solute,"},{"Start":"00:14.130 ","End":"00:15.360","Text":"and aqueous solution,"},{"Start":"00:15.360 ","End":"00:18.315","Text":"and describe weak interactions in aqueous systems."},{"Start":"00:18.315 ","End":"00:21.030","Text":"The forces of attraction between water molecules,"},{"Start":"00:21.030 ","End":"00:24.980","Text":"and the slight tendency of water to ionize are of"},{"Start":"00:24.980 ","End":"00:29.870","Text":"crucial importance to the structure and function of biomolecules."},{"Start":"00:29.870 ","End":"00:32.240","Text":"Not only the water molecule itself,"},{"Start":"00:32.240 ","End":"00:35.810","Text":"rather also its water ionization products H"},{"Start":"00:35.810 ","End":"00:39.560","Text":"plus and OH minus greatly influenced the structure,"},{"Start":"00:39.560 ","End":"00:44.720","Text":"self-assembly, and properties of all cellular components including proteins,"},{"Start":"00:44.720 ","End":"00:46.820","Text":"nucleic acids, and lipids."},{"Start":"00:46.820 ","End":"00:51.350","Text":"The non-covalent interactions responsible for the strength and specificity of"},{"Start":"00:51.350 ","End":"00:56.420","Text":"recognition among biomolecules are influenced by water\u0027s properties as a solvent,"},{"Start":"00:56.420 ","End":"01:01.580","Text":"including its ability to form hydrogen bonds with itself and with solids."},{"Start":"01:01.580 ","End":"01:07.250","Text":"These are weak interactions because they\u0027re non-covalent in aqueous systems,"},{"Start":"01:07.250 ","End":"01:10.760","Text":"meaning systems that are based on water."},{"Start":"01:10.760 ","End":"01:12.800","Text":"Just introduce this in a little more detail"},{"Start":"01:12.800 ","End":"01:15.140","Text":"before we really dive into the nitty-gritty in the next sections,"},{"Start":"01:15.140 ","End":"01:18.905","Text":"how water plays a role of a participant in the cell."},{"Start":"01:18.905 ","End":"01:21.380","Text":"Let\u0027s go over some definitions and then cover"},{"Start":"01:21.380 ","End":"01:23.945","Text":"the concept of weak interactions in aqueous systems."},{"Start":"01:23.945 ","End":"01:26.179","Text":"Here you\u0027re just seeing water."},{"Start":"01:26.179 ","End":"01:30.905","Text":"This is an aqueous system because it\u0027s a system that\u0027s based on water."},{"Start":"01:30.905 ","End":"01:34.285","Text":"You have these water molecules 1, 2."},{"Start":"01:34.285 ","End":"01:36.935","Text":"As I mentioned in the previous section,"},{"Start":"01:36.935 ","End":"01:39.410","Text":"you have the negative charge,"},{"Start":"01:39.410 ","End":"01:41.990","Text":"the negative pole of the oxygen that can"},{"Start":"01:41.990 ","End":"01:47.720","Text":"interact with the positive charge of the hydrogen."},{"Start":"01:47.720 ","End":"01:50.000","Text":"This is called the hydrogen bond."},{"Start":"01:50.000 ","End":"01:52.370","Text":"Weak interactions in aqueous systems."},{"Start":"01:52.370 ","End":"01:57.500","Text":"A solution is a liquid consisting of 2 or more substances evenly mixed."},{"Start":"01:57.500 ","End":"02:01.130","Text":"The dissolving agent is called the solvent,"},{"Start":"02:01.130 ","End":"02:05.020","Text":"and the dissolved substance is called the solute."},{"Start":"02:05.020 ","End":"02:07.980","Text":"When water is the solvent,"},{"Start":"02:07.980 ","End":"02:11.610","Text":"the result is called an aqueous solution,"},{"Start":"02:11.610 ","End":"02:17.730","Text":"and is marked by this, lowercase (aq)."},{"Start":"02:17.730 ","End":"02:21.620","Text":"Now, hydrogen bonds"},{"Start":"02:21.620 ","End":"02:26.270","Text":"between water molecules provide the cohesive forces that make water liquid at"},{"Start":"02:26.270 ","End":"02:30.485","Text":"room temperature and a crystalline solid-ice"},{"Start":"02:30.485 ","End":"02:36.155","Text":"with a highly ordered arrangement of molecules at cold temperatures."},{"Start":"02:36.155 ","End":"02:38.659","Text":"As a result of water\u0027s polarity,"},{"Start":"02:38.659 ","End":"02:41.990","Text":"each water molecule attracts other water molecules because of"},{"Start":"02:41.990 ","End":"02:47.000","Text":"the opposite charges between water molecules forming these hydrogen bonds."},{"Start":"02:47.000 ","End":"02:49.700","Text":"Hydrogen because the positive charge of the hydrogen"},{"Start":"02:49.700 ","End":"02:54.105","Text":"interact with the negative charge of the oxygen."},{"Start":"02:54.105 ","End":"02:59.270","Text":"Polar biomolecules dissolve readily in"},{"Start":"02:59.270 ","End":"03:04.130","Text":"water because polar means they also have these pseudo charges,"},{"Start":"03:04.130 ","End":"03:05.935","Text":"these polls that are charged."},{"Start":"03:05.935 ","End":"03:07.625","Text":"They can do this."},{"Start":"03:07.625 ","End":"03:10.970","Text":"These polar biomarkers can dissolve in water because they can replace"},{"Start":"03:10.970 ","End":"03:16.340","Text":"the water interactions with water solute interactions."},{"Start":"03:16.340 ","End":"03:19.910","Text":"The water-water interactions can be replaced with"},{"Start":"03:19.910 ","End":"03:23.741","Text":"more energetically favorable water solid interaction."},{"Start":"03:23.741 ","End":"03:26.690","Text":"Saying it differently, hydrogen bonds allow"},{"Start":"03:26.690 ","End":"03:30.245","Text":"ions and other polar molecules to dissolve in water."},{"Start":"03:30.245 ","End":"03:32.330","Text":"Therefore, water is an excellent solvent."},{"Start":"03:32.330 ","End":"03:36.490","Text":"What happens is we have NaCl."},{"Start":"03:36.490 ","End":"03:40.325","Text":"A polar biomolecule salt,"},{"Start":"03:40.325 ","End":"03:43.280","Text":"and we have the water molecules that are polar."},{"Start":"03:43.280 ","End":"03:50.370","Text":"What will happen is that the ion of the NaCl,"},{"Start":"03:50.370 ","End":"03:53.215","Text":"the negative, the chlorine,"},{"Start":"03:53.215 ","End":"03:58.145","Text":"will interact with the hydrogens of the water,"},{"Start":"03:58.145 ","End":"04:01.730","Text":"while the sodium that\u0027s positively charged will interact with"},{"Start":"04:01.730 ","End":"04:07.735","Text":"a negatively charged poles of the water molecule, the oxygens."},{"Start":"04:07.735 ","End":"04:12.890","Text":"This replaces these attraction forces that otherwise"},{"Start":"04:12.890 ","End":"04:18.460","Text":"these hydrogen bonds that otherwise are formed between water molecules."},{"Start":"04:18.460 ","End":"04:22.850","Text":"Since most biological molecules have some electrical asymmetry,"},{"Start":"04:22.850 ","End":"04:24.410","Text":"they too are polar,"},{"Start":"04:24.410 ","End":"04:28.980","Text":"and water molecules can form bonds and surround"},{"Start":"04:28.980 ","End":"04:31.550","Text":"both their positive and negative regions in the act of"},{"Start":"04:31.550 ","End":"04:35.045","Text":"surrounding the polar molecules of another substance."},{"Start":"04:35.045 ","End":"04:38.300","Text":"Water wiggles its way into all the nooks and crannies between"},{"Start":"04:38.300 ","End":"04:42.260","Text":"the molecules effectively breaking it apart and dissolving it."},{"Start":"04:42.260 ","End":"04:44.330","Text":"We saw the example of salt of NaCl,"},{"Start":"04:44.330 ","End":"04:46.115","Text":"let\u0027s give another example."},{"Start":"04:46.115 ","End":"04:51.345","Text":"This is what happens when you put sugar crystals in water."},{"Start":"04:51.345 ","End":"04:53.420","Text":"Both water and sugar are polar allowing"},{"Start":"04:53.420 ","End":"04:57.240","Text":"individual water molecules to surround individual sugar molecules."},{"Start":"04:57.240 ","End":"04:59.710","Text":"You have the sugar here in white and the water in blue."},{"Start":"04:59.710 ","End":"05:07.660","Text":"You\u0027d have sugar that was put into this water solutions, aqueous solution."},{"Start":"05:07.660 ","End":"05:11.600","Text":"Basically, you will see that these water molecules will"},{"Start":"05:11.600 ","End":"05:15.185","Text":"then interact and surround the individual sugar molecules,"},{"Start":"05:15.185 ","End":"05:18.950","Text":"breaking apart this sugar and dissolving it as it"},{"Start":"05:18.950 ","End":"05:24.365","Text":"spreads and each sugar is surrounded by water molecules."},{"Start":"05:24.365 ","End":"05:26.705","Text":"Now, similar to polarity,"},{"Start":"05:26.705 ","End":"05:28.400","Text":"some molecules are made of ions,"},{"Start":"05:28.400 ","End":"05:30.290","Text":"or oppositely charged particles."},{"Start":"05:30.290 ","End":"05:33.800","Text":"Water breaks apart these ionic molecules as well by"},{"Start":"05:33.800 ","End":"05:37.705","Text":"interacting with both positively and negatively charged particles."},{"Start":"05:37.705 ","End":"05:41.180","Text":"Example, this is what happens when you"},{"Start":"05:41.180 ","End":"05:45.230","Text":"put salt in water because salt is composed of sodium and chloride."},{"Start":"05:45.230 ","End":"05:47.045","Text":"Remember, we had that before."},{"Start":"05:47.045 ","End":"05:50.180","Text":"We\u0027ll expand on the different types of bonds in a following topic."},{"Start":"05:50.180 ","End":"05:56.215","Text":"But what you see here is dissolving of salt in water."},{"Start":"05:56.215 ","End":"06:01.710","Text":"Remember, we had the Na plus and Cl minus,"},{"Start":"06:01.710 ","End":"06:09.620","Text":"and what happens is the water interacts and breaks apart these ions and surrounds it."},{"Start":"06:09.620 ","End":"06:13.870","Text":"There\u0027s dissociation of ionic compounds in the solvent."},{"Start":"06:13.870 ","End":"06:16.160","Text":"Nonpolar biomolecules on the other hand,"},{"Start":"06:16.160 ","End":"06:21.555","Text":"are pretty soluble in water because they interfere with water-water interactions,"},{"Start":"06:21.555 ","End":"06:25.070","Text":"but are unable to form water solute interactions,"},{"Start":"06:25.070 ","End":"06:26.720","Text":"thus an aqueous solution,"},{"Start":"06:26.720 ","End":"06:30.500","Text":"they tend to cluster together."},{"Start":"06:30.500 ","End":"06:35.045","Text":"We have polar molecules interrupt"},{"Start":"06:35.045 ","End":"06:42.650","Text":"water molecules from associating with each other and replace as well as ions,"},{"Start":"06:42.650 ","End":"06:46.190","Text":"ionic molecules, and replace the water- water interaction"},{"Start":"06:46.190 ","End":"06:49.610","Text":"with the water solute interaction."},{"Start":"06:49.610 ","End":"06:55.145","Text":"Whereas the nonpolar biomolecules are pretty soluble."},{"Start":"06:55.145 ","End":"06:57.080","Text":"They interfere with the water-water interactions,"},{"Start":"06:57.080 ","End":"07:02.930","Text":"but don\u0027t replace these interactions,"},{"Start":"07:02.930 ","End":"07:06.950","Text":"therefore, they tend to cluster together and not dissolve."},{"Start":"07:06.950 ","End":"07:11.930","Text":"With this week covered bonding ability within the chapter of water,"},{"Start":"07:11.930 ","End":"07:15.920","Text":"we should now be able to understand water\u0027s function as a solvent,"},{"Start":"07:15.920 ","End":"07:17.180","Text":"define the term solvent,"},{"Start":"07:17.180 ","End":"07:19.070","Text":"solute, and aqueous solution."},{"Start":"07:19.070 ","End":"07:23.600","Text":"To remind you this is a way to write solution."},{"Start":"07:23.600 ","End":"07:28.640","Text":"If you write NaCl aqueous like this,"},{"Start":"07:28.640 ","End":"07:31.655","Text":"it means NaCl is dissolved in water,"},{"Start":"07:31.655 ","End":"07:35.170","Text":"and you should be able to describe weak interactions in aqueous systems."},{"Start":"07:35.170 ","End":"07:40.560","Text":"We will further get into this in the following sections and topics."}],"ID":28338},{"Watched":false,"Name":"Exercise 5","Duration":"3m 19s","ChapterTopicVideoID":27220,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.110 ","End":"00:05.805","Text":"Hey there, welcome back to an exercise covering bonding ability."},{"Start":"00:05.805 ","End":"00:08.940","Text":"Which of the following statement is false?"},{"Start":"00:08.940 ","End":"00:11.970","Text":"A, water is the universal solvent."},{"Start":"00:11.970 ","End":"00:16.032","Text":"B, water destabilizes temperature."},{"Start":"00:16.032 ","End":"00:18.630","Text":"C, water is essential for life."},{"Start":"00:18.630 ","End":"00:23.910","Text":"D, water cohesive and adhesive properties are responsible for surface tension."},{"Start":"00:23.910 ","End":"00:28.620","Text":"We talked about water being a very good solvent."},{"Start":"00:28.620 ","End":"00:33.960","Text":"Anything that\u0027s polar or ions can actually dissolve in water"},{"Start":"00:33.960 ","End":"00:39.090","Text":"and it is considered the universal solvent so this is true therefore,"},{"Start":"00:39.090 ","End":"00:41.370","Text":"this can\u0027t be the correct answer."},{"Start":"00:41.370 ","End":"00:44.914","Text":"B, water destabilizes temperature."},{"Start":"00:44.914 ","End":"00:47.285","Text":"We talked about different properties of water,"},{"Start":"00:47.285 ","End":"00:51.154","Text":"including the fact that water has"},{"Start":"00:51.154 ","End":"00:56.930","Text":"these hydrogen bonds that affects its colligative properties,"},{"Start":"00:56.930 ","End":"00:59.015","Text":"its vapor, its boiling point,"},{"Start":"00:59.015 ","End":"01:04.845","Text":"all kinds of things that have to also do with temperature."},{"Start":"01:04.845 ","End":"01:13.835","Text":"In a way, we can say that water actually stabilizes temperature so this may be false."},{"Start":"01:13.835 ","End":"01:17.190","Text":"Let\u0027s hop over to the next ones and see what we see."},{"Start":"01:17.190 ","End":"01:20.170","Text":"C, water is essential for life."},{"Start":"01:20.170 ","End":"01:23.720","Text":"Well, this, we know we started the chapter talking"},{"Start":"01:23.720 ","End":"01:27.500","Text":"about water being a major component in cells,"},{"Start":"01:27.500 ","End":"01:28.910","Text":"a major component in organisms."},{"Start":"01:28.910 ","End":"01:30.950","Text":"It\u0027s a major component on Earth."},{"Start":"01:30.950 ","End":"01:33.755","Text":"It is essential for life."},{"Start":"01:33.755 ","End":"01:37.025","Text":"So C, we know is true,"},{"Start":"01:37.025 ","End":"01:41.585","Text":"therefore it cannot be false so this won\u0027t be correct."},{"Start":"01:41.585 ","End":"01:43.370","Text":"Let\u0027s move on to D. Water"},{"Start":"01:43.370 ","End":"01:48.185","Text":"cohesive and adhesive properties are responsible for surface tension."},{"Start":"01:48.185 ","End":"01:51.635","Text":"Again, cohesive and adhesive properties has to do with"},{"Start":"01:51.635 ","End":"01:58.505","Text":"the hydrogen bonds and basically other non-covalent bonds that occur"},{"Start":"01:58.505 ","End":"02:04.070","Text":"within the water molecules and these do"},{"Start":"02:04.070 ","End":"02:10.760","Text":"create the stickiness of water molecules that creates a surface tension."},{"Start":"02:10.760 ","End":"02:14.795","Text":"We mentioned that these can float therefore on top of the water."},{"Start":"02:14.795 ","End":"02:22.205","Text":"This sounds like it is a statement that we introduced in the chapter."},{"Start":"02:22.205 ","End":"02:26.885","Text":"This is statement that seems true and we\u0027ve talked about in the chapter,"},{"Start":"02:26.885 ","End":"02:30.860","Text":"so we can say this is not a false statement as well,"},{"Start":"02:30.860 ","End":"02:35.095","Text":"so we will cross off D and that leaves us with B"},{"Start":"02:35.095 ","End":"02:40.270","Text":"remaining the statement we would say is false, water destabilizes temperature."},{"Start":"02:40.270 ","End":"02:45.290","Text":"Again, this is because some of these properties that are mentioned, if anything,"},{"Start":"02:45.290 ","End":"02:48.800","Text":"we could say the temperature is more stable with water and that is"},{"Start":"02:48.800 ","End":"02:54.290","Text":"another reason it is important and conducive of life."},{"Start":"02:54.290 ","End":"02:57.890","Text":"It helps organisms maintain a certain temperature,"},{"Start":"02:57.890 ","End":"03:01.580","Text":"which is important for functioning and for many,"},{"Start":"03:01.580 ","End":"03:04.264","Text":"many processes in an organism."},{"Start":"03:04.264 ","End":"03:07.310","Text":"Furthermore, by stabilizing temperature in water,"},{"Start":"03:07.310 ","End":"03:11.510","Text":"it is also something that allows for life to exist in"},{"Start":"03:11.510 ","End":"03:16.705","Text":"oceans and waters from where we also are believed to have evolved from."},{"Start":"03:16.705 ","End":"03:20.020","Text":"With this, we\u0027ve concluded this exercise."}],"ID":28339},{"Watched":false,"Name":"Exercise 6","Duration":"4m 31s","ChapterTopicVideoID":27221,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.500","Text":"Hey there, welcome to an exercise within the section"},{"Start":"00:04.500 ","End":"00:09.510","Text":"of bonding ability in the basics of water."},{"Start":"00:09.510 ","End":"00:15.945","Text":"Match between each item of A through C to its corresponding description in 1 through 3."},{"Start":"00:15.945 ","End":"00:18.690","Text":"A, hydrogen bonds."},{"Start":"00:18.690 ","End":"00:21.467","Text":"B, polar biomolecules."},{"Start":"00:21.467 ","End":"00:23.550","Text":"C, nonpolar biomolecules."},{"Start":"00:23.550 ","End":"00:25.845","Text":"Let\u0027s go through 1 to 3."},{"Start":"00:25.845 ","End":"00:30.120","Text":"One, these tend to cluster together and are poorly soluble in water because they"},{"Start":"00:30.120 ","End":"00:34.770","Text":"interfere with water-water interactions while unable to form water-solute interactions,"},{"Start":"00:34.770 ","End":"00:37.695","Text":"which ones poorly soluble in water."},{"Start":"00:37.695 ","End":"00:41.390","Text":"These provide the cohesive forces that make water liquid at room temperature and"},{"Start":"00:41.390 ","End":"00:45.005","Text":"a crystalline solid ice at cold temperatures."},{"Start":"00:45.005 ","End":"00:49.340","Text":"Three, these readily dissolve in water because they can replace"},{"Start":"00:49.340 ","End":"00:55.460","Text":"the water-water interaction with more energetically favorable water-solute interactions."},{"Start":"00:55.460 ","End":"00:57.739","Text":"Hydrogen bonds."},{"Start":"00:57.739 ","End":"00:59.195","Text":"What did we learn about these?"},{"Start":"00:59.195 ","End":"01:02.870","Text":"These are those interactions between,"},{"Start":"01:02.870 ","End":"01:04.385","Text":"we gave examples in water,"},{"Start":"01:04.385 ","End":"01:09.800","Text":"the positive charge of the hydrogen on"},{"Start":"01:09.800 ","End":"01:18.815","Text":"positive pole of the water molecule with a negative charge of the oxygen."},{"Start":"01:18.815 ","End":"01:21.770","Text":"These are hydrogen bonds."},{"Start":"01:21.770 ","End":"01:29.760","Text":"We talked about this allows such molecules to interact with each other."},{"Start":"01:31.060 ","End":"01:36.910","Text":"Not necessarily this, maybe this and not sure with this."},{"Start":"01:36.910 ","End":"01:38.659","Text":"Let\u0027s go to polar biomolecules."},{"Start":"01:38.659 ","End":"01:43.760","Text":"We talked about, water molecules interact and create these bonds,"},{"Start":"01:43.760 ","End":"01:47.540","Text":"these relationships because of this polarity."},{"Start":"01:47.540 ","End":"01:50.270","Text":"Remember the polarity is the idea that,"},{"Start":"01:50.270 ","End":"01:52.085","Text":"even if it\u0027s a neutral molecule,"},{"Start":"01:52.085 ","End":"01:56.795","Text":"that there is some pool with the charges,"},{"Start":"01:56.795 ","End":"01:59.945","Text":"like there\u0027s a side of the molecule that"},{"Start":"01:59.945 ","End":"02:05.240","Text":"is more positive and another side that may be more negative."},{"Start":"02:05.240 ","End":"02:07.700","Text":"This would be a polar bond molecule and"},{"Start":"02:07.700 ","End":"02:14.869","Text":"polar biomolecules interact with other polar biomolecules better."},{"Start":"02:14.869 ","End":"02:19.520","Text":"This would be water, as an example,"},{"Start":"02:19.520 ","End":"02:25.495","Text":"that can interact with itself and also with other polar molecules."},{"Start":"02:25.495 ","End":"02:29.570","Text":"If we look, these tend to cluster together and are poorly soluble in"},{"Start":"02:29.570 ","End":"02:31.190","Text":"water because they interfere with"},{"Start":"02:31.190 ","End":"02:34.525","Text":"water-water interactions while unable to form water-solute interactions."},{"Start":"02:34.525 ","End":"02:38.815","Text":"This can\u0027t be true for polar because polar can form."},{"Start":"02:38.815 ","End":"02:41.930","Text":"Two, these provide the cohesive forces that make water liquid at"},{"Start":"02:41.930 ","End":"02:45.420","Text":"room temperature and crystalline solid ice at cold temperatures."},{"Start":"02:45.490 ","End":"02:50.630","Text":"Maybe the polarity and the interactions."},{"Start":"02:50.630 ","End":"02:53.870","Text":"Three, these readily dissolve in water because they can replace"},{"Start":"02:53.870 ","End":"02:58.265","Text":"the water-water interactions with more energetically favorable water-solute interactions."},{"Start":"02:58.265 ","End":"03:02.215","Text":"This sounds like the definition for polar."},{"Start":"03:02.215 ","End":"03:06.510","Text":"I would say B goes with 3."},{"Start":"03:06.510 ","End":"03:08.140","Text":"Then we go back to 1."},{"Start":"03:08.140 ","End":"03:12.145","Text":"These tend to cluster together and are poorly soluble in water."},{"Start":"03:12.145 ","End":"03:16.790","Text":"These would be the opposite of the description of polar."},{"Start":"03:16.790 ","End":"03:20.350","Text":"Therefore, this sounds like non-polar."},{"Start":"03:20.350 ","End":"03:23.390","Text":"That leaves us with A and 2. Let\u0027s verify."},{"Start":"03:23.390 ","End":"03:27.950","Text":"Hydrogen bonds, these bonds that we know that exists between water molecules,"},{"Start":"03:27.950 ","End":"03:34.700","Text":"we had mentioned it can associate and cause water to have"},{"Start":"03:34.700 ","End":"03:38.615","Text":"this bonding ability where it actually"},{"Start":"03:38.615 ","End":"03:43.610","Text":"is liquid at room temperature and a solid at cold temperature."},{"Start":"03:43.610 ","End":"03:47.180","Text":"These associations give it the viscosity,"},{"Start":"03:47.180 ","End":"03:49.410","Text":"make it cohesive;"},{"Start":"03:49.410 ","End":"03:54.940","Text":"so A will go with 2."},{"Start":"03:54.940 ","End":"03:56.480","Text":"Let\u0027s go with this."},{"Start":"03:56.480 ","End":"03:58.369","Text":"We\u0027ve got hydrogen bonds."},{"Start":"03:58.369 ","End":"04:01.790","Text":"These provide the cohesive forces that make water liquid at room temperature and"},{"Start":"04:01.790 ","End":"04:06.530","Text":"crystalline solid ice at cold temperatures, said polar biomolecules,"},{"Start":"04:06.530 ","End":"04:08.000","Text":"these readily dissolve,"},{"Start":"04:08.000 ","End":"04:10.190","Text":"so B with 3,"},{"Start":"04:10.190 ","End":"04:13.190","Text":"these readily dissolve in water because they can replace the water-water interactions"},{"Start":"04:13.190 ","End":"04:16.640","Text":"with a more energetically favorable water solute interactions."},{"Start":"04:16.640 ","End":"04:19.885","Text":"That leaves us with C going with 1,"},{"Start":"04:19.885 ","End":"04:22.310","Text":"nonpolar biomolecules tend to cluster"},{"Start":"04:22.310 ","End":"04:25.220","Text":"together and are poorly soluble in water because they interfere with"},{"Start":"04:25.220 ","End":"04:28.190","Text":"water-water interactions while unable to form"},{"Start":"04:28.190 ","End":"04:32.460","Text":"water-soluble interactions and there you have it."}],"ID":28340},{"Watched":false,"Name":"Exercise 7","Duration":"1m 31s","ChapterTopicVideoID":27217,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.290 ","End":"00:09.255","Text":"Hey there, welcome back to an exercise covering the topic of bonding ability of water."},{"Start":"00:09.255 ","End":"00:12.600","Text":"Part 1, define the term solution,"},{"Start":"00:12.600 ","End":"00:16.230","Text":"solvent, and solute."},{"Start":"00:16.230 ","End":"00:24.285","Text":"A solution is a liquid consisting of 2 or more substances, evenly mixed."},{"Start":"00:24.285 ","End":"00:26.820","Text":"Solution, again,"},{"Start":"00:26.820 ","End":"00:31.335","Text":"it\u0027s a liquid consisting of 2 or more substances that are mixed together."},{"Start":"00:31.335 ","End":"00:36.360","Text":"The dissolving agent in the solution is called the solvent,"},{"Start":"00:36.360 ","End":"00:39.240","Text":"the one we gave an example of a solution is"},{"Start":"00:39.240 ","End":"00:42.225","Text":"a liquid consisting of 2 or more substances that are mixed."},{"Start":"00:42.225 ","End":"00:46.990","Text":"The dissolving agent is called the solvent and the dissolved is a solute."},{"Start":"00:46.990 ","End":"00:49.610","Text":"Part 2, when water is the solvent,"},{"Start":"00:49.610 ","End":"00:52.610","Text":"what is the liquid it results in?"},{"Start":"00:52.610 ","End":"01:01.020","Text":"We gave a term and let\u0027s think about when you think of water in different languages,"},{"Start":"01:01.020 ","End":"01:06.765","Text":"or Aquaman, we think aqua,"},{"Start":"01:06.765 ","End":"01:12.605","Text":"so this is a clue and the result is called an"},{"Start":"01:12.605 ","End":"01:19.865","Text":"aqueous solution and the symbol for it is (aq)."},{"Start":"01:19.865 ","End":"01:23.990","Text":"So think of water, aqua,"},{"Start":"01:23.990 ","End":"01:25.670","Text":"it is the solvent, therefore,"},{"Start":"01:25.670 ","End":"01:28.925","Text":"it\u0027s a solution, aqueous solution."},{"Start":"01:28.925 ","End":"01:31.800","Text":"Let\u0027s move on to the next exercise."}],"ID":28341},{"Watched":false,"Name":"Exercise 8","Duration":"2m 19s","ChapterTopicVideoID":27218,"CourseChapterTopicPlaylistID":268846,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.020 ","End":"00:04.530","Text":"Hey there. We\u0027re exploring our knowledge within the section of"},{"Start":"00:04.530 ","End":"00:10.972","Text":"bonding ability in the topic of the basics of water in the chapter about water."},{"Start":"00:10.972 ","End":"00:13.365","Text":"Let\u0027s dive in. Part 1."},{"Start":"00:13.365 ","End":"00:17.505","Text":"Please explain how water dissolves other substances."},{"Start":"00:17.505 ","End":"00:20.070","Text":"We mentioned this a couple of times."},{"Start":"00:20.070 ","End":"00:24.510","Text":"Polar by molecule dissolve in water because they can replace the water-water interactions"},{"Start":"00:24.510 ","End":"00:29.910","Text":"with more energetically favorable water solute interactions."},{"Start":"00:29.910 ","End":"00:34.770","Text":"Water can dissolve polar biomolecules and it"},{"Start":"00:34.770 ","End":"00:39.315","Text":"has the ability to dissolve them most types of liquids."},{"Start":"00:39.315 ","End":"00:42.860","Text":"In other words, water molecules can form bonds with and surround"},{"Start":"00:42.860 ","End":"00:45.172","Text":"the polar molecules of another substance"},{"Start":"00:45.172 ","End":"00:48.335","Text":"effectively breaking the substance apart and dissolving it."},{"Start":"00:48.335 ","End":"00:51.005","Text":"We gave the example of salt, NaCl,"},{"Start":"00:51.005 ","End":"00:54.830","Text":"sodium chloride, and the example of sugar."},{"Start":"00:54.830 ","End":"00:58.370","Text":"Let\u0027s go to Part 2. Give an example of this."},{"Start":"00:58.370 ","End":"01:01.715","Text":"Most biological molecules have some electrical asymmetry,"},{"Start":"01:01.715 ","End":"01:07.190","Text":"so they too are polar and thus water molecules can form bonds with an surround"},{"Start":"01:07.190 ","End":"01:10.130","Text":"both their positive and negative regions because water"},{"Start":"01:10.130 ","End":"01:13.520","Text":"also has a positive pole and a negative pole."},{"Start":"01:13.520 ","End":"01:16.325","Text":"It also has the charged regions."},{"Start":"01:16.325 ","End":"01:20.345","Text":"In the act of surrounding the polar molecules of this other substance,"},{"Start":"01:20.345 ","End":"01:23.390","Text":"water wiggles its way into all the nooks and crannies between"},{"Start":"01:23.390 ","End":"01:27.755","Text":"molecules effectively breaking it apart and dissolving it."},{"Start":"01:27.755 ","End":"01:32.345","Text":"It associates with the charges of"},{"Start":"01:32.345 ","End":"01:38.405","Text":"these other molecules and surrounds it and then breaks apart the substance."},{"Start":"01:38.405 ","End":"01:41.675","Text":"This is what happens when you put sugar crystals in water."},{"Start":"01:41.675 ","End":"01:44.315","Text":"Both water and sugar are polar,"},{"Start":"01:44.315 ","End":"01:45.605","Text":"this works for salt as well,"},{"Start":"01:45.605 ","End":"01:50.120","Text":"allowing individual water molecules to surround individual sugar molecules,"},{"Start":"01:50.120 ","End":"01:52.520","Text":"breaking apart the sugar and dissolving it."},{"Start":"01:52.520 ","End":"01:55.730","Text":"We introduced another figure for it,"},{"Start":"01:55.730 ","End":"02:00.860","Text":"if you remember, where there was the cup and the water molecules were, blue,"},{"Start":"02:00.860 ","End":"02:03.560","Text":"sugar was this white gray,"},{"Start":"02:03.560 ","End":"02:05.720","Text":"and then in time,"},{"Start":"02:05.720 ","End":"02:12.825","Text":"you saw the water molecules surrounding these sugar molecules."},{"Start":"02:12.825 ","End":"02:15.960","Text":"This is what happens in essence."},{"Start":"02:15.960 ","End":"02:19.110","Text":"With this, we completed this exercise."}],"ID":28342}],"Thumbnail":null,"ID":268846},{"Name":"Weak Noncovalent Interactions","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Exercise 1","Duration":"1m 33s","ChapterTopicVideoID":27624,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.915","Text":"Hi there, welcome to Hydrogen Bonds and we are going to start with this exercise."},{"Start":"00:06.915 ","End":"00:10.590","Text":"Which bond represents a weak chemical bond?"},{"Start":"00:10.590 ","End":"00:14.415","Text":"Hydrogen bonds, B, nonpolar covalent bond,"},{"Start":"00:14.415 ","End":"00:16.695","Text":"C, covalent bond,"},{"Start":"00:16.695 ","End":"00:19.820","Text":"D, polar covalent bond."},{"Start":"00:19.820 ","End":"00:25.445","Text":"As the name of the topic is weak non-covalent interactions."},{"Start":"00:25.445 ","End":"00:34.480","Text":"We could probably say it would not be a covalent bond that is considered the weak."},{"Start":"00:34.480 ","End":"00:38.210","Text":"Even though if we look at hydrogen bond,"},{"Start":"00:38.210 ","End":"00:39.710","Text":"nonpolar covalent bonds,"},{"Start":"00:39.710 ","End":"00:41.300","Text":"and polar covalent bond."},{"Start":"00:41.300 ","End":"00:45.020","Text":"Hydrogen bond we know is a non-covalent bond."},{"Start":"00:45.020 ","End":"00:50.000","Text":"Non-covalent bond will be weaker than a covalent bond"},{"Start":"00:50.000 ","End":"00:55.055","Text":"even if we mentioned non-polar covalent bond or polar covalent bond."},{"Start":"00:55.055 ","End":"00:59.390","Text":"The key here is that it is a covalent bond."},{"Start":"00:59.390 ","End":"01:01.790","Text":"Therefore, we can cross out"},{"Start":"01:01.790 ","End":"01:05.630","Text":"this non-polar covalent bond because it\u0027s still a covalent bond,"},{"Start":"01:05.630 ","End":"01:08.995","Text":"we can cross out a covalent bond,"},{"Start":"01:08.995 ","End":"01:14.735","Text":"and we also can cross out the polar covalent bond."},{"Start":"01:14.735 ","End":"01:18.290","Text":"As the name of the topic is weak non-covalent interactions."},{"Start":"01:18.290 ","End":"01:25.670","Text":"We can eliminate all that fall under the covalent bond category and that leaves"},{"Start":"01:25.670 ","End":"01:34.770","Text":"us with hydrogen bond as the correct answer because it is a non-covalent bond."}],"ID":28855},{"Watched":false,"Name":"Exercise 2","Duration":"1m 31s","ChapterTopicVideoID":27625,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.020 ","End":"00:04.410","Text":"Hi there, welcome back to an exercise within hydrogen bonds,"},{"Start":"00:04.410 ","End":"00:08.845","Text":"in the topic of non-covalent weak interactions."},{"Start":"00:08.845 ","End":"00:11.385","Text":"We are going to drill this concept in."},{"Start":"00:11.385 ","End":"00:13.980","Text":"What is a characteristic of water that results in"},{"Start":"00:13.980 ","End":"00:17.685","Text":"the cohesive forces that make water a liquid at room temperature,"},{"Start":"00:17.685 ","End":"00:19.540","Text":"and a crystalline solid,"},{"Start":"00:19.540 ","End":"00:24.060","Text":"and organized array of the water molecules,"},{"Start":"00:24.060 ","End":"00:27.715","Text":"ice, at cold temperatures?"},{"Start":"00:27.715 ","End":"00:30.560","Text":"The answer to that is hydrogen bonds."},{"Start":"00:30.560 ","End":"00:32.810","Text":"Hydrogen bonds between water molecules provide"},{"Start":"00:32.810 ","End":"00:36.350","Text":"the cohesive forces that make water a liquid at room temperature,"},{"Start":"00:36.350 ","End":"00:38.045","Text":"and a crystalline solid, ice,"},{"Start":"00:38.045 ","End":"00:43.205","Text":"with a highly ordered arrangement of molecules at cold temperatures."},{"Start":"00:43.205 ","End":"00:45.215","Text":"If we look here at the figure,"},{"Start":"00:45.215 ","End":"00:47.330","Text":"we can see this is gas phase,"},{"Start":"00:47.330 ","End":"00:49.220","Text":"it has no hydrogen bonds."},{"Start":"00:49.220 ","End":"00:57.650","Text":"Liquid phase, this already is a cohesive form because it\u0027s connected in this puddle,"},{"Start":"00:57.650 ","End":"01:01.670","Text":"and this is where you have the cohesive forces,"},{"Start":"01:01.670 ","End":"01:05.630","Text":"the hydrogen bonds contributing to attraction and constant,"},{"Start":"01:05.630 ","End":"01:12.520","Text":"continuous bonding and detachment of these water molecules from each other."},{"Start":"01:12.520 ","End":"01:17.660","Text":"Then you have the ice crystalline solid phase of water,"},{"Start":"01:17.660 ","End":"01:22.460","Text":"where the strong hydrogen bonds between organized that"},{"Start":"01:22.460 ","End":"01:28.385","Text":"each water molecule forms 4 bonds and we get this organized lattice."},{"Start":"01:28.385 ","End":"01:31.950","Text":"That was another exercise within hydrogen bonds."}],"ID":28856},{"Watched":false,"Name":"Exercise 3","Duration":"56s","ChapterTopicVideoID":27626,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:01.740","Text":"Here we are again,"},{"Start":"00:01.740 ","End":"00:06.150","Text":"testing our knowledge on hydrogen bonds."},{"Start":"00:06.150 ","End":"00:09.630","Text":"Complete the sentence and explain why: Water in"},{"Start":"00:09.630 ","End":"00:13.545","Text":"comparison to other common solvents has a blank."},{"Start":"00:13.545 ","End":"00:19.265","Text":"Melting point, boiling point, and heat vaporization."},{"Start":"00:19.265 ","End":"00:22.100","Text":"Basically, what we said is that water,"},{"Start":"00:22.100 ","End":"00:24.290","Text":"in comparison to other common solvents,"},{"Start":"00:24.290 ","End":"00:26.420","Text":"we know that these, compared to methanol,"},{"Start":"00:26.420 ","End":"00:28.745","Text":"butanol, et cetera are higher,"},{"Start":"00:28.745 ","End":"00:31.730","Text":"so it has a higher melting point,"},{"Start":"00:31.730 ","End":"00:33.990","Text":"boiling point, and heat vaporization,"},{"Start":"00:33.990 ","End":"00:40.475","Text":"and we know that this is as a result of the hydrogen bonds between the water molecules."},{"Start":"00:40.475 ","End":"00:45.440","Text":"The hydrogen bonds between water molecules cause the water to have a high heat capacity."},{"Start":"00:45.440 ","End":"00:50.450","Text":"The forces of attraction of hydrogen bonds require higher input of energy to disperse,"},{"Start":"00:50.450 ","End":"00:55.070","Text":"to spread the water molecules so that they melt, boil, or evaporate."},{"Start":"00:55.070 ","End":"00:57.570","Text":"Let\u0027s move to another exercise."}],"ID":28857},{"Watched":false,"Name":"Exercise 4","Duration":"1m 3s","ChapterTopicVideoID":27627,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:07.215","Text":"Hi there. We are checking our understanding of hydrogen bonds with another exercise."},{"Start":"00:07.215 ","End":"00:11.055","Text":"Define and explain the term cohesion."},{"Start":"00:11.055 ","End":"00:16.455","Text":"In general, cohesion can be defined as the action or fact of forming a united whole,"},{"Start":"00:16.455 ","End":"00:22.094","Text":"like, \"the work at present lacks cohesion\" meaning unity, continuity, etc."},{"Start":"00:22.094 ","End":"00:28.665","Text":"But in science, cohesion is the sticking together of particles of the same substance."},{"Start":"00:28.665 ","End":"00:30.180","Text":"In regard to water,"},{"Start":"00:30.180 ","End":"00:32.700","Text":"hydrogen bonds cause water molecules to"},{"Start":"00:32.700 ","End":"00:36.015","Text":"stick together giving water a high surface tension,"},{"Start":"00:36.015 ","End":"00:41.870","Text":"which allows things to stay on top and not break the surface."},{"Start":"00:41.870 ","End":"00:44.390","Text":"With surface tension, meaning the measure of how"},{"Start":"00:44.390 ","End":"00:47.527","Text":"difficult it is to stretch or break the surface of a liquid."},{"Start":"00:47.527 ","End":"00:49.655","Text":"For water, it is high, therefore,"},{"Start":"00:49.655 ","End":"00:53.090","Text":"certain organisms and materials can land, stand,"},{"Start":"00:53.090 ","End":"00:58.730","Text":"and walk on the water as seen by these insects."},{"Start":"00:58.730 ","End":"01:02.880","Text":"We also showed floaties, etc."}],"ID":28858},{"Watched":false,"Name":"Exercise 5","Duration":"2m 23s","ChapterTopicVideoID":27628,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.605","Text":"Hi, we\u0027re back with practice questions covering the topic of hydrogen bonds."},{"Start":"00:04.605 ","End":"00:06.600","Text":"Which of the following statement is true?"},{"Start":"00:06.600 ","End":"00:10.710","Text":"A, hydrogen bonds are shorter than covalent bonds."},{"Start":"00:10.710 ","End":"00:16.665","Text":"B, hydrogen bonds are responsible for cohesive properties of water."},{"Start":"00:16.665 ","End":"00:22.740","Text":"C, ice is more dense than liquid water since it has more hydrogen bonds per molecule."},{"Start":"00:22.740 ","End":"00:27.795","Text":"D, covalent bonds are the weakest bond."},{"Start":"00:27.795 ","End":"00:32.265","Text":"E, none of the above is true. Let\u0027s go over this again."},{"Start":"00:32.265 ","End":"00:35.445","Text":"Hydrogen bonds are shorter than covalent bonds."},{"Start":"00:35.445 ","End":"00:42.120","Text":"Well, we generally said that hydrogen bonds are a non-covalent bond,"},{"Start":"00:42.120 ","End":"00:45.890","Text":"meaning it\u0027s weaker and when something is weaker,"},{"Start":"00:45.890 ","End":"00:48.554","Text":"it actually doesn\u0027t pull it in as strongly,"},{"Start":"00:48.554 ","End":"00:52.159","Text":"therefore it would probably be longer,"},{"Start":"00:52.159 ","End":"00:55.870","Text":"but before I select this one,"},{"Start":"00:55.870 ","End":"00:57.320","Text":"let\u0027s see the other ones."},{"Start":"00:57.320 ","End":"01:02.974","Text":"Hydrogen bonds are responsible for cohesive properties of water."},{"Start":"01:02.974 ","End":"01:08.360","Text":"Well, that sounds true to me because we did say the hydrogen bonds"},{"Start":"01:08.360 ","End":"01:16.515","Text":"are a big contribution or have responsibility for the cohesive properties of water."},{"Start":"01:16.515 ","End":"01:18.650","Text":"This seems true to me."},{"Start":"01:18.650 ","End":"01:22.435","Text":"This seems untrue, so I will already say A is untrue."},{"Start":"01:22.435 ","End":"01:26.580","Text":"We talked about ice being less dense than liquid,"},{"Start":"01:26.580 ","End":"01:30.065","Text":"which is why it floats to the top and why in lakes and"},{"Start":"01:30.065 ","End":"01:35.305","Text":"oceans it allows for viability, survival of organisms."},{"Start":"01:35.305 ","End":"01:37.695","Text":"This to me is not true,"},{"Start":"01:37.695 ","End":"01:40.650","Text":"I would say is out."},{"Start":"01:40.650 ","End":"01:43.280","Text":"Then we go into covalent bonds again,"},{"Start":"01:43.280 ","End":"01:46.670","Text":"we talked about these are the weakest bond and actually,"},{"Start":"01:46.670 ","End":"01:51.585","Text":"we mentioned that non-covalent bonds are the weakest."},{"Start":"01:51.585 ","End":"01:57.250","Text":"This seems to be untrue as well and since B"},{"Start":"01:57.250 ","End":"02:00.020","Text":"sounds to be true to us because hydrogen bonds are"},{"Start":"02:00.020 ","End":"02:02.870","Text":"responsible for cohesive properties of water,"},{"Start":"02:02.870 ","End":"02:04.190","Text":"I would say that\u0027s true, therefore,"},{"Start":"02:04.190 ","End":"02:06.065","Text":"I would say E is untrue,"},{"Start":"02:06.065 ","End":"02:09.425","Text":"and that leaves us with B,"},{"Start":"02:09.425 ","End":"02:13.355","Text":"Hydrogen bonds are responsible for cohesive properties of water,"},{"Start":"02:13.355 ","End":"02:17.735","Text":"which are essential for many different things."},{"Start":"02:17.735 ","End":"02:24.090","Text":"Let\u0027s break it up and reconvene with the next exercise."}],"ID":28859},{"Watched":false,"Name":"Exercise 6","Duration":"1m 29s","ChapterTopicVideoID":27629,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.150","Text":"Hopefully, after these practice questions,"},{"Start":"00:03.150 ","End":"00:07.020","Text":"you will be feeling more and more confident about hydrogen bonds."},{"Start":"00:07.020 ","End":"00:10.815","Text":"Name a few attributes of liquid water with regard to hydrogen bonds."},{"Start":"00:10.815 ","End":"00:13.860","Text":"Now you can name any of the things that we mentioned."},{"Start":"00:13.860 ","End":"00:16.470","Text":"I\u0027m going to go over a few here."},{"Start":"00:16.470 ","End":"00:18.210","Text":"At any given time,"},{"Start":"00:18.210 ","End":"00:21.455","Text":"most of the molecules in liquid water are hydrogen-bonded."},{"Start":"00:21.455 ","End":"00:28.335","Text":"If you remember, we talked about 3.4 ever-changing bonding and dissociating."},{"Start":"00:28.335 ","End":"00:34.995","Text":"The lifetime of each hydrogen bond is a mere 1-20 picoseconds."},{"Start":"00:34.995 ","End":"00:39.525","Text":"Reminder, 1 picosecond is 10^-12 seconds,"},{"Start":"00:39.525 ","End":"00:41.694","Text":"meaning very, very short time."},{"Start":"00:41.694 ","End":"00:45.740","Text":"Furthermore, when 1 hydrogen bond breaks another hydrogen bond forms with"},{"Start":"00:45.740 ","End":"00:50.045","Text":"the same partner or a new one within 0.1 picoseconds."},{"Start":"00:50.045 ","End":"00:51.890","Text":"In essence, it\u0027s immediate,"},{"Start":"00:51.890 ","End":"00:53.540","Text":"it\u0027s at the same time."},{"Start":"00:53.540 ","End":"00:56.735","Text":"Now the phrase flickering clusters, it\u0027s flickering,"},{"Start":"00:56.735 ","End":"01:00.410","Text":"it\u0027s going on and off all the time has been applied to the short-lived groups of"},{"Start":"01:00.410 ","End":"01:04.320","Text":"water molecules interlinked by hydrogen bonds in liquid water."},{"Start":"01:04.320 ","End":"01:07.260","Text":"They are constantly forming and dissociating,"},{"Start":"01:07.260 ","End":"01:09.559","Text":"so these are flickering clusters."},{"Start":"01:09.559 ","End":"01:13.190","Text":"Another attribute of liquid water with regard to hydrogen bonds is that the sum of"},{"Start":"01:13.190 ","End":"01:15.590","Text":"all hydrogen bonds between water molecules confers"},{"Start":"01:15.590 ","End":"01:18.170","Text":"great internal cohesion on liquid water,"},{"Start":"01:18.170 ","End":"01:21.665","Text":"even though when we look at the hydrogen bond individually,"},{"Start":"01:21.665 ","End":"01:25.215","Text":"it is considered a weak non-covalent bond."},{"Start":"01:25.215 ","End":"01:30.250","Text":"That is a wrap on this exercise."}],"ID":28860},{"Watched":false,"Name":"Exercise 7","Duration":"2m 34s","ChapterTopicVideoID":27643,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.000","Text":"Hey, there. Welcome to an exercise covering"},{"Start":"00:03.000 ","End":"00:07.930","Text":"the topic and section of electrostatic ionic bonds."},{"Start":"00:08.660 ","End":"00:10.965","Text":"Which of the following is true?"},{"Start":"00:10.965 ","End":"00:14.370","Text":"A, water is a polar solvent, B,"},{"Start":"00:14.370 ","End":"00:18.420","Text":"water readily dissolves charged or polar compounds,"},{"Start":"00:18.420 ","End":"00:22.430","Text":"C, most biomolecules fall into this category,"},{"Start":"00:22.430 ","End":"00:25.890","Text":"and D, all of the above."},{"Start":"00:26.860 ","End":"00:29.750","Text":"Let\u0027s start with A,"},{"Start":"00:29.750 ","End":"00:34.230","Text":"water is a polar solvent. This sounds true."},{"Start":"00:34.230 ","End":"00:38.490","Text":"We talk about water being a solvent and water is a polar molecule."},{"Start":"00:38.490 ","End":"00:41.930","Text":"Remember H_2O, you have the oxygen with"},{"Start":"00:41.930 ","End":"00:49.700","Text":"the partial negative charge and the hydrogens that have the partial positive charges,"},{"Start":"00:49.700 ","End":"00:56.870","Text":"and therefore you have a polar molecule and is a very good solvent."},{"Start":"00:56.870 ","End":"00:58.385","Text":"This one is true."},{"Start":"00:58.385 ","End":"01:02.159","Text":"But before we select A, let\u0027s check the other ones."},{"Start":"01:02.159 ","End":"01:06.915","Text":"B, water readily dissolves charged or polar compounds."},{"Start":"01:06.915 ","End":"01:12.080","Text":"Water being a very common and good solvent,"},{"Start":"01:12.080 ","End":"01:15.170","Text":"it actually does dissolve compounds,"},{"Start":"01:15.170 ","End":"01:19.685","Text":"and which compounds that we mentioned dissolve well in a polar solvent,"},{"Start":"01:19.685 ","End":"01:23.960","Text":"it is charged or polar compounds."},{"Start":"01:23.960 ","End":"01:29.940","Text":"Charged or polar compounds or molecules are what dissolve well in a polar solvent,"},{"Start":"01:29.940 ","End":"01:31.235","Text":"in water, therefore,"},{"Start":"01:31.235 ","End":"01:32.660","Text":"this is true as well."},{"Start":"01:32.660 ","End":"01:35.330","Text":"Water readily dissolves charged or polar compounds."},{"Start":"01:35.330 ","End":"01:39.710","Text":"Let\u0027s look at c because we have 2 true statements,"},{"Start":"01:39.710 ","End":"01:42.900","Text":"and though we may want to just shortcut and jump to d,"},{"Start":"01:42.900 ","End":"01:44.025","Text":"all of the above,"},{"Start":"01:44.025 ","End":"01:48.425","Text":"we may find c is untrue and then we have to look better at our statements here."},{"Start":"01:48.425 ","End":"01:51.830","Text":"C, most biomolecules fall into this category,"},{"Start":"01:51.830 ","End":"01:55.915","Text":"in the above category of charged or polar compounds."},{"Start":"01:55.915 ","End":"02:00.920","Text":"Most biomolecules are polar or charged compounds,"},{"Start":"02:00.920 ","End":"02:02.570","Text":"actually polar compounds, therefore,"},{"Start":"02:02.570 ","End":"02:05.510","Text":"they do fall into this category of something that"},{"Start":"02:05.510 ","End":"02:09.180","Text":"dissolves readily in water being charged or polar,"},{"Start":"02:09.180 ","End":"02:11.690","Text":"and therefore this is true as well."},{"Start":"02:11.690 ","End":"02:17.045","Text":"We can now say choosing any one of these will be"},{"Start":"02:17.045 ","End":"02:24.200","Text":"incorrect when we have the option of D. We can say A is not what we want to choose here,"},{"Start":"02:24.200 ","End":"02:25.685","Text":"nor B nor C,"},{"Start":"02:25.685 ","End":"02:29.495","Text":"we want to go with D because all of the above are correct,"},{"Start":"02:29.495 ","End":"02:32.655","Text":"and that is the answer for this exercise,"},{"Start":"02:32.655 ","End":"02:34.900","Text":"let\u0027s move on to the next."}],"ID":28861},{"Watched":false,"Name":"Exercise 8","Duration":"1m 23s","ChapterTopicVideoID":27620,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.285","Text":"Welcome back to Electrostatic Ionic Bonds."},{"Start":"00:03.285 ","End":"00:05.190","Text":"We have another exercise."},{"Start":"00:05.190 ","End":"00:08.085","Text":"Define the terms hydrophilic and hydrophobic."},{"Start":"00:08.085 ","End":"00:10.785","Text":"Similar portion is hydro,"},{"Start":"00:10.785 ","End":"00:15.255","Text":"and the different portion is philic and phobic."},{"Start":"00:15.255 ","End":"00:21.105","Text":"Compounds that dissolve easily in water are termed hydrophilic."},{"Start":"00:21.105 ","End":"00:23.985","Text":"Hydro water from Greek,"},{"Start":"00:23.985 ","End":"00:26.175","Text":"philic, like love."},{"Start":"00:26.175 ","End":"00:31.335","Text":"This stems from Greek as much of the terminology and biology and science."},{"Start":"00:31.335 ","End":"00:32.850","Text":"Hydro, as we said,"},{"Start":"00:32.850 ","End":"00:35.415","Text":"is water and philos means love."},{"Start":"00:35.415 ","End":"00:38.760","Text":"Now hydrophilic therefore describes ions or"},{"Start":"00:38.760 ","End":"00:42.830","Text":"polar molecules that interact well with other polar molecules such as water."},{"Start":"00:42.830 ","End":"00:45.980","Text":"They enjoy, they like to interact,"},{"Start":"00:45.980 ","End":"00:49.700","Text":"they love to interact with water, hydrophilic."},{"Start":"00:49.700 ","End":"00:53.235","Text":"Hydrophobic on the other hand, you have phobic."},{"Start":"00:53.235 ","End":"00:55.175","Text":"Phobic is fear it describes"},{"Start":"00:55.175 ","End":"00:57.680","Text":"uncharged non-polar molecules that do"},{"Start":"00:57.680 ","End":"01:00.350","Text":"not interact well with polar molecules such as water."},{"Start":"01:00.350 ","End":"01:01.565","Text":"As you see here,"},{"Start":"01:01.565 ","End":"01:04.310","Text":"you have fat drops, oil drops,"},{"Start":"01:04.310 ","End":"01:06.050","Text":"and they do not dissolve,"},{"Start":"01:06.050 ","End":"01:07.835","Text":"they do not associate with the water,"},{"Start":"01:07.835 ","End":"01:11.195","Text":"the 2 phases, the 2 forms of liquid stay separate."},{"Start":"01:11.195 ","End":"01:14.075","Text":"Here we see these crystalline if it\u0027s salt or sugar,"},{"Start":"01:14.075 ","End":"01:17.060","Text":"they go into the water and they associate and this is"},{"Start":"01:17.060 ","End":"01:20.760","Text":"why it seems like it\u0027s disappearing because it\u0027s dissolving."},{"Start":"01:20.760 ","End":"01:23.850","Text":"Let\u0027s move on to the next exercise."}],"ID":28862},{"Watched":false,"Name":"Exercise 9","Duration":"2m ","ChapterTopicVideoID":27621,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.685","Text":"Hi there, we\u0027re testing on knowledge covering the topic of electrostatic ionic bonds."},{"Start":"00:05.685 ","End":"00:12.880","Text":"Explain the interaction that enables water to dissolve polar substances such as salts."},{"Start":"00:13.340 ","End":"00:17.880","Text":"We talked about salt specifically sodium chloride, NaCl."},{"Start":"00:17.880 ","End":"00:20.670","Text":"Water dissolves polar salts such as NaCl,"},{"Start":"00:20.670 ","End":"00:23.250","Text":"sodium chloride by hydrating and stabilizing"},{"Start":"00:23.250 ","End":"00:27.780","Text":"the ions that it separates into Na^+ and Cl^-,"},{"Start":"00:27.780 ","End":"00:31.320","Text":"weakening the electrostatic interactions between them and thus"},{"Start":"00:31.320 ","End":"00:36.685","Text":"counteracting their tendency to associate in a crystalline lattice."},{"Start":"00:36.685 ","End":"00:39.170","Text":"Explaining this a little bit."},{"Start":"00:39.170 ","End":"00:45.320","Text":"Further, it replaces the solute-solute hydrogen bonds,"},{"Start":"00:45.320 ","End":"00:51.320","Text":"linking these biomolecules to each other with solute-water hydrogen bonds."},{"Start":"00:51.320 ","End":"00:54.725","Text":"Therefore, this crystalline structure breaks."},{"Start":"00:54.725 ","End":"01:01.580","Text":"When salts dissolve and break away from the crystal lattice and form"},{"Start":"01:01.580 ","End":"01:08.255","Text":"into ions such as sodium Na^+ and chloride Cl^-,"},{"Start":"01:08.255 ","End":"01:11.915","Text":"they acquire greater freedom of motion."},{"Start":"01:11.915 ","End":"01:14.839","Text":"This results in an increase in entropy,"},{"Start":"01:14.839 ","End":"01:17.150","Text":"which is why this is favorable."},{"Start":"01:17.150 ","End":"01:19.940","Text":"In other words, the resulting increase in entropy,"},{"Start":"01:19.940 ","End":"01:23.600","Text":"randomness S of the system is largely"},{"Start":"01:23.600 ","End":"01:27.965","Text":"responsible for the ease of dissolving salts in water."},{"Start":"01:27.965 ","End":"01:33.665","Text":"You have crystalline lattice of salt and it breaks"},{"Start":"01:33.665 ","End":"01:40.115","Text":"apart because what you have is instead of having the solute-solute interaction,"},{"Start":"01:40.115 ","End":"01:44.990","Text":"water comes and there is replacement with solute-water interaction."},{"Start":"01:44.990 ","End":"01:48.290","Text":"The crystalline structure is broken apart."},{"Start":"01:48.290 ","End":"01:52.370","Text":"The ions are broken and they acquire greater freedom of motion"},{"Start":"01:52.370 ","End":"01:54.530","Text":"because they have this interaction with"},{"Start":"01:54.530 ","End":"01:58.025","Text":"the hydrogen molecules and therefore entropy increases."},{"Start":"01:58.025 ","End":"02:01.320","Text":"That is for this exercise."}],"ID":28863},{"Watched":false,"Name":"Exercise 10","Duration":"2m 9s","ChapterTopicVideoID":27622,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.330","Text":"What have you learned about electrostatic and ionic bonds?"},{"Start":"00:03.330 ","End":"00:08.250","Text":"What are the 3 factors that contribute to the strength of ionic interactions?"},{"Start":"00:08.250 ","End":"00:11.250","Text":"We talked about a formula and we mentioned the strength of"},{"Start":"00:11.250 ","End":"00:15.030","Text":"force F of ionic interactions in solution"},{"Start":"00:15.030 ","End":"00:22.170","Text":"depends on the magnitude of the charges of the ions that are formed,"},{"Start":"00:22.170 ","End":"00:26.595","Text":"the distance between the charged groups r,"},{"Start":"00:26.595 ","End":"00:32.230","Text":"and the dielectric constant Epsilon of the solvent in which the interactions occur."},{"Start":"00:32.230 ","End":"00:35.375","Text":"We mentioned that the dielectric constant is actually"},{"Start":"00:35.375 ","End":"00:40.655","Text":"ability or the favoring of dissolving in the solvent."},{"Start":"00:40.655 ","End":"00:44.180","Text":"The dielectric constant is a quantity measuring the ability of"},{"Start":"00:44.180 ","End":"00:47.465","Text":"a substance to store electrical energy in an electric field."},{"Start":"00:47.465 ","End":"00:51.200","Text":"Another way to explain it is a higher dielectric constant of"},{"Start":"00:51.200 ","End":"00:55.700","Text":"the solvent correlates with a higher ability of the solvent to dissolve salts."},{"Start":"00:55.700 ","End":"00:58.975","Text":"Now the formula representing this relationship is F for"},{"Start":"00:58.975 ","End":"01:03.725","Text":"force Q_1Q_2 is the magnitude of the charges,"},{"Start":"01:03.725 ","End":"01:07.280","Text":"because when you have an ionic interaction,"},{"Start":"01:07.280 ","End":"01:11.485","Text":"you will have a positive ion and a negative ion interacting."},{"Start":"01:11.485 ","End":"01:13.919","Text":"In the case of NaCl,"},{"Start":"01:13.919 ","End":"01:17.100","Text":"it\u0027s Na^plus and Cl^minus."},{"Start":"01:17.100 ","End":"01:19.440","Text":"These are the ions that they interact,"},{"Start":"01:19.440 ","End":"01:25.459","Text":"so the Q_1 and Q_2 are the magnitude of each of these charges."},{"Start":"01:25.459 ","End":"01:26.750","Text":"This would be, for example 1,"},{"Start":"01:26.750 ","End":"01:28.740","Text":"this would be 2, they\u0027re opposite,"},{"Start":"01:28.740 ","End":"01:33.830","Text":"and the dielectric constant Epsilon of the solvent in which the interactions occur."},{"Start":"01:33.830 ","End":"01:35.810","Text":"This would be of the water,"},{"Start":"01:35.810 ","End":"01:37.790","Text":"which is a good solvent."},{"Start":"01:37.790 ","End":"01:41.685","Text":"Force equals the magnitude of the 2 charges of the ions"},{"Start":"01:41.685 ","End":"01:46.220","Text":"and the distance between the charged group if they are very attracted to each other,"},{"Start":"01:46.220 ","End":"01:48.910","Text":"it would be very close to each other."},{"Start":"01:48.910 ","End":"01:51.470","Text":"Then you have the Epsilon,"},{"Start":"01:51.470 ","End":"01:54.020","Text":"which is the dielectric constant of the solvent."},{"Start":"01:54.020 ","End":"02:02.765","Text":"Those are the 3 factors that contribute to the strength of ionic interactions."},{"Start":"02:02.765 ","End":"02:05.870","Text":"Now try to remember that formula because that will"},{"Start":"02:05.870 ","End":"02:10.140","Text":"help you remember the 3 contributors to the force."}],"ID":28864},{"Watched":false,"Name":"Exercise 11","Duration":"5m 46s","ChapterTopicVideoID":27623,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.140 ","End":"00:05.430","Text":"Hi there. We are going over concepts we learned in the lesson about"},{"Start":"00:05.430 ","End":"00:10.440","Text":"electrostatic ionic bonds and seeing what we know about these."},{"Start":"00:10.440 ","End":"00:15.465","Text":"Which is false about Nonpolar Gases?"},{"Start":"00:15.465 ","End":"00:18.810","Text":"We covered this in Part 2."},{"Start":"00:18.810 ","End":"00:22.695","Text":"A, these are poorly soluble in water."},{"Start":"00:22.695 ","End":"00:25.980","Text":"B, the molecules of the biologically important gases,"},{"Start":"00:25.980 ","End":"00:27.359","Text":"carbon dioxide, oxygen,"},{"Start":"00:27.359 ","End":"00:29.745","Text":"and nitrogen are nonpolar."},{"Start":"00:29.745 ","End":"00:32.520","Text":"C, the change of such molecules from the"},{"Start":"00:32.520 ","End":"00:35.820","Text":"disordered gas phase into aqueous solution constraints"},{"Start":"00:35.820 ","End":"00:38.010","Text":"their motion and the motion of water molecules,"},{"Start":"00:38.010 ","End":"00:40.725","Text":"thus resulting in a decrease in entropy."},{"Start":"00:40.725 ","End":"00:45.544","Text":"D, all organisms have water-soluble carrier proteins,"},{"Start":"00:45.544 ","End":"00:49.070","Text":"such as hemoglobin and myoglobin that facilitate the transport of"},{"Start":"00:49.070 ","End":"00:51.680","Text":"nonpolar molecules and this allows"},{"Start":"00:51.680 ","End":"00:55.585","Text":"the transport and utilization of such molecules for biological functions."},{"Start":"00:55.585 ","End":"00:59.375","Text":"E, 2 phases form when they\u0027re mixed with water,"},{"Start":"00:59.375 ","End":"01:02.510","Text":"neither liquid is soluble in the other."},{"Start":"01:02.510 ","End":"01:08.110","Text":"F, nonpolar compounds are hydrophobic."},{"Start":"01:08.110 ","End":"01:10.625","Text":"A, nonpolar gases."},{"Start":"01:10.625 ","End":"01:13.340","Text":"These are poorly soluble in water."},{"Start":"01:13.340 ","End":"01:19.460","Text":"Yeah. We mentioned that constantly the polar molecules are"},{"Start":"01:19.460 ","End":"01:25.490","Text":"soluble in polar solvents and water is a polar solvent therefore,"},{"Start":"01:25.490 ","End":"01:28.220","Text":"nonpolar molecules like nonpolar gases,"},{"Start":"01:28.220 ","End":"01:29.510","Text":"are poorly soluble in water."},{"Start":"01:29.510 ","End":"01:31.264","Text":"Therefore, this is true,"},{"Start":"01:31.264 ","End":"01:34.220","Text":"meaning it is incorrect as"},{"Start":"01:34.220 ","End":"01:37.625","Text":"we\u0027re looking for something that\u0027s false. Let\u0027s cross that out."},{"Start":"01:37.625 ","End":"01:41.450","Text":"B, the molecules of the biologically important gases,"},{"Start":"01:41.450 ","End":"01:44.660","Text":"CO_2, O_2 and nitrogen are nonpolar."},{"Start":"01:44.660 ","End":"01:47.390","Text":"We mentioned these examples specifically,"},{"Start":"01:47.390 ","End":"01:50.500","Text":"also showed 2 other examples in the table that we didn\u0027t focus on,"},{"Start":"01:50.500 ","End":"01:53.390","Text":"but we specifically mentioned these as being"},{"Start":"01:53.390 ","End":"02:01.600","Text":"nonpolar gases because we have showed even that CO_2 has the double bond,"},{"Start":"02:01.600 ","End":"02:07.255","Text":"that keeps it somewhat linear and therefore, it is nonpolar."},{"Start":"02:07.255 ","End":"02:10.795","Text":"Oxygen has the double bond between it,"},{"Start":"02:10.795 ","End":"02:16.480","Text":"nonpolar and nitrogen with the triple bond also is nonpolar,"},{"Start":"02:16.480 ","End":"02:20.380","Text":"and we even mentioned and reminded how water is polar"},{"Start":"02:20.380 ","End":"02:25.720","Text":"because oxygen has a more negative polar charge,"},{"Start":"02:25.720 ","End":"02:29.290","Text":"it has these electrons that are orbiting and"},{"Start":"02:29.290 ","End":"02:33.010","Text":"pushes crowds that hydrogens together and there you have"},{"Start":"02:33.010 ","End":"02:36.670","Text":"these 2 partial positive charges to"},{"Start":"02:36.670 ","End":"02:41.895","Text":"the sides and the partial negative charge on the oxygen."},{"Start":"02:41.895 ","End":"02:46.040","Text":"We can say that this is an example of"},{"Start":"02:46.040 ","End":"02:50.480","Text":"nonpolar gases and therefore this is a true statement,"},{"Start":"02:50.480 ","End":"02:54.215","Text":"hence it is incorrect to say this is false."},{"Start":"02:54.215 ","End":"02:56.905","Text":"Crossing this out. C,"},{"Start":"02:56.905 ","End":"02:59.540","Text":"the change of such molecules from the disordered gas"},{"Start":"02:59.540 ","End":"03:03.110","Text":"phase into aqueous solution constraints"},{"Start":"03:03.110 ","End":"03:08.945","Text":"their motion and the motion of water molecules thus resulting in a decrease in entropy."},{"Start":"03:08.945 ","End":"03:15.770","Text":"Gas phase being disordered because here they\u0027re nonpolar and now into"},{"Start":"03:15.770 ","End":"03:18.955","Text":"aqueous solution constraining their motion"},{"Start":"03:18.955 ","End":"03:22.670","Text":"and the motion of water molecules results in a decrease in entropy."},{"Start":"03:22.670 ","End":"03:28.115","Text":"We kind of talked of the hydrophobic effect and that these cages that are formed."},{"Start":"03:28.115 ","End":"03:32.665","Text":"Again, this is true."},{"Start":"03:32.665 ","End":"03:34.755","Text":"This is not our answer."},{"Start":"03:34.755 ","End":"03:36.950","Text":"D, all organisms have"},{"Start":"03:36.950 ","End":"03:38.990","Text":"water-soluble carrier proteins such as"},{"Start":"03:38.990 ","End":"03:41.630","Text":"hemoglobin and myoglobin that facilitate the transport of"},{"Start":"03:41.630 ","End":"03:45.140","Text":"nonpolar molecules and this allows the transport and utilization of"},{"Start":"03:45.140 ","End":"03:49.700","Text":"such molecules for biological functions like oxygen, it is not soluble."},{"Start":"03:49.700 ","End":"03:52.855","Text":"How does it get around where it has carrier proteins?"},{"Start":"03:52.855 ","End":"03:57.370","Text":"We didn\u0027t say that all organisms have these,"},{"Start":"03:57.370 ","End":"04:02.835","Text":"so I would question this one as being the correct answer,"},{"Start":"04:02.835 ","End":"04:10.410","Text":"I\u0027m not sure that this is true so I\u0027m going to put very beautiful question mark here."},{"Start":"04:10.410 ","End":"04:13.370","Text":"E, 2 phases form when they are mixed with water,"},{"Start":"04:13.370 ","End":"04:15.005","Text":"neither liquid is soluble in the other."},{"Start":"04:15.005 ","End":"04:21.395","Text":"Remember we talked about putting oil or something that is nonpolar,"},{"Start":"04:21.395 ","End":"04:23.675","Text":"something that is hydrophobic,"},{"Start":"04:23.675 ","End":"04:31.775","Text":"and being that the nonpolar gases are non-soluble in water,"},{"Start":"04:31.775 ","End":"04:34.010","Text":"this can be true about this,"},{"Start":"04:34.010 ","End":"04:36.620","Text":"they will stay separate."},{"Start":"04:36.620 ","End":"04:40.900","Text":"To me, this sounds like a true statement again."},{"Start":"04:40.900 ","End":"04:45.670","Text":"Therefore, it doesn\u0027t qualify as our answer,"},{"Start":"04:45.670 ","End":"04:49.160","Text":"so I will eliminate E. Last but not least,"},{"Start":"04:49.160 ","End":"04:52.280","Text":"nonpolar compounds are hydrophobic."},{"Start":"04:52.280 ","End":"04:54.290","Text":"Going over all these A, B,"},{"Start":"04:54.290 ","End":"04:56.540","Text":"C, even D, and E,"},{"Start":"04:56.540 ","End":"04:59.015","Text":"we know nonpolar compounds are hydrophobic,"},{"Start":"04:59.015 ","End":"05:01.700","Text":"therefore, we also talked about the hydrophobic effect, etc."},{"Start":"05:01.700 ","End":"05:04.235","Text":"This is also true."},{"Start":"05:04.235 ","End":"05:10.690","Text":"Eliminating that, that leaves us with D as the false 1."},{"Start":"05:11.570 ","End":"05:15.530","Text":"All organisms have water-soluble carrier proteins such as hemoglobin"},{"Start":"05:15.530 ","End":"05:18.718","Text":"and myoglobin that facilitate the transport of nonpolar molecules,"},{"Start":"05:18.718 ","End":"05:23.040","Text":"and this allows the transport and utilization of such molecules for biological functions."},{"Start":"05:23.040 ","End":"05:26.480","Text":"That is a [inaudible] It would be correct if it said"},{"Start":"05:26.480 ","End":"05:31.280","Text":"some organisms have water-soluble carrier proteins such as hemoglobin and myoglobin"},{"Start":"05:31.280 ","End":"05:34.370","Text":"that facilitate the transport of nonpolar molecules like"},{"Start":"05:34.370 ","End":"05:38.300","Text":"oxygen throughout the body where CO_2"},{"Start":"05:38.300 ","End":"05:47.100","Text":"to get rid of it and this is important for biological functions. That\u0027s a wrap."}],"ID":28865},{"Watched":false,"Name":"Ampipathic compounds","Duration":"11m 1s","ChapterTopicVideoID":27630,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:01.350","Text":"By the end of this section,"},{"Start":"00:01.350 ","End":"00:05.085","Text":"you will be able to define what an amphipathic compound,"},{"Start":"00:05.085 ","End":"00:08.010","Text":"non amphipathic, explain the role and significance of"},{"Start":"00:08.010 ","End":"00:12.075","Text":"such compounds and the hydrophobic effect."},{"Start":"00:12.075 ","End":"00:19.409","Text":"Amphipathic molecules or chemical compounds that contain polar or charged and nonpolar,"},{"Start":"00:19.409 ","End":"00:23.550","Text":"apolar regions or portions in their structure."},{"Start":"00:23.550 ","End":"00:26.790","Text":"Synonym is amphiphilic."},{"Start":"00:26.790 ","End":"00:27.915","Text":"Now if you remember,"},{"Start":"00:27.915 ","End":"00:30.269","Text":"we talked about hydrophilic,"},{"Start":"00:30.269 ","End":"00:34.425","Text":"love, amphiphilic, so loves."},{"Start":"00:34.425 ","End":"00:39.680","Text":"We should know philic is love from Greek language as mentioned before,"},{"Start":"00:39.680 ","End":"00:43.250","Text":"an example of this is phospholipids."},{"Start":"00:43.250 ","End":"00:47.840","Text":"We had introduced these in the first chapter,"},{"Start":"00:47.840 ","End":"00:51.305","Text":"in earlier sections, where you have a hydrophilic head,"},{"Start":"00:51.305 ","End":"00:54.200","Text":"it interacts with water, the hydrophobic tail."},{"Start":"00:54.200 ","End":"00:57.515","Text":"We even mentioned these terms and defined them in the previous section,"},{"Start":"00:57.515 ","End":"01:01.719","Text":"this does not associate with water."},{"Start":"01:01.719 ","End":"01:04.549","Text":"These are examples,"},{"Start":"01:04.549 ","End":"01:07.250","Text":"a phospholipid is an amphiphilic,"},{"Start":"01:07.250 ","End":"01:13.215","Text":"an amphipathic compound because it has both a polar,"},{"Start":"01:13.215 ","End":"01:15.195","Text":"a charged area,"},{"Start":"01:15.195 ","End":"01:18.995","Text":"and a non-polar, apolar region."},{"Start":"01:18.995 ","End":"01:22.970","Text":"Just mentioned that briefly before and we\u0027ll go into it more systematic."},{"Start":"01:22.970 ","End":"01:28.565","Text":"The term amphipathic came from the Greek language as many of our words in biology."},{"Start":"01:28.565 ","End":"01:32.880","Text":"Amphis, both, and Patheia, suffering/feeling."},{"Start":"01:33.430 ","End":"01:38.674","Text":"Quickly remind ourselves of these terms from our previous section."},{"Start":"01:38.674 ","End":"01:41.000","Text":"Hydrophilic, this describes ions are"},{"Start":"01:41.000 ","End":"01:44.330","Text":"polar molecules that attract well with other polar molecules such as water,"},{"Start":"01:44.330 ","End":"01:48.095","Text":"so salt or sugar interacts well, dissolves."},{"Start":"01:48.095 ","End":"01:50.240","Text":"Then you have hydrophobic."},{"Start":"01:50.240 ","End":"01:52.550","Text":"This describes uncharged non-polar molecules"},{"Start":"01:52.550 ","End":"01:54.680","Text":"that do not interact well with polar molecules such as water."},{"Start":"01:54.680 ","End":"01:59.680","Text":"And we gave the example of lipids, fat, oil."},{"Start":"01:59.680 ","End":"02:07.855","Text":"The polar hydrophilic region interacts favorably with water and tends to dissolve in it."},{"Start":"02:07.855 ","End":"02:15.405","Text":"The non-polar, the hydrophobic region tends to avoid contact with water,"},{"Start":"02:15.405 ","End":"02:20.200","Text":"so amphipathic, if we go back to that definition that we said,"},{"Start":"02:20.200 ","End":"02:25.390","Text":"it has both feelings with regards to water."},{"Start":"02:25.390 ","End":"02:33.955","Text":"It has both the philic and the phobic portions,"},{"Start":"02:33.955 ","End":"02:39.235","Text":"the polar and non-polar portions that like or dislike interacting with water."},{"Start":"02:39.235 ","End":"02:44.285","Text":"The non-polar hydrophobic region tends to avoid contact with water."},{"Start":"02:44.285 ","End":"02:48.620","Text":"The non-polar regions, therefore cluster together to"},{"Start":"02:48.620 ","End":"02:52.610","Text":"present the smallest hydrophobic area to the aqueous solvent,"},{"Start":"02:52.610 ","End":"02:54.695","Text":"to the water solvent."},{"Start":"02:54.695 ","End":"02:58.820","Text":"If they cluster together and form in a way"},{"Start":"02:58.820 ","End":"03:03.005","Text":"that they\u0027re centering and getting close to each other."},{"Start":"03:03.005 ","End":"03:07.355","Text":"Less of these hydrophobic non-polar regions"},{"Start":"03:07.355 ","End":"03:12.765","Text":"actually are exposed to polar water molecules."},{"Start":"03:12.765 ","End":"03:15.530","Text":"The polar regions therefore arrange as to"},{"Start":"03:15.530 ","End":"03:18.170","Text":"maximize their interaction with the solvent where"},{"Start":"03:18.170 ","End":"03:23.900","Text":"they are on the outside of this cluster and they are closest to the solvent,"},{"Start":"03:23.900 ","End":"03:26.165","Text":"to the polar molecules."},{"Start":"03:26.165 ","End":"03:29.435","Text":"In this case, we mentioned water."},{"Start":"03:29.435 ","End":"03:36.140","Text":"They maximize their interaction with the water based solvent."},{"Start":"03:36.140 ","End":"03:40.250","Text":"Whereas here, the nonpolar regions cluster together to"},{"Start":"03:40.250 ","End":"03:44.645","Text":"avoid as much as they can the aqueous water-based solvent."},{"Start":"03:44.645 ","End":"03:51.755","Text":"Now, this is a phenomena known as the hydrophobic effect."},{"Start":"03:51.755 ","End":"03:57.680","Text":"The hydrophobia of the aspects of the non-polar part"},{"Start":"03:57.680 ","End":"04:03.570","Text":"of the amphipathic molecule result in this effect."},{"Start":"04:03.570 ","End":"04:07.893","Text":"These stable structures called micelles or"},{"Start":"04:07.893 ","End":"04:13.160","Text":"micelles may contain hundreds or thousands of molecules."},{"Start":"04:13.160 ","End":"04:16.775","Text":"The forces that hold."},{"Start":"04:16.775 ","End":"04:26.850","Text":"This is the structure micelle and you see the hydrophilic heads,"},{"Start":"04:26.850 ","End":"04:28.580","Text":"if we talked about the phospholipid,"},{"Start":"04:28.580 ","End":"04:30.800","Text":"this is the hydrophilic head and you have"},{"Start":"04:30.800 ","End":"04:38.330","Text":"the hydrophobic tails or the hydrophobic portion of the amphipathic molecule that"},{"Start":"04:38.330 ","End":"04:44.600","Text":"is clustering together and forms this stable structure so that"},{"Start":"04:44.600 ","End":"04:47.510","Text":"the hydrophilic portion is the one that is"},{"Start":"04:47.510 ","End":"04:52.025","Text":"exposed to the aqueous, the water-based solvent."},{"Start":"04:52.025 ","End":"04:55.280","Text":"This terminology can be confusing because the strength of interaction is"},{"Start":"04:55.280 ","End":"04:58.790","Text":"not due to any intrinsic attraction between the non-polar regions."},{"Start":"04:58.790 ","End":"05:01.070","Text":"It\u0027s not because of attraction here,"},{"Start":"05:01.070 ","End":"05:02.960","Text":"rather it is the result from the systems achieving"},{"Start":"05:02.960 ","End":"05:05.810","Text":"the greatest thermodynamic stability by minimizing the number of"},{"Start":"05:05.810 ","End":"05:08.630","Text":"ordered water molecules required to surround and protect"},{"Start":"05:08.630 ","End":"05:13.020","Text":"the hydrophobic portions of the solute molecules from interacting with water molecules,"},{"Start":"05:13.020 ","End":"05:16.820","Text":"so they\u0027ve clustered together to then"},{"Start":"05:16.820 ","End":"05:21.485","Text":"just have the smallest amount of water that interacts with them."},{"Start":"05:21.485 ","End":"05:24.155","Text":"If we look at amphipathic compounds,"},{"Start":"05:24.155 ","End":"05:27.980","Text":"meaning they have the both feelings about water, love,"},{"Start":"05:27.980 ","End":"05:29.330","Text":"and hate in a way,"},{"Start":"05:29.330 ","End":"05:31.970","Text":"in aqueous solution, you have a hydrophilic head,"},{"Start":"05:31.970 ","End":"05:33.590","Text":"the one that interacts with water,"},{"Start":"05:33.590 ","End":"05:36.080","Text":"that loves water, and the hydrophobic tails,"},{"Start":"05:36.080 ","End":"05:40.400","Text":"the portion that\u0027s nonpolar versus the polar head that doesn\u0027t like interacting"},{"Start":"05:40.400 ","End":"05:44.960","Text":"with water so what you have is the water molecules around the hydrophobic tail."},{"Start":"05:44.960 ","End":"05:46.430","Text":"They are repelled,"},{"Start":"05:46.430 ","End":"05:48.650","Text":"the knot keeps this weird relationship where"},{"Start":"05:48.650 ","End":"05:51.320","Text":"water can\u0027t freely just interact with them and"},{"Start":"05:51.320 ","End":"05:56.614","Text":"therefore it\u0027s a little more ordered and to reduce this order as much as possible,"},{"Start":"05:56.614 ","End":"06:05.300","Text":"these portions will cluster together and then you have water around here that can just"},{"Start":"06:05.300 ","End":"06:09.740","Text":"randomly float around all these regions and not"},{"Start":"06:09.740 ","End":"06:14.390","Text":"have to get this repelling interaction in between."},{"Start":"06:14.390 ","End":"06:15.920","Text":"This is in essence,"},{"Start":"06:15.920 ","End":"06:21.230","Text":"the hydrophobic interaction that causes this hydrophobic effect,"},{"Start":"06:21.230 ","End":"06:25.109","Text":"being that this is this cage,"},{"Start":"06:25.109 ","End":"06:28.125","Text":"this cluster that forms."},{"Start":"06:28.125 ","End":"06:35.240","Text":"Now, many biomolecules are amphipathic: proteins, pigments,"},{"Start":"06:35.240 ","End":"06:38.875","Text":"some vitamins, phospholipids of membranes,"},{"Start":"06:38.875 ","End":"06:43.475","Text":"they all have both polar and non-polar surface regions."},{"Start":"06:43.475 ","End":"06:49.760","Text":"Structures composed of these molecules are stabilized by the hydrophobic effect,"},{"Start":"06:49.760 ","End":"06:51.590","Text":"which favors aggregation of"},{"Start":"06:51.590 ","End":"06:57.860","Text":"the non-polar hydrophobic water repelling regions either this way,"},{"Start":"06:57.860 ","End":"07:00.365","Text":"which is what we would see in a phospholipid bi-layer,"},{"Start":"07:00.365 ","End":"07:03.955","Text":"so it\u0027s a double-layer lipid."},{"Start":"07:03.955 ","End":"07:10.620","Text":"Here you have the single-layer lipid sphere the micelle or micelle."},{"Start":"07:10.620 ","End":"07:14.180","Text":"These are stabilized by this hydrophobic effect,"},{"Start":"07:14.180 ","End":"07:18.215","Text":"not by interaction and attraction of these,"},{"Start":"07:18.215 ","End":"07:26.285","Text":"but by having the repelling nature and the attraction of these portions to the water."},{"Start":"07:26.285 ","End":"07:30.575","Text":"Biological membranes are actually a result of"},{"Start":"07:30.575 ","End":"07:37.805","Text":"the hydrophobic effect or interaction among lipids and between lipids and proteins,"},{"Start":"07:37.805 ","End":"07:44.785","Text":"which is the most important determinant of structure in these membranes."},{"Start":"07:44.785 ","End":"07:52.190","Text":"If you see this is what results in the lipid bi-layer sheet in a membrane."},{"Start":"07:52.190 ","End":"07:55.985","Text":"Protein structure, the aggregation of"},{"Start":"07:55.985 ","End":"08:02.720","Text":"nonpolar amino acids in protein interiors in the inside of the protein,"},{"Start":"08:02.720 ","End":"08:10.190","Text":"driven by the hydrophobic effect stabilizes the 3-dimensional structure of the proteins."},{"Start":"08:10.190 ","End":"08:13.040","Text":"You have in proteins because we mentioned that"},{"Start":"08:13.040 ","End":"08:16.880","Text":"these are also biomolecules that can be amphipathic,"},{"Start":"08:16.880 ","End":"08:20.810","Text":"the region of the protein that is non-polar,"},{"Start":"08:20.810 ","End":"08:24.710","Text":"the amino acid side aggregate together driven by"},{"Start":"08:24.710 ","End":"08:29.560","Text":"this hydrophobic effect as in avoiding water molecules."},{"Start":"08:29.560 ","End":"08:36.120","Text":"Therefore, they fold and try to hide from the water."},{"Start":"08:36.120 ","End":"08:38.110","Text":"As you see here,"},{"Start":"08:38.110 ","End":"08:44.510","Text":"these hydrophobic interact with each other as trying to avoid all these water molecules,"},{"Start":"08:44.510 ","End":"08:49.985","Text":"this H_2O molecules and this stabilizes the 3-dimensional structures of"},{"Start":"08:49.985 ","End":"08:55.865","Text":"proteins where they\u0027re the non-polar amino acids clustered together,"},{"Start":"08:55.865 ","End":"08:58.310","Text":"allowing the polar regions,"},{"Start":"08:58.310 ","End":"09:02.645","Text":"polar amino acids to be what is exposed to the water."},{"Start":"09:02.645 ","End":"09:06.860","Text":"Hydrogen bonding between water and polar"},{"Start":"09:06.860 ","End":"09:11.330","Text":"solutes also causes an ordering of water molecules,"},{"Start":"09:11.330 ","End":"09:17.690","Text":"but the energetic effect is less significant than with non-polar solutes."},{"Start":"09:17.690 ","End":"09:20.990","Text":"Destruction of ordered water molecules as part of"},{"Start":"09:20.990 ","End":"09:24.485","Text":"the driving force for binding of a polar substrate,"},{"Start":"09:24.485 ","End":"09:30.860","Text":"a reactant to the complementary polar surface of an enzyme for example."},{"Start":"09:30.860 ","End":"09:38.455","Text":"Entropy increases as the enzyme displaces ordered water from the substrate."},{"Start":"09:38.455 ","End":"09:43.310","Text":"You have ordered water interacting with substrate and"},{"Start":"09:43.310 ","End":"09:49.760","Text":"the enzyme and as the enzyme displaces the ordered water from the substrate,"},{"Start":"09:49.760 ","End":"09:56.750","Text":"and as the substrate displaces ordered water from the enzyme surface, they interact."},{"Start":"09:56.750 ","End":"10:01.220","Text":"You see disordered water displaced by enzyme substrate interaction,"},{"Start":"10:01.220 ","End":"10:09.540","Text":"and the enzyme substrate interaction stabilizes by hydrogen bonding, ionic,"},{"Start":"10:09.540 ","End":"10:14.150","Text":"and hydrophobic interactions because the parts"},{"Start":"10:14.150 ","End":"10:16.340","Text":"that don\u0027t want to associate with water will"},{"Start":"10:16.340 ","End":"10:19.580","Text":"repel the water and associate with each other."},{"Start":"10:19.580 ","End":"10:25.910","Text":"You see here, hydrogen bonding between water and polar solutes,"},{"Start":"10:25.910 ","End":"10:28.850","Text":"also causing an ordering of water molecules,"},{"Start":"10:28.850 ","End":"10:34.505","Text":"yet the energetic effect is less significant than with non-polar solutes."},{"Start":"10:34.505 ","End":"10:37.820","Text":"Now with this, we completed the lesson of amphipathic compounds."},{"Start":"10:37.820 ","End":"10:41.375","Text":"By now you should be able to define an amphipathic compound,"},{"Start":"10:41.375 ","End":"10:44.045","Text":"explain the role and significance of such compounds,"},{"Start":"10:44.045 ","End":"10:47.630","Text":"and understand the hydrophobic effect."},{"Start":"10:47.630 ","End":"10:49.370","Text":"I give you homework,"},{"Start":"10:49.370 ","End":"10:53.375","Text":"say this word 3 times in a row if you can do it correctly."},{"Start":"10:53.375 ","End":"10:56.150","Text":"Amphipathic compound, amphipathic,"},{"Start":"10:56.150 ","End":"10:58.940","Text":"amphipathic, amphipathic practice it."},{"Start":"10:58.940 ","End":"11:01.560","Text":"Let\u0027s go into the exercises."}],"ID":28866},{"Watched":false,"Name":"Exercise 12","Duration":"1m 2s","ChapterTopicVideoID":27631,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.660","Text":"Welcome to exercises covering the lesson of amphipathic compounds."},{"Start":"00:03.660 ","End":"00:05.820","Text":"Hopefully by now, you can say this word."},{"Start":"00:05.820 ","End":"00:08.100","Text":"What are micelles?"},{"Start":"00:08.100 ","End":"00:12.820","Text":"Micelles are stable structures which can contain hundreds or thousands of molecules,"},{"Start":"00:12.820 ","End":"00:14.580","Text":"as you see many of them here,"},{"Start":"00:14.580 ","End":"00:16.965","Text":"that are held together by"},{"Start":"00:16.965 ","End":"00:22.245","Text":"the non-polar regions of the amphipathic molecules composing them."},{"Start":"00:22.245 ","End":"00:26.615","Text":"The forces that hold the non-polar regions of the molecules together"},{"Start":"00:26.615 ","End":"00:31.070","Text":"are sometimes referred to as hydrophobic interactions."},{"Start":"00:31.070 ","End":"00:35.675","Text":"It is an example of the phenomenon called the hydrophobic effect,"},{"Start":"00:35.675 ","End":"00:41.180","Text":"where the non-polar regions of the amphipathic molecules cluster together to present"},{"Start":"00:41.180 ","End":"00:47.930","Text":"the smallest hydrophobic area to the aqueous water-based solvent."},{"Start":"00:47.930 ","End":"00:51.320","Text":"While the polar regions arrange as to maximize"},{"Start":"00:51.320 ","End":"00:55.235","Text":"their interaction with the water-based solvent."},{"Start":"00:55.235 ","End":"01:03.480","Text":"What we see a micelle is a single layer lipid sphere. Here you see it."}],"ID":28867},{"Watched":false,"Name":"Exercise 13","Duration":"1m 6s","ChapterTopicVideoID":27632,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.164","Text":"Welcome back to Amphipathic Compounds."},{"Start":"00:03.164 ","End":"00:06.575","Text":"We are practicing and testing our knowledge."},{"Start":"00:06.575 ","End":"00:09.280","Text":"Explain the phenomena called the hydrophobic effect."},{"Start":"00:09.280 ","End":"00:12.899","Text":"When considering an amphipathic compound in aqueous solution,"},{"Start":"00:12.899 ","End":"00:19.135","Text":"the polar hydrophilic region interact favorably with water and tends to dissolve."},{"Start":"00:19.135 ","End":"00:24.390","Text":"The non-polar, the hydrophobic region tends to avoid contact with water."},{"Start":"00:24.390 ","End":"00:27.780","Text":"The non-polar regions clustered together to present"},{"Start":"00:27.780 ","End":"00:31.920","Text":"the smallest hydrophobic area to the aqueous"},{"Start":"00:31.920 ","End":"00:35.870","Text":"water-based solvent and the polar regions range"},{"Start":"00:35.870 ","End":"00:40.070","Text":"as to maximize their interaction with the water-based solvent."},{"Start":"00:40.070 ","End":"00:45.095","Text":"Now, the driving force here as mentioned is the actual repelling"},{"Start":"00:45.095 ","End":"00:50.660","Text":"or desire to avoid the surface,"},{"Start":"00:50.660 ","End":"00:54.110","Text":"the interaction between the polar water molecules,"},{"Start":"00:54.110 ","End":"01:00.665","Text":"the polar solvent and the non-polar regions, the hydrophobic areas."},{"Start":"01:00.665 ","End":"01:04.294","Text":"That is what creates this arrangement."},{"Start":"01:04.294 ","End":"01:07.200","Text":"There we have it. Let\u0027s move on."}],"ID":28868},{"Watched":false,"Name":"Exercise 14","Duration":"1m 14s","ChapterTopicVideoID":27633,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.090","Text":"Welcome to an exercise covering the lesson of Amphipathic Compounds."},{"Start":"00:06.090 ","End":"00:10.200","Text":"Define an amphipathic compound and give an example of 1."},{"Start":"00:10.200 ","End":"00:14.190","Text":"Amphipathic molecules are chemical compounds that contain"},{"Start":"00:14.190 ","End":"00:18.615","Text":"both polar or charged and nonpolar,"},{"Start":"00:18.615 ","End":"00:23.505","Text":"apolar, regions or portions in their structure."},{"Start":"00:23.505 ","End":"00:27.180","Text":"This means that it is a chemical compound that has"},{"Start":"00:27.180 ","End":"00:32.850","Text":"both a polar and non-polar region or portion in the same structure."},{"Start":"00:32.850 ","End":"00:37.140","Text":"The term amphipathic came from Greek with Amphis meaning both,"},{"Start":"00:37.140 ","End":"00:39.900","Text":"and Patheia meaning suffering or feeling."},{"Start":"00:39.900 ","End":"00:43.940","Text":"The idea is that they have both feelings,"},{"Start":"00:43.940 ","End":"00:50.510","Text":"love and fear, or hate of water or of polar molecules."},{"Start":"00:50.510 ","End":"00:53.660","Text":"Examples that we mentioned are phospholipids."},{"Start":"00:53.660 ","End":"00:56.375","Text":"As we know, this results in the bi-layer."},{"Start":"00:56.375 ","End":"00:59.440","Text":"Proteins, we mentioned this as well."},{"Start":"00:59.440 ","End":"01:04.220","Text":"We refer to the 3D structure of these being affected by"},{"Start":"01:04.220 ","End":"01:07.985","Text":"these polar and non-polar regions and"},{"Start":"01:07.985 ","End":"01:14.700","Text":"some vitamins and additional many more biomolecules. Let\u0027s move on."}],"ID":28869},{"Watched":false,"Name":"Exercise 15","Duration":"1m 42s","ChapterTopicVideoID":27634,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.420","Text":"Welcome back to an additional question"},{"Start":"00:03.420 ","End":"00:08.369","Text":"covering what we learned in the Amphipathic Compounds lesson."},{"Start":"00:08.369 ","End":"00:10.680","Text":"Many biomolecules are amphipathic,"},{"Start":"00:10.680 ","End":"00:13.140","Text":"give an example of how this dual characteristic plays"},{"Start":"00:13.140 ","End":"00:15.990","Text":"an important role in a cell in an organism."},{"Start":"00:15.990 ","End":"00:17.850","Text":"Biomolecules such as proteins,"},{"Start":"00:17.850 ","End":"00:19.470","Text":"pigments, some vitamins, sterols,"},{"Start":"00:19.470 ","End":"00:21.540","Text":"and phospholipids of membranes all have"},{"Start":"00:21.540 ","End":"00:24.225","Text":"both polar and nonpolar surface regions"},{"Start":"00:24.225 ","End":"00:27.590","Text":"and this contributes in not just to remind you that structure,"},{"Start":"00:27.590 ","End":"00:34.485","Text":"this dual characteristic is what actually defines it as an amphipathic molecule."},{"Start":"00:34.485 ","End":"00:36.830","Text":"This contributes in that structure is composed of"},{"Start":"00:36.830 ","End":"00:39.560","Text":"these molecules are stabilized by the hydrophobic effect,"},{"Start":"00:39.560 ","End":"00:44.000","Text":"which favors aggregation of the nonpolar hydrophobic water repelling"},{"Start":"00:44.000 ","End":"00:49.415","Text":"regions and these play important roles like micelles are an example of such a structure."},{"Start":"00:49.415 ","End":"00:53.030","Text":"They play a role in stabilizing structures."},{"Start":"00:53.030 ","End":"00:56.960","Text":"Biological membranes are dependent on these characteristics."},{"Start":"00:56.960 ","End":"00:58.430","Text":"When we say the hydrophobic effect,"},{"Start":"00:58.430 ","End":"01:02.140","Text":"we mean the interaction among lipids and between lipids."},{"Start":"01:02.140 ","End":"01:06.710","Text":"The hydrophobic effect or interaction among lipids and between lipids and"},{"Start":"01:06.710 ","End":"01:11.885","Text":"proteins is the most important determinant of structure in these membranes,"},{"Start":"01:11.885 ","End":"01:15.320","Text":"protein structure is affected by this in that"},{"Start":"01:15.320 ","End":"01:19.730","Text":"the aggregation of nonpolar amino acid and protein interiors,"},{"Start":"01:19.730 ","End":"01:24.530","Text":"driven by the hydrophobic effect stabilizes the three-dimensional structures of"},{"Start":"01:24.530 ","End":"01:29.870","Text":"proteins so when thinking of protein-protein interactions of an enzyme and its substrate,"},{"Start":"01:29.870 ","End":"01:34.790","Text":"the structure is crucial and these aggregations of"},{"Start":"01:34.790 ","End":"01:42.960","Text":"the nonpolar amino acids is what stabilizes the 3D structure of the proteins."}],"ID":28870},{"Watched":false,"Name":"Van Der Waals Interactions","Duration":"4m 22s","ChapterTopicVideoID":27638,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.550","Text":"Hi, there. In this lesson,"},{"Start":"00:02.550 ","End":"00:07.110","Text":"we will talk about van der Waals interactions as part of the topic"},{"Start":"00:07.110 ","End":"00:11.780","Text":"of weak noncovalent interactions in the chapter dealing with water."},{"Start":"00:11.780 ","End":"00:13.110","Text":"By the end of this session,"},{"Start":"00:13.110 ","End":"00:14.879","Text":"you will be able to define"},{"Start":"00:14.879 ","End":"00:18.030","Text":"van der Waals interactions and describe the van der Waals radius."},{"Start":"00:18.030 ","End":"00:19.830","Text":"Now van der Waals interactions,"},{"Start":"00:19.830 ","End":"00:22.440","Text":"these are weak intermolecular forces between"},{"Start":"00:22.440 ","End":"00:26.865","Text":"molecules as a result of each inducing polarization in the other."},{"Start":"00:26.865 ","End":"00:29.850","Text":"In other words, van der Waals forces are driven by"},{"Start":"00:29.850 ","End":"00:32.580","Text":"induced electrical interactions between"},{"Start":"00:32.580 ","End":"00:36.660","Text":"two or more atoms or molecules that are very close to each other."},{"Start":"00:36.660 ","End":"00:43.010","Text":"Again, these are weak intermolecular forces between molecules that are"},{"Start":"00:43.010 ","End":"00:52.025","Text":"an interaction that results from a polarization that is induced one in the other."},{"Start":"00:52.025 ","End":"00:56.539","Text":"They are driven by an induced electrical interaction"},{"Start":"00:56.539 ","End":"01:01.495","Text":"between two or more atoms or molecules that are close to each other."},{"Start":"01:01.495 ","End":"01:05.870","Text":"When two uncharged atoms are very close to each other,"},{"Start":"01:05.870 ","End":"01:09.440","Text":"their electron cloud influences each other."},{"Start":"01:09.440 ","End":"01:14.449","Text":"Random variations in the positions of electrons around one nucleus"},{"Start":"01:14.449 ","End":"01:18.965","Text":"may create a transient electric dipole in one atom,"},{"Start":"01:18.965 ","End":"01:25.840","Text":"which induces a transient opposite electric dipole in the nearby atom."},{"Start":"01:25.840 ","End":"01:29.855","Text":"The two dipoles weakly attract each other,"},{"Start":"01:29.855 ","End":"01:31.558","Text":"bringing the nuclei closer,"},{"Start":"01:31.558 ","End":"01:36.860","Text":"and these weak attractions are called van der Waals interactions."},{"Start":"01:36.860 ","End":"01:40.835","Text":"These are also known as London forces,"},{"Start":"01:40.835 ","End":"01:42.925","Text":"a term that\u0027s rarely used."},{"Start":"01:42.925 ","End":"01:45.755","Text":"Now as the two nuclei draw closer together,"},{"Start":"01:45.755 ","End":"01:49.040","Text":"their electron clouds begin to repel each other."},{"Start":"01:49.040 ","End":"01:52.010","Text":"At the point where the net attraction is maximal,"},{"Start":"01:52.010 ","End":"01:56.195","Text":"the nuclei are said to be in van der Waals contact."},{"Start":"01:56.195 ","End":"02:00.109","Text":"Van der Waals contact is that point where the net attraction"},{"Start":"02:00.109 ","End":"02:03.885","Text":"between the two nuclei is maximal."},{"Start":"02:03.885 ","End":"02:08.884","Text":"Each atom has a characteristic van der Waals radius,"},{"Start":"02:08.884 ","End":"02:14.215","Text":"which is a measure of how close the atom will allow another to approach."},{"Start":"02:14.215 ","End":"02:18.225","Text":"If we look here in this table,"},{"Start":"02:18.225 ","End":"02:19.710","Text":"you see for hydrogen,"},{"Start":"02:19.710 ","End":"02:23.750","Text":"the van der Waals radius nanometers is 0.11."},{"Start":"02:23.750 ","End":"02:25.310","Text":"For oxygen 0.15,"},{"Start":"02:25.310 ","End":"02:26.600","Text":"nitrogen is the same as oxygen,"},{"Start":"02:26.600 ","End":"02:29.780","Text":"0.15, and carbon, 0.17."},{"Start":"02:29.780 ","End":"02:32.644","Text":"Covalent radius for single bond,"},{"Start":"02:32.644 ","End":"02:38.855","Text":"you see this is smaller because covalent bonds are stronger."},{"Start":"02:38.855 ","End":"02:40.940","Text":"The minute it\u0027s stronger, we talked about this in a previous section,"},{"Start":"02:40.940 ","End":"02:42.680","Text":"it means that it\u0027s closer to each other."},{"Start":"02:42.680 ","End":"02:46.580","Text":"So this refers to the nanometers,"},{"Start":"02:46.580 ","End":"02:51.155","Text":"the distance, the radius of each element,"},{"Start":"02:51.155 ","End":"02:56.960","Text":"how close that atom will allow another one to get to it,"},{"Start":"02:56.960 ","End":"03:00.605","Text":"to approach it without having a covalent bond."},{"Start":"03:00.605 ","End":"03:06.200","Text":"This is as close as hydrogen will allow another atom to"},{"Start":"03:06.200 ","End":"03:12.140","Text":"get close to it and have this weak non-covalent interaction,"},{"Start":"03:12.140 ","End":"03:14.270","Text":"this van der Waals interactions,"},{"Start":"03:14.270 ","End":"03:15.649","Text":"this van der Waals contact,"},{"Start":"03:15.649 ","End":"03:20.310","Text":"and it\u0027s defined by the van der Waals radius."},{"Start":"03:20.310 ","End":"03:23.495","Text":"The van der Waals interaction is the weakest of"},{"Start":"03:23.495 ","End":"03:27.215","Text":"all intermolecular attractions between molecules."},{"Start":"03:27.215 ","End":"03:30.185","Text":"To explain this further in molecular physics,"},{"Start":"03:30.185 ","End":"03:32.014","Text":"the van der Waals force,"},{"Start":"03:32.014 ","End":"03:36.665","Text":"named after Dutch physicist Johannes Diderik van der Waals,"},{"Start":"03:36.665 ","End":"03:42.565","Text":"is a distance dependent interaction between atoms or molecules."},{"Start":"03:42.565 ","End":"03:45.200","Text":"Unlike ionic or covalent bonds,"},{"Start":"03:45.200 ","End":"03:48.650","Text":"these attractions did not result from a chemical electronic bond,"},{"Start":"03:48.650 ","End":"03:53.420","Text":"they are comparatively weak and therefore more susceptible to disturbance."},{"Start":"03:53.420 ","End":"03:58.130","Text":"The van der Waals force quickly disappears, in other words,"},{"Start":"03:58.130 ","End":"04:03.380","Text":"seizes to exist at longer distances between interacting molecules."},{"Start":"04:03.380 ","End":"04:10.295","Text":"Again, it\u0027s dependent on this proximity between these interacting molecules."},{"Start":"04:10.295 ","End":"04:15.125","Text":"With that, we have covered van der Waals interactions."},{"Start":"04:15.125 ","End":"04:18.724","Text":"We described the van der Waals radius and even van der Waals contact."},{"Start":"04:18.724 ","End":"04:23.490","Text":"Let\u0027s test the knowledge in our exercises."}],"ID":28871},{"Watched":false,"Name":"Exercise 16","Duration":"43s","ChapterTopicVideoID":27635,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.840","Text":"Hello, we are covering an exercise in the topic of Van der Waals interactions."},{"Start":"00:06.840 ","End":"00:11.715","Text":"Define Van der Waals interactions and what is another term for these?"},{"Start":"00:11.715 ","End":"00:17.145","Text":"Okay, so Van der Waals interactions are weak intermolecular forces between molecules,"},{"Start":"00:17.145 ","End":"00:22.290","Text":"which is the result of each molecule inducing polarization in the other."},{"Start":"00:22.290 ","End":"00:28.530","Text":"In other words, these are weak short range electrostatic attractive forces between"},{"Start":"00:28.530 ","End":"00:36.885","Text":"uncharged molecules arising from the interaction of transient electric dipole moments."},{"Start":"00:36.885 ","End":"00:39.150","Text":"These are also known as London forces,"},{"Start":"00:39.150 ","End":"00:41.955","Text":"though this is a term that is rarely used."},{"Start":"00:41.955 ","End":"00:44.170","Text":"Let\u0027s move forward."}],"ID":28872},{"Watched":false,"Name":"Exercise 17","Duration":"2m 53s","ChapterTopicVideoID":27636,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.200","Text":"Welcome back to an exercise covering Van der Waals Interactions."},{"Start":"00:04.200 ","End":"00:06.900","Text":"Which of the following is true about van der Waals interactions?"},{"Start":"00:06.900 ","End":"00:09.840","Text":"A, when 2 uncharged atoms are very close to each other,"},{"Start":"00:09.840 ","End":"00:11.965","Text":"their electron clouds influence each other."},{"Start":"00:11.965 ","End":"00:15.750","Text":"B, random variations in the positions of the electrons around"},{"Start":"00:15.750 ","End":"00:19.515","Text":"1 nucleus can create a transient electric dipole in 1 atom,"},{"Start":"00:19.515 ","End":"00:23.459","Text":"which induces a transient opposite electric dipole in the nearby atom."},{"Start":"00:23.459 ","End":"00:26.700","Text":"C, the 2 dipoles weakly attract each other,"},{"Start":"00:26.700 ","End":"00:27.950","Text":"bringing the nuclei closer,"},{"Start":"00:27.950 ","End":"00:31.440","Text":"and these weak attractions are van der Waals interactions."},{"Start":"00:31.440 ","End":"00:35.190","Text":"D, each atom has a characteristic van der Waals radius,"},{"Start":"00:35.190 ","End":"00:38.880","Text":"which is a measure of how close that atom will allow another to approach."},{"Start":"00:38.880 ","End":"00:40.695","Text":"E, all of the above."},{"Start":"00:40.695 ","End":"00:44.580","Text":"A, went 2 uncharged atoms are very close to each other,"},{"Start":"00:44.580 ","End":"00:46.565","Text":"their electron clouds influence each other."},{"Start":"00:46.565 ","End":"00:49.145","Text":"Well, in van der Waals interactions,"},{"Start":"00:49.145 ","End":"00:52.340","Text":"we mentioned that these are the weakest and it\u0027s because it\u0027s actually between"},{"Start":"00:52.340 ","End":"00:56.900","Text":"2 uncharged atoms and that when they are close enough to each other,"},{"Start":"00:56.900 ","End":"01:00.440","Text":"the electron orbitals, these clouds that are created"},{"Start":"01:00.440 ","End":"01:04.205","Text":"from these electrons that are orbiting around influence each other,"},{"Start":"01:04.205 ","End":"01:06.965","Text":"so that we know is true."},{"Start":"01:06.965 ","End":"01:09.200","Text":"Let\u0027s check the other ones and verify."},{"Start":"01:09.200 ","End":"01:13.010","Text":"B, random variations in the positions of the electrons around"},{"Start":"01:13.010 ","End":"01:17.135","Text":"1 nucleus can create a transient electric dipole in 1 atom,"},{"Start":"01:17.135 ","End":"01:22.685","Text":"which then induces a transient opposite electric dipole and the nearby atom."},{"Start":"01:22.685 ","End":"01:28.550","Text":"Well, we actually define van der Waals interactions by this sentence,"},{"Start":"01:28.550 ","End":"01:31.550","Text":"so this seems to be true as well."},{"Start":"01:31.550 ","End":"01:34.625","Text":"Let\u0027s move forward and see if we find other ones."},{"Start":"01:34.625 ","End":"01:38.465","Text":"C, the 2 dipoles weakly attract each other,"},{"Start":"01:38.465 ","End":"01:40.460","Text":"bringing the nuclei closer."},{"Start":"01:40.460 ","End":"01:42.950","Text":"These transient electric dipoles in this"},{"Start":"01:42.950 ","End":"01:49.700","Text":"electron cloud results in this weak attraction that brings the nuclei closer,"},{"Start":"01:49.700 ","End":"01:53.870","Text":"and these weak attractions are van der Waals interaction,"},{"Start":"01:53.870 ","End":"01:57.200","Text":"so this also seems true."},{"Start":"01:57.200 ","End":"02:00.105","Text":"D, before we can say all the above,"},{"Start":"02:00.105 ","End":"02:04.055","Text":"we still want to verify because if we find 1 that\u0027s untrue,"},{"Start":"02:04.055 ","End":"02:10.760","Text":"then it makes us question everything and see which one is the most correctly described."},{"Start":"02:10.760 ","End":"02:14.930","Text":"So d, each atom has a characteristic van der Waals radius,"},{"Start":"02:14.930 ","End":"02:19.025","Text":"which is a measure of how close the atom will allow another to approach."},{"Start":"02:19.025 ","End":"02:23.000","Text":"Yes, we actually talked about this and showed a table"},{"Start":"02:23.000 ","End":"02:28.160","Text":"where we saw the van der Waals radius for nitrogen and oxygen."},{"Start":"02:28.160 ","End":"02:32.780","Text":"Meaning that what is the proximity of"},{"Start":"02:32.780 ","End":"02:38.150","Text":"which 2 atoms in a Van der Waals interaction can associate and get close to,"},{"Start":"02:38.150 ","End":"02:39.710","Text":"so this is true as well,"},{"Start":"02:39.710 ","End":"02:44.265","Text":"and that means e sounds right, so it\u0027s not a,"},{"Start":"02:44.265 ","End":"02:47.130","Text":"it\u0027s not b, it\u0027s not c or d,"},{"Start":"02:47.130 ","End":"02:50.600","Text":"rather it is e because all of the above are true."},{"Start":"02:50.600 ","End":"02:53.970","Text":"Thanks, let\u0027s move to another exercise."}],"ID":28873},{"Watched":false,"Name":"Exercise 18","Duration":"1m 2s","ChapterTopicVideoID":27637,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.840","Text":"Hey, there. We are in the topic of"},{"Start":"00:03.840 ","End":"00:09.720","Text":"weak interactions in the section covering van der Waals Interactions."},{"Start":"00:09.720 ","End":"00:11.685","Text":"Let\u0027s dive into a question."},{"Start":"00:11.685 ","End":"00:14.850","Text":"Explain the term van der Waals contact."},{"Start":"00:14.850 ","End":"00:17.430","Text":"When 2 uncharged atoms are very close to each"},{"Start":"00:17.430 ","End":"00:19.950","Text":"other and their electron clouds influence each other"},{"Start":"00:19.950 ","End":"00:25.080","Text":"to create transient electric dipoles in each of the 2 interacting atoms,"},{"Start":"00:25.080 ","End":"00:28.340","Text":"these 2 that are in the van der Waals interaction,"},{"Start":"00:28.340 ","End":"00:31.265","Text":"the 2 dipoles weakly attract each other,"},{"Start":"00:31.265 ","End":"00:33.890","Text":"bringing the nuclei closer."},{"Start":"00:33.890 ","End":"00:38.700","Text":"This point when the 2 nuclei of"},{"Start":"00:38.700 ","End":"00:41.495","Text":"the 2 molecules draw closer together"},{"Start":"00:41.495 ","End":"00:44.810","Text":"and their electron clouds begin to repel each other,"},{"Start":"00:44.810 ","End":"00:46.460","Text":"and at that point,"},{"Start":"00:46.460 ","End":"00:50.457","Text":"where the net attraction is maximal between the 2 nuclei,"},{"Start":"00:50.457 ","End":"00:54.905","Text":"the nuclei are said to be in van der Waals contact."},{"Start":"00:54.905 ","End":"00:57.560","Text":"With that, we completed this exercise within"},{"Start":"00:57.560 ","End":"01:02.760","Text":"the lesson covering our knowledge on van der Waals Interactions."}],"ID":28874},{"Watched":false,"Name":"Weak Interactions Crucial Role in Life","Duration":"10m 45s","ChapterTopicVideoID":27639,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.420","Text":"Hi. Now that we\u0027ve covered"},{"Start":"00:03.420 ","End":"00:08.085","Text":"a few sections within the topic of weak non-covalent interactions,"},{"Start":"00:08.085 ","End":"00:11.940","Text":"how are these chemical interactions,"},{"Start":"00:11.940 ","End":"00:15.690","Text":"these weak interactions, crucial to life?"},{"Start":"00:15.690 ","End":"00:19.320","Text":"What is the weak interactions\u0027 crucial role in life?"},{"Start":"00:19.320 ","End":"00:23.775","Text":"By the end of this section, you will be able to list the 4 types of non-covalent bonds,"},{"Start":"00:23.775 ","End":"00:25.800","Text":"describe the underlying force of these bonds,"},{"Start":"00:25.800 ","End":"00:29.085","Text":"and understand their significance to biology."},{"Start":"00:29.085 ","End":"00:33.164","Text":"We covered 4 types of non-covalent bonds."},{"Start":"00:33.164 ","End":"00:35.550","Text":"We started with hydrogen bonds,"},{"Start":"00:35.550 ","End":"00:37.665","Text":"and we talked about the ionic bonds,"},{"Start":"00:37.665 ","End":"00:42.585","Text":"the hydrophobic bonds and finally,"},{"Start":"00:42.585 ","End":"00:45.685","Text":"the weak van der Waals bonds."},{"Start":"00:45.685 ","End":"00:50.960","Text":"Now these are all individually weaker than covalent bonds,"},{"Start":"00:50.960 ","End":"00:55.655","Text":"yet the cumulative effect of any such interactions can be very significant."},{"Start":"00:55.655 ","End":"00:59.195","Text":"The formation of each of these weak bonds"},{"Start":"00:59.195 ","End":"01:03.680","Text":"contributes to a net decrease in the free energy of the system."},{"Start":"01:03.680 ","End":"01:09.860","Text":"We can calculate the stability of a non-covalent interaction from the binding energy,"},{"Start":"01:09.860 ","End":"01:14.525","Text":"the reduction in the energy of the system when binding occurs."},{"Start":"01:14.525 ","End":"01:21.575","Text":"To dissociate 2 biomolecules non-covalently associated,"},{"Start":"01:21.575 ","End":"01:27.445","Text":"such as an enzyme and it\u0027s balanced substrate through multiple weak interactions,"},{"Start":"01:27.445 ","End":"01:33.290","Text":"all these interactions must be disrupted at the same time."},{"Start":"01:33.290 ","End":"01:36.559","Text":"Because these interactions are constantly fluctuating randomly,"},{"Start":"01:36.559 ","End":"01:39.920","Text":"such simultaneous disruptions are very unlikely."},{"Start":"01:39.920 ","End":"01:45.275","Text":"Therefore, 5 or 20 weak interactions be still much greater molecular stability"},{"Start":"01:45.275 ","End":"01:51.249","Text":"than would be expected intuitively from a simple summation of small binding energies."},{"Start":"01:51.249 ","End":"01:54.140","Text":"To repeat, to dissociate 2 biomolecules"},{"Start":"01:54.140 ","End":"01:58.190","Text":"non-covalently associated through multiple weak interactions,"},{"Start":"01:58.190 ","End":"02:05.010","Text":"all of these interactions must be disrupted in the same time."},{"Start":"02:05.010 ","End":"02:10.055","Text":"That means that because these interactions are constantly fluctuating randomly,"},{"Start":"02:10.055 ","End":"02:17.180","Text":"that for all of them to disrupt at the same time, is very unlikely."},{"Start":"02:17.180 ","End":"02:21.620","Text":"Therefore, these multiple weak interactions have"},{"Start":"02:21.620 ","End":"02:28.340","Text":"a cumulative effect of being very significant in the strength."},{"Start":"02:28.340 ","End":"02:32.083","Text":"Now, macromolecules, such as proteins, DNA,"},{"Start":"02:32.083 ","End":"02:36.875","Text":"and RNA, contain so many sites of non-covalent bonding,"},{"Start":"02:36.875 ","End":"02:39.200","Text":"hydrogen bonding, ionic, hydrophobic,"},{"Start":"02:39.200 ","End":"02:41.390","Text":"and van der Waals interactions that"},{"Start":"02:41.390 ","End":"02:46.435","Text":"the cumulative effect of the many small binding forces can be vast."},{"Start":"02:46.435 ","End":"02:51.470","Text":"Example, the non-covalent bonding of an enzyme to"},{"Start":"02:51.470 ","End":"02:58.775","Text":"its substrate may involve several hydrogen bonds and 1 or more ionic interactions,"},{"Start":"02:58.775 ","End":"03:03.290","Text":"as well as hydrophobic and van der Waals interactions."},{"Start":"03:03.290 ","End":"03:08.120","Text":"Here we see a figure showing the enzyme and the substrate."},{"Start":"03:08.120 ","End":"03:10.475","Text":"In order for this to bind,"},{"Start":"03:10.475 ","End":"03:14.810","Text":"it involves a few interactions."},{"Start":"03:14.810 ","End":"03:21.769","Text":"Here we see there are a few hydrogen bonds and they are depicted by these blue lines."},{"Start":"03:21.769 ","End":"03:24.830","Text":"For macromolecules, the most stable,"},{"Start":"03:24.830 ","End":"03:26.569","Text":"meaning the native structure,"},{"Start":"03:26.569 ","End":"03:30.530","Text":"is usually that in which weak interactions are maximized."},{"Start":"03:30.530 ","End":"03:34.400","Text":"For example, the folding of a single polypeptide or polynucleotide"},{"Start":"03:34.400 ","End":"03:38.705","Text":"chain into its 3-dimensional shape is determined by this principle;"},{"Start":"03:38.705 ","End":"03:42.920","Text":"the binding of an antigen to a specific antibody depends on"},{"Start":"03:42.920 ","End":"03:48.275","Text":"a cumulative effect or the cumulative effects of many weak interactions."},{"Start":"03:48.275 ","End":"03:52.040","Text":"As mentioned previously, the energy released when an enzyme binds"},{"Start":"03:52.040 ","End":"03:56.300","Text":"non-covalently to its substrate is the main source of the enzyme\u0027s catalytic power."},{"Start":"03:56.300 ","End":"04:00.020","Text":"The binding of a hormone or a neurotransmitter to"},{"Start":"04:00.020 ","End":"04:04.060","Text":"its cellular receptor protein is the result of multiple weak interactions."},{"Start":"04:04.060 ","End":"04:06.950","Text":"1 consequence of the large size of enzymes and"},{"Start":"04:06.950 ","End":"04:11.060","Text":"receptors relative to their substrates or ligands,"},{"Start":"04:11.060 ","End":"04:17.765","Text":"is that their extensive surface provides many opportunities for weak interactions."},{"Start":"04:17.765 ","End":"04:20.554","Text":"If we\u0027re looking at this and the big substrate,"},{"Start":"04:20.554 ","End":"04:22.880","Text":"it allows for many interactions because there\u0027s"},{"Start":"04:22.880 ","End":"04:25.640","Text":"space for many of the molecules to be present."},{"Start":"04:25.640 ","End":"04:29.270","Text":"As a reminder, many biomolecules are amphipathic and"},{"Start":"04:29.270 ","End":"04:33.755","Text":"the structures composed of these molecules are stabilized by the hydrophobic effect."},{"Start":"04:33.755 ","End":"04:38.450","Text":"Disruption of ordered water molecules is part of the driving force for binding of"},{"Start":"04:38.450 ","End":"04:43.850","Text":"a polar substrate or reactant to the complimentary polar surface of an enzyme."},{"Start":"04:43.850 ","End":"04:45.680","Text":"At the molecular level,"},{"Start":"04:45.680 ","End":"04:52.130","Text":"the complementarity between interacting biomolecules reflects the weak interactions"},{"Start":"04:52.130 ","End":"04:54.950","Text":"between polar and charged groups and"},{"Start":"04:54.950 ","End":"04:59.390","Text":"the proximity of hydrophobic patches on the surfaces of the molecules."},{"Start":"04:59.390 ","End":"05:06.035","Text":"For many proteins, the tightly bound water molecules are essential for their function."},{"Start":"05:06.035 ","End":"05:08.750","Text":"When the structure of a protein such as hemoglobin is"},{"Start":"05:08.750 ","End":"05:11.075","Text":"determined by x-ray crystallography,"},{"Start":"05:11.075 ","End":"05:13.130","Text":"water molecules are often found to be bound"},{"Start":"05:13.130 ","End":"05:15.785","Text":"so tightly that they are part of the crystal structure."},{"Start":"05:15.785 ","End":"05:19.670","Text":"The same occurs for water and crystals of RNA or DNA."},{"Start":"05:19.670 ","End":"05:24.290","Text":"Summarizing what we covered about weak interactions and their crucial role in life."},{"Start":"05:24.290 ","End":"05:26.480","Text":"Considering the prints of understanding"},{"Start":"05:26.480 ","End":"05:29.060","Text":"the concepts covered in these sections of these topics,"},{"Start":"05:29.060 ","End":"05:31.175","Text":"I will go over some key points again."},{"Start":"05:31.175 ","End":"05:37.865","Text":"Non-covalent bonds determine the shape of many large biomolecules"},{"Start":"05:37.865 ","End":"05:44.990","Text":"and stabilized complexes composed of 2 or more different molecules."},{"Start":"05:44.990 ","End":"05:50.780","Text":"There are 4 main types of non-covalent bonds in biological systems."},{"Start":"05:50.780 ","End":"05:54.845","Text":"We have hydrogen bonds, ionic bonds,"},{"Start":"05:54.845 ","End":"05:58.699","Text":"Van der Waals interactions, and hydrophobic bonds."},{"Start":"05:58.699 ","End":"06:05.600","Text":"Now the bond energies for these interactions range from about 1-5 kilo calories per mole."},{"Start":"06:05.600 ","End":"06:10.980","Text":"1-5 kilo calories per mole means 1,000-5,000 calories, that\u0027s what kilo means,"},{"Start":"06:10.980 ","End":"06:15.620","Text":"per 6.02 times 10^23rd molecules,"},{"Start":"06:15.620 ","End":"06:18.290","Text":"that is a mole Avogadro\u0027s number."},{"Start":"06:18.290 ","End":"06:20.210","Text":"In a hydrogen bond,"},{"Start":"06:20.210 ","End":"06:25.865","Text":"a hydrogen atom covalently bonded to an electronegative donor atom such as oxygen,"},{"Start":"06:25.865 ","End":"06:28.775","Text":"associates with an acceptor atom,"},{"Start":"06:28.775 ","End":"06:33.649","Text":"the oxygen, whose non-bonding electrons attract the hydrogen."},{"Start":"06:33.649 ","End":"06:37.880","Text":"Hydrogen bonds among water molecules are largely responsible for"},{"Start":"06:37.880 ","End":"06:43.225","Text":"the properties of both liquid water and the crystalline solid form, ice."},{"Start":"06:43.225 ","End":"06:45.560","Text":"Now, ionic bonds result from"},{"Start":"06:45.560 ","End":"06:50.330","Text":"the electrostatic attraction between the positive and negative charges of ions."},{"Start":"06:50.330 ","End":"06:54.920","Text":"In aqueous solutions, all cations and anions are"},{"Start":"06:54.920 ","End":"07:00.020","Text":"surrounded by a tightly bound shell of water molecules,"},{"Start":"07:00.020 ","End":"07:02.005","Text":"a cage like form."},{"Start":"07:02.005 ","End":"07:07.025","Text":"The weak and relatively non-specific van der Waals interactions are created"},{"Start":"07:07.025 ","End":"07:10.400","Text":"wherever any 2 atoms approach each other"},{"Start":"07:10.400 ","End":"07:14.675","Text":"closely and are in close proximity to each other,."},{"Start":"07:14.675 ","End":"07:20.525","Text":"They result from the attraction between transient dipoles associated with all molecules."},{"Start":"07:20.525 ","End":"07:24.535","Text":"Hydrophobic bonds occur between non-polar molecules,"},{"Start":"07:24.535 ","End":"07:26.629","Text":"such as hydrocarbons,"},{"Start":"07:26.629 ","End":"07:28.955","Text":"in an aqueous environment."},{"Start":"07:28.955 ","End":"07:34.910","Text":"These hydrophobic bonds result mainly because aggregation of"},{"Start":"07:34.910 ","End":"07:41.915","Text":"the hydrophobic molecules necessitates less organization of water into cages."},{"Start":"07:41.915 ","End":"07:44.570","Text":"That\u0027s less reduction in entropy than if many cages of"},{"Start":"07:44.570 ","End":"07:48.170","Text":"water molecules had to surround individual hydrophobic molecules."},{"Start":"07:48.170 ","End":"07:52.550","Text":"Although any single non-covalent bond is quite weak,"},{"Start":"07:52.550 ","End":"07:56.450","Text":"several such bonds between molecules or between the parts of 1 molecule,"},{"Start":"07:56.450 ","End":"08:01.555","Text":"can stabilize the 3-dimensional structure of proteins and nucleic acids,"},{"Start":"08:01.555 ","End":"08:04.550","Text":"and mediate specific binding interactions."},{"Start":"08:04.550 ","End":"08:10.160","Text":"Phospholipids, the main component of bio membranes, are amphipathic molecules."},{"Start":"08:10.160 ","End":"08:11.660","Text":"As you see here."},{"Start":"08:11.660 ","End":"08:18.800","Text":"They have a section that is hydrophilic and a section that is hydrophobic."},{"Start":"08:18.800 ","End":"08:24.000","Text":"A section that is polar and hydrophilic,"},{"Start":"08:24.160 ","End":"08:27.860","Text":"this is the head,"},{"Start":"08:27.860 ","End":"08:29.825","Text":"whereas you have the tail,"},{"Start":"08:29.825 ","End":"08:34.610","Text":"which is non-polar and hydrophobic,"},{"Start":"08:34.610 ","End":"08:37.430","Text":"meaning it wants to avoid water, repels it."},{"Start":"08:37.430 ","End":"08:40.955","Text":"These phospholipids that are amphipathic molecules,"},{"Start":"08:40.955 ","End":"08:42.845","Text":"which are the main components of bio membranes,"},{"Start":"08:42.845 ","End":"08:46.610","Text":"non-covalent bonds are responsible for organizing and stabilizing"},{"Start":"08:46.610 ","End":"08:53.135","Text":"phospholipids into 1 of 3 structures in aqueous solution."},{"Start":"08:53.135 ","End":"08:57.170","Text":"We have the single-layer lipid sphere,"},{"Start":"08:57.170 ","End":"09:01.700","Text":"we also call this the micelle or micelle."},{"Start":"09:01.700 ","End":"09:06.995","Text":"You then have the double-layer lipid bi-layer,"},{"Start":"09:06.995 ","End":"09:09.620","Text":"and this is a lipid bi-layer sphere,"},{"Start":"09:09.620 ","End":"09:18.140","Text":"which is made of the lipid bi-layer sheet that is in circular form."},{"Start":"09:18.140 ","End":"09:26.715","Text":"The basic structure of bio membranes consists of a phospholipid bi-layer, 1 layer,"},{"Start":"09:26.715 ","End":"09:30.890","Text":"2 layers, in which the long hydrocarbon"},{"Start":"09:30.890 ","End":"09:39.060","Text":"fatty acid side chains in each leaflet are oriented towards one another."},{"Start":"09:39.060 ","End":"09:41.420","Text":"If you see here, they\u0027re oriented."},{"Start":"09:41.420 ","End":"09:47.810","Text":"These tails, these fatty acyl side chains,"},{"Start":"09:47.810 ","End":"09:53.825","Text":"face each other, are oriented toward one another forming a hydrophobic core."},{"Start":"09:53.825 ","End":"09:57.470","Text":"This is the hydrophobic core which repels water."},{"Start":"09:57.470 ","End":"10:02.275","Text":"The polar head groups line both surfaces."},{"Start":"10:02.275 ","End":"10:06.660","Text":"They can interact and attract water."},{"Start":"10:06.660 ","End":"10:10.850","Text":"As an FYI, natural bio membranes also contain proteins, cholesterol,"},{"Start":"10:10.850 ","End":"10:15.200","Text":"and other components inserted into the phospholipid bi-layer."},{"Start":"10:15.200 ","End":"10:22.970","Text":"It is that within this array of multiple molecules that other things,"},{"Start":"10:22.970 ","End":"10:24.200","Text":"proteins or whatnot,"},{"Start":"10:24.200 ","End":"10:27.515","Text":"can embed and move along."},{"Start":"10:27.515 ","End":"10:33.105","Text":"With this, we completed the section of weak interaction\u0027s crucial role in life."},{"Start":"10:33.105 ","End":"10:36.020","Text":"You should be able to list the 4 types of non-covalent bonds,"},{"Start":"10:36.020 ","End":"10:38.630","Text":"describe the underlying force of these bonds,"},{"Start":"10:38.630 ","End":"10:41.059","Text":"and understand their significance to biology."},{"Start":"10:41.059 ","End":"10:46.300","Text":"Next, we can test our knowledge in the exercises in this section."}],"ID":28875},{"Watched":false,"Name":"Exercise 19","Duration":"3m 21s","ChapterTopicVideoID":27640,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.910","Text":"Hey there, welcome to exercise within the lesson"},{"Start":"00:02.910 ","End":"00:06.195","Text":"of Weak Interactions\u0027 Crucial Role in Life."},{"Start":"00:06.195 ","End":"00:10.620","Text":"Explain how though non-covalent bonds are weaker than covalent bonds,"},{"Start":"00:10.620 ","End":"00:15.510","Text":"these aren\u0027t easily disrupted between biomolecules and give an example."},{"Start":"00:15.510 ","End":"00:20.000","Text":"Well, these are all individually weaker than covalent bonds."},{"Start":"00:20.000 ","End":"00:24.530","Text":"The cumulative effect of any such interactions can be very significant."},{"Start":"00:24.530 ","End":"00:27.320","Text":"To dissociate 2 biomolecules non-covalently"},{"Start":"00:27.320 ","End":"00:30.613","Text":"associated through multiple weak interactions,"},{"Start":"00:30.613 ","End":"00:34.460","Text":"all these associations must be disrupted at the same time."},{"Start":"00:34.460 ","End":"00:38.660","Text":"All these interactions must be broken at the same time."},{"Start":"00:38.660 ","End":"00:43.271","Text":"Because these interactions are constantly fluctuating randomly,"},{"Start":"00:43.271 ","End":"00:45.980","Text":"such simultaneous disruptions are very unlikely."},{"Start":"00:45.980 ","End":"00:50.810","Text":"Therefore, 5 or 20 weak interactions bestow much greater molecular stability"},{"Start":"00:50.810 ","End":"00:56.320","Text":"than would be expected intuitively from a simple summation of small binding energies."},{"Start":"00:56.320 ","End":"01:00.910","Text":"Now, macromolecules such as proteins, DNA,"},{"Start":"01:00.910 ","End":"01:06.010","Text":"and RNA contain many sites of non-covalent bonding, hydrogen bonding,"},{"Start":"01:06.010 ","End":"01:10.150","Text":"ionic, hydrophobic, and/or Van der Waals interactions so that"},{"Start":"01:10.150 ","End":"01:15.714","Text":"the cumulative effect of the many small binding forces can be vast."},{"Start":"01:15.714 ","End":"01:17.635","Text":"We\u0027re asked to give an example."},{"Start":"01:17.635 ","End":"01:22.300","Text":"The non-covalent binding of an enzyme to its substrate may involve"},{"Start":"01:22.300 ","End":"01:27.880","Text":"several hydrogen bonds and 1 or more ionic interactions,"},{"Start":"01:27.880 ","End":"01:31.150","Text":"as well as hydrophobic and Van der Waals interactions."},{"Start":"01:31.150 ","End":"01:36.460","Text":"The energy released when an enzyme binds non-covalently,"},{"Start":"01:36.460 ","End":"01:43.130","Text":"so the energy released from this enzyme getting close and having a non-covalent bond."},{"Start":"01:43.130 ","End":"01:46.730","Text":"Here we see lines that represent hydrogen bonding,"},{"Start":"01:46.730 ","End":"01:49.940","Text":"ionic, and hydrophobic interactions."},{"Start":"01:49.940 ","End":"01:54.200","Text":"This energy released when it binds to"},{"Start":"01:54.200 ","End":"01:59.540","Text":"the substrate is the main source of the enzyme\u0027s catalytic power."},{"Start":"01:59.540 ","End":"02:04.880","Text":"The energy released when the enzyme binds non-covalently with"},{"Start":"02:04.880 ","End":"02:07.310","Text":"these different bonds to"},{"Start":"02:07.310 ","End":"02:11.280","Text":"its substrate is the main source of the enzyme\u0027s catalytic power,"},{"Start":"02:11.280 ","End":"02:14.135","Text":"so the ordered water interacting substrate and enzyme."},{"Start":"02:14.135 ","End":"02:20.555","Text":"Then it is moved aside so that the enzyme interacts non-covalently with the substrate"},{"Start":"02:20.555 ","End":"02:23.480","Text":"and now the water is displaced by"},{"Start":"02:23.480 ","End":"02:27.215","Text":"the enzyme substrate interaction and is more disordered."},{"Start":"02:27.215 ","End":"02:32.750","Text":"Therefore, we know that when order increases it means the energy is being released."},{"Start":"02:32.750 ","End":"02:37.160","Text":"This is the main source of the enzyme\u0027s catalytic power."},{"Start":"02:37.160 ","End":"02:40.670","Text":"Now, the binding of a hormone or a neurotransmitter to"},{"Start":"02:40.670 ","End":"02:45.820","Text":"its cellular receptor protein is the result of multiple weak interactions as well."},{"Start":"02:45.820 ","End":"02:50.000","Text":"Another example is the binding of an antigen to specific antibody."},{"Start":"02:50.000 ","End":"02:53.540","Text":"It depends on the cumulative effects of many weak interactions at"},{"Start":"02:53.540 ","End":"02:59.285","Text":"the different parts of the antibody binding to the antigen."},{"Start":"02:59.285 ","End":"03:01.730","Text":"A consequence of the large size of enzymes and"},{"Start":"03:01.730 ","End":"03:04.070","Text":"receptors relative to their substrates or ligands"},{"Start":"03:04.070 ","End":"03:10.415","Text":"is that their extensive surfaces provide many opportunities for weak interactions,"},{"Start":"03:10.415 ","End":"03:18.455","Text":"meaning there is the greater cumulative effect of this strength of the bonding."},{"Start":"03:18.455 ","End":"03:21.660","Text":"With that we completed this exercise."}],"ID":28876},{"Watched":false,"Name":"Exercise 20","Duration":"1m 36s","ChapterTopicVideoID":27641,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.270","Text":"We\u0027re back with another exercise in this section covering"},{"Start":"00:03.270 ","End":"00:09.255","Text":"Weak Interactions\u0027 Crucial Role in Life within the chapter of water and in a section,"},{"Start":"00:09.255 ","End":"00:11.775","Text":"topic of non-covalent bonds."},{"Start":"00:11.775 ","End":"00:13.485","Text":"Fill in the blanks."},{"Start":"00:13.485 ","End":"00:16.260","Text":"For macromolecules, the most,"},{"Start":"00:16.260 ","End":"00:18.495","Text":"blank, first blank,"},{"Start":"00:18.495 ","End":"00:21.650","Text":"thus native structure is that in which,"},{"Start":"00:21.650 ","End":"00:26.025","Text":"blank, second blank, interactions are maximized."},{"Start":"00:26.025 ","End":"00:29.010","Text":"We mentioned about macromolecules and here we\u0027re"},{"Start":"00:29.010 ","End":"00:31.815","Text":"talking about structure and the native structure,"},{"Start":"00:31.815 ","End":"00:37.230","Text":"meaning the one that forms naturally organically is that in which,"},{"Start":"00:37.230 ","End":"00:42.290","Text":"another blank, interactions are maximized."},{"Start":"00:42.290 ","End":"00:46.999","Text":"We talk about native being something that happens naturally,"},{"Start":"00:46.999 ","End":"00:50.915","Text":"so it needs to be stable."},{"Start":"00:50.915 ","End":"00:56.960","Text":"For macromolecules, the most stable thus native structure is that in which,"},{"Start":"00:56.960 ","End":"01:01.010","Text":"what interactions are maximized?"},{"Start":"01:01.010 ","End":"01:06.230","Text":"Macromolecules, the most stable, thus native structure is usually"},{"Start":"01:06.230 ","End":"01:12.055","Text":"that in which weak interactions are maximized."},{"Start":"01:12.055 ","End":"01:16.805","Text":"We will have several weak interactions and this will bring on"},{"Start":"01:16.805 ","End":"01:21.664","Text":"stability to remind you because even though these are weak interactions,"},{"Start":"01:21.664 ","End":"01:25.850","Text":"for the macromolecules association or structure to break,"},{"Start":"01:25.850 ","End":"01:28.850","Text":"you need all the weak interactions that are"},{"Start":"01:28.850 ","End":"01:33.275","Text":"present to break or dissociate at the same time."},{"Start":"01:33.275 ","End":"01:37.410","Text":"That is the end of this exercise."}],"ID":28877},{"Watched":false,"Name":"Exercise 21","Duration":"7m 14s","ChapterTopicVideoID":27642,"CourseChapterTopicPlaylistID":274666,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.460","Text":"Hi, we\u0027re still testing our knowledge within the chapter of water"},{"Start":"00:02.460 ","End":"00:05.250","Text":"on weak interactions crucial role in life."},{"Start":"00:05.250 ","End":"00:06.690","Text":"Which of the following statement is true?"},{"Start":"00:06.690 ","End":"00:09.840","Text":"A ionic bond is the strongest bond,"},{"Start":"00:09.840 ","End":"00:12.773","Text":"b hydrogen bonds are responsible for cohesive,"},{"Start":"00:12.773 ","End":"00:14.715","Text":"and adhesive properties of water."},{"Start":"00:14.715 ","End":"00:20.070","Text":"Hydrogen, water, van der Waals interactions are the strongest bond,"},{"Start":"00:20.070 ","End":"00:25.680","Text":"covalent bonds are the weakest bond. None of the above is true."},{"Start":"00:25.680 ","End":"00:31.930","Text":"We go back and say we talked about covalent bonds, and non-covalent bonds."},{"Start":"00:31.930 ","End":"00:39.590","Text":"We said that non-covalent bonds are generally weaker interactions than covalent bonds."},{"Start":"00:39.590 ","End":"00:49.220","Text":"Covalent bonds generally would be stronger than non-covalent bonds."},{"Start":"00:49.220 ","End":"00:52.910","Text":"Furthermore, we gave specific examples of non-covalent bonds,"},{"Start":"00:52.910 ","End":"00:56.645","Text":"and weak interactions in regard to water."},{"Start":"00:56.645 ","End":"01:00.995","Text":"Within this, we see some of them here."},{"Start":"01:00.995 ","End":"01:03.170","Text":"Ionic bonds, hydrogen bonds,"},{"Start":"01:03.170 ","End":"01:05.135","Text":"van der Waals interactions."},{"Start":"01:05.135 ","End":"01:09.635","Text":"All these fall within the non-covalent bonds,"},{"Start":"01:09.635 ","End":"01:12.275","Text":"which in essence it would mean,"},{"Start":"01:12.275 ","End":"01:15.335","Text":"okay, they\u0027re probably weaker than covalent bonds."},{"Start":"01:15.335 ","End":"01:18.440","Text":"Covalent bonds, therefore, are not the weakest bond."},{"Start":"01:18.440 ","End":"01:20.870","Text":"Let\u0027s go now, one at a time."},{"Start":"01:20.870 ","End":"01:24.590","Text":"Ionic bonds. The ionic bond is the strongest bond."},{"Start":"01:24.590 ","End":"01:28.655","Text":"Well, a bond between ions is a strong bond."},{"Start":"01:28.655 ","End":"01:30.995","Text":"There\u0027s an attraction between"},{"Start":"01:30.995 ","End":"01:35.465","Text":"opposite charges of each one of the ion, the positive and the negative."},{"Start":"01:35.465 ","End":"01:37.970","Text":"Yet it is still a non-covalent bond,"},{"Start":"01:37.970 ","End":"01:44.300","Text":"and therefore can\u0027t be the strongest bond because there\u0027s a covalent bond that stronger."},{"Start":"01:44.300 ","End":"01:46.789","Text":"Now, just looking over,"},{"Start":"01:46.789 ","End":"01:48.860","Text":"we also have, I mentioned here,"},{"Start":"01:48.860 ","End":"01:50.840","Text":"a Van der Waals interactions as being the strongest."},{"Start":"01:50.840 ","End":"01:53.780","Text":"For sure, if one of them is true,"},{"Start":"01:53.780 ","End":"01:55.370","Text":"the other one can\u0027t be true."},{"Start":"01:55.370 ","End":"02:00.965","Text":"We know that it can\u0027t be both a and c. One of them for sure is incorrect."},{"Start":"02:00.965 ","End":"02:03.635","Text":"We know that at least from a through e,"},{"Start":"02:03.635 ","End":"02:05.330","Text":"either a or c are incorrect,"},{"Start":"02:05.330 ","End":"02:09.450","Text":"and we just said ionic bonds are non-covalent therefore,"},{"Start":"02:09.450 ","End":"02:12.485","Text":"even though they\u0027re stronger bonds than others,"},{"Start":"02:12.485 ","End":"02:13.730","Text":"they\u0027re not the strongest."},{"Start":"02:13.730 ","End":"02:15.185","Text":"Let\u0027s move to hydrogen bonds."},{"Start":"02:15.185 ","End":"02:17.180","Text":"These bonds are responsible for cohesive,"},{"Start":"02:17.180 ","End":"02:18.710","Text":"and adhesive properties of the water."},{"Start":"02:18.710 ","End":"02:20.615","Text":"Remember we talked about molecules."},{"Start":"02:20.615 ","End":"02:25.550","Text":"We have the oxygen molecule that has a partial negative charge,"},{"Start":"02:25.550 ","End":"02:31.885","Text":"and we have the hydrogen molecules that have a partial positive charge."},{"Start":"02:31.885 ","End":"02:36.355","Text":"This is our water molecule, so oxygen, hydrogen."},{"Start":"02:36.355 ","End":"02:39.730","Text":"Once you get another water molecule,"},{"Start":"02:39.730 ","End":"02:42.910","Text":"another H2O, these opposite partial charges,"},{"Start":"02:42.910 ","End":"02:45.250","Text":"the dipole that\u0027s created in the water molecule,"},{"Start":"02:45.250 ","End":"02:47.260","Text":"negative pull positive,"},{"Start":"02:47.260 ","End":"02:55.780","Text":"allows for this hydrogen bond between hydrogen molecules, water molecules."},{"Start":"02:55.780 ","End":"03:00.370","Text":"This can keep on going in a chain where you have"},{"Start":"03:00.370 ","End":"03:06.660","Text":"these hydrogen bonds with another molecule and another molecule."},{"Start":"03:06.660 ","End":"03:08.883","Text":"Imagine this is a person,"},{"Start":"03:08.883 ","End":"03:10.570","Text":"and these are his 2 hands,"},{"Start":"03:10.570 ","End":"03:15.440","Text":"and imagine a party and a conga line or a massage chain or whatever."},{"Start":"03:15.440 ","End":"03:21.450","Text":"This person can put his hand on one person."},{"Start":"03:21.450 ","End":"03:25.700","Text":"His left hand is on one person and his right hand is on another person."},{"Start":"03:25.700 ","End":"03:27.590","Text":"Now they\u0027re not glued together."},{"Start":"03:27.590 ","End":"03:31.490","Text":"They just placed it on their shoulder or on their back."},{"Start":"03:31.490 ","End":"03:33.980","Text":"It can easily be disconnected."},{"Start":"03:33.980 ","End":"03:36.995","Text":"But, still if you had these 2 hands on 2 people\u0027s shoulders,"},{"Start":"03:36.995 ","End":"03:40.745","Text":"and the person in front on the left also has his hand on another person,"},{"Start":"03:40.745 ","End":"03:43.115","Text":"and then his right hand on another person,"},{"Start":"03:43.115 ","End":"03:51.326","Text":"basically what you end"},{"Start":"03:51.326 ","End":"03:54.380","Text":"up having is a cluster of people that are interlinked with"},{"Start":"03:54.380 ","End":"03:59.540","Text":"this transient link of hands being on someone\u0027s shoulder or back or neck."},{"Start":"03:59.540 ","End":"04:04.970","Text":"If someone wants to cross through this cluster of people that is not connected to them,"},{"Start":"04:04.970 ","End":"04:10.700","Text":"it will be really hard because this cluster creates somewhat of a barrier."},{"Start":"04:10.700 ","End":"04:16.625","Text":"This cluster of hydrogen bonds create a barrier on which"},{"Start":"04:16.625 ","End":"04:20.150","Text":"light quick organisms can run across the surface of water"},{"Start":"04:20.150 ","End":"04:24.485","Text":"because the water molecules are bonded together in these hydrogens sticky bonds."},{"Start":"04:24.485 ","End":"04:28.340","Text":"This is why also when you put a floaty on top of water,"},{"Start":"04:28.340 ","End":"04:30.830","Text":"it floats on top of the water because it\u0027s"},{"Start":"04:30.830 ","End":"04:34.580","Text":"light enough that it doesn\u0027t break this cluster,"},{"Start":"04:34.580 ","End":"04:39.315","Text":"these hydrogen bonds, these non-covalent bonds."},{"Start":"04:39.315 ","End":"04:42.255","Text":"This seems like it could be true."},{"Start":"04:42.255 ","End":"04:44.920","Text":"We know a is not true,"},{"Start":"04:44.920 ","End":"04:46.625","Text":"b may be true."},{"Start":"04:46.625 ","End":"04:51.390","Text":"Let\u0027s talk about c. Van der Waals interactions are the strongest bond."},{"Start":"04:51.390 ","End":"04:57.550","Text":"Well, Van der Waals is something we learned, and non-covalent bonds."},{"Start":"04:57.550 ","End":"05:02.155","Text":"Furthermore, you have a hint because it says interactions as being the strongest bond."},{"Start":"05:02.155 ","End":"05:04.960","Text":"An interaction versus a bond,"},{"Start":"05:04.960 ","End":"05:08.215","Text":"just by definition, seems a little weaker."},{"Start":"05:08.215 ","End":"05:11.979","Text":"Van der Waals interactions occur when 2 molecules, it\u0027s like transient."},{"Start":"05:11.979 ","End":"05:16.195","Text":"When 2 molecules are close enough to each other that they can interact,"},{"Start":"05:16.195 ","End":"05:21.545","Text":"that they can have this semi-transient bond between them."},{"Start":"05:21.545 ","End":"05:24.515","Text":"But the minute the molecules are too far apart,"},{"Start":"05:24.515 ","End":"05:28.535","Text":"this can\u0027t occur and/or the interaction will break."},{"Start":"05:28.535 ","End":"05:31.100","Text":"If we think there\u0027s a strong bond,"},{"Start":"05:31.100 ","End":"05:32.630","Text":"let\u0027s say between 2 magnets,"},{"Start":"05:32.630 ","End":"05:35.210","Text":"if it\u0027s a strong bond between these 2 magnets,"},{"Start":"05:35.210 ","End":"05:36.440","Text":"even if you hold them far apart,"},{"Start":"05:36.440 ","End":"05:40.690","Text":"you\u0027ll have to engage force to keep them apart from each other."},{"Start":"05:40.690 ","End":"05:41.960","Text":"If you let go of one,"},{"Start":"05:41.960 ","End":"05:43.835","Text":"it will just go and stick to the other one."},{"Start":"05:43.835 ","End":"05:46.790","Text":"But if it\u0027s a weak magnet and you hold them at"},{"Start":"05:46.790 ","End":"05:51.795","Text":"the same distance from each other as the previous strong interaction magnetic bond,"},{"Start":"05:51.795 ","End":"05:53.180","Text":"and you release one of them,"},{"Start":"05:53.180 ","End":"05:56.195","Text":"it will fall to the ground because the force between them"},{"Start":"05:56.195 ","End":"05:59.805","Text":"is not strong enough to overcome the force of gravity, for example."},{"Start":"05:59.805 ","End":"06:02.270","Text":"If this example helped illustrate the idea, great."},{"Start":"06:02.270 ","End":"06:05.450","Text":"If it confused, you don\u0027t worry about it or listen to it again."},{"Start":"06:05.450 ","End":"06:08.225","Text":"But the idea is that a van der Waals interaction,"},{"Start":"06:08.225 ","End":"06:12.050","Text":"not very strong, needs proximity for it to occur."},{"Start":"06:12.050 ","End":"06:15.160","Text":"We can say that c is incorrect as well."},{"Start":"06:15.160 ","End":"06:17.990","Text":"Next, covalent bonds are the weakest bond."},{"Start":"06:17.990 ","End":"06:21.620","Text":"Well, we mentioned covalent bonds as being stronger than non-covalent bonds,"},{"Start":"06:21.620 ","End":"06:23.540","Text":"therefore, it cannot be the weakest bond."},{"Start":"06:23.540 ","End":"06:26.450","Text":"Actually covalent bonds are strong bonds between"},{"Start":"06:26.450 ","End":"06:31.245","Text":"molecules within organisms, or materials."},{"Start":"06:31.245 ","End":"06:36.725","Text":"This also could be deemed incorrect and that leaves us with e or b. E,"},{"Start":"06:36.725 ","End":"06:38.060","Text":"none of the above is true."},{"Start":"06:38.060 ","End":"06:40.850","Text":"This can be true if b is untrue,"},{"Start":"06:40.850 ","End":"06:44.740","Text":"and b can be true if e is untrue."},{"Start":"06:44.740 ","End":"06:48.920","Text":"B, hydrogen bonds are responsible for cohesive and adhesive properties of the water."},{"Start":"06:48.920 ","End":"06:53.600","Text":"We go back to the explanation of hydrogen bonding and yes, this makes sense."},{"Start":"06:53.600 ","End":"06:55.205","Text":"We actually covered this."},{"Start":"06:55.205 ","End":"06:59.030","Text":"This contributes to waters melting point,"},{"Start":"06:59.030 ","End":"07:01.465","Text":"vapor point, boiling point,"},{"Start":"07:01.465 ","End":"07:04.625","Text":"so we can say this sounds true."},{"Start":"07:04.625 ","End":"07:06.380","Text":"This therefore is not true."},{"Start":"07:06.380 ","End":"07:08.735","Text":"Mark this off and we are left with b."},{"Start":"07:08.735 ","End":"07:11.390","Text":"The true statement is that hydrogen bonds are responsible"},{"Start":"07:11.390 ","End":"07:15.150","Text":"for cohesive and adhesive properties of water."}],"ID":28878}],"Thumbnail":null,"ID":274666},{"Name":"Colligative Properties","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Introduction To Colligative Properties Part 1","Duration":"9m 56s","ChapterTopicVideoID":27414,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.305","Text":"Hi there, welcome to colligative properties within the chapter on water."},{"Start":"00:04.305 ","End":"00:08.280","Text":"Here we\u0027ll deal with the introduction to colligative properties."},{"Start":"00:08.280 ","End":"00:11.460","Text":"By the end of this section, you\u0027ll be able to define colligative properties,"},{"Start":"00:11.460 ","End":"00:14.160","Text":"understand osmosis and its function in solutions,"},{"Start":"00:14.160 ","End":"00:17.830","Text":"and establish the significance of these properties in organisms."},{"Start":"00:17.830 ","End":"00:20.285","Text":"Now, we\u0027re going to split this into 2 parts."},{"Start":"00:20.285 ","End":"00:24.180","Text":"In Part 1, we will focus on defining colligative properties,"},{"Start":"00:24.180 ","End":"00:28.305","Text":"understanding osmosis and its function in solutions, and define diffusion."},{"Start":"00:28.305 ","End":"00:33.180","Text":"Solutes of all kinds alter certain physical properties of the solvent, water."},{"Start":"00:33.180 ","End":"00:36.135","Text":"These are, its vapor pressure,"},{"Start":"00:36.135 ","End":"00:43.255","Text":"boiling point, melting point or freezing point, and osmotic pressure."},{"Start":"00:43.255 ","End":"00:46.280","Text":"These are called colligative properties."},{"Start":"00:46.280 ","End":"00:49.910","Text":"Colligative itself means tied together."},{"Start":"00:49.910 ","End":"00:53.855","Text":"Now the effects of solutes on all 4 properties has the same basis."},{"Start":"00:53.855 ","End":"00:58.505","Text":"The concentration of water is lower in solutions than in pure water."},{"Start":"00:58.505 ","End":"01:04.280","Text":"Concentration of water is lower when it\u0027s in a solution than in pure water."},{"Start":"01:04.280 ","End":"01:13.670","Text":"Pure water, higher concentration than water in solution, aqueous."},{"Start":"01:13.670 ","End":"01:15.515","Text":"Remember solution?"},{"Start":"01:15.515 ","End":"01:20.620","Text":"This is concentration."},{"Start":"01:20.620 ","End":"01:23.160","Text":"Now, just to remind you also,"},{"Start":"01:23.160 ","End":"01:28.030","Text":"these brackets also define that we\u0027re looking in a concentration."},{"Start":"01:28.030 ","End":"01:32.260","Text":"Next, the effect of solute concentration on the colligative properties"},{"Start":"01:32.260 ","End":"01:36.310","Text":"of water is independent of the chemical properties of the solute."},{"Start":"01:36.310 ","End":"01:41.365","Text":"Rather, it depends solely on the number of solute particles,"},{"Start":"01:41.365 ","End":"01:44.380","Text":"molecules, or ions in a given amount of water."},{"Start":"01:44.380 ","End":"01:48.520","Text":"A compound such as NaCl, sodium chloride,"},{"Start":"01:48.520 ","End":"01:50.605","Text":"salt, which we mentioned previously,"},{"Start":"01:50.605 ","End":"01:52.900","Text":"which dissociates in solution,"},{"Start":"01:52.900 ","End":"01:55.810","Text":"has an effect on osmotic pressure that is twice that of"},{"Start":"01:55.810 ","End":"01:58.900","Text":"an equal number of moles of a non-dissociating solute,"},{"Start":"01:58.900 ","End":"02:02.020","Text":"meaning a solute that does not break apart in water."},{"Start":"02:02.020 ","End":"02:05.725","Text":"Glucose can be an example of this."},{"Start":"02:05.725 ","End":"02:08.675","Text":"Looking at NaCl, sodium chloride,"},{"Start":"02:08.675 ","End":"02:11.420","Text":"when you put it in solution in water,"},{"Start":"02:11.420 ","End":"02:14.450","Text":"it becomes Na plus and Cl minus."},{"Start":"02:14.450 ","End":"02:17.595","Text":"It breaks apart into the 2 ions, into 2."},{"Start":"02:17.595 ","End":"02:22.710","Text":"It\u0027s 2 ions, which means from 1 molecule of NaCl now has 2 molecules."},{"Start":"02:22.710 ","End":"02:30.185","Text":"If you put this in a solution of water and it breaks up into this,"},{"Start":"02:30.185 ","End":"02:35.210","Text":"you now have instead of 1 molecule, 2 molecules."},{"Start":"02:35.210 ","End":"02:39.770","Text":"Now, if you put glucose in water and it doesn\u0027t dissociate,"},{"Start":"02:39.770 ","End":"02:42.395","Text":"it stays glucose,"},{"Start":"02:42.395 ","End":"02:45.775","Text":"then you have 1 molecule,"},{"Start":"02:45.775 ","End":"02:49.020","Text":"but here it remains 1."},{"Start":"02:49.020 ","End":"02:50.930","Text":"In the same,"},{"Start":"02:50.930 ","End":"02:52.475","Text":"if you have containers,"},{"Start":"02:52.475 ","End":"02:56.350","Text":"even though, let\u0027s say you put in the container,"},{"Start":"02:56.350 ","End":"03:02.525","Text":"8 molecules of each glucose and 8 molecules of sodium chloride, of salt,"},{"Start":"03:02.525 ","End":"03:06.890","Text":"you are left with 8 molecules in the solution,"},{"Start":"03:06.890 ","End":"03:10.070","Text":"whereas sodium chloride dissociates into the 2 ions,"},{"Start":"03:10.070 ","End":"03:13.705","Text":"so now these 8 molecules of sodium chloride become"},{"Start":"03:13.705 ","End":"03:18.855","Text":"8 molecules of sodium ion and 8 molecules of chloride ion,"},{"Start":"03:18.855 ","End":"03:24.870","Text":"and that makes it 16 molecules versus 8."},{"Start":"03:24.870 ","End":"03:30.925","Text":"Basically, it means that the effect on osmotic pressure is twice that of"},{"Start":"03:30.925 ","End":"03:32.780","Text":"an equal amount of moles of"},{"Start":"03:32.780 ","End":"03:37.625","Text":"a non-dissociating solute in comparison to a solute that dissociates."},{"Start":"03:37.625 ","End":"03:40.700","Text":"Water molecules tend to move from a region of"},{"Start":"03:40.700 ","End":"03:44.795","Text":"higher water concentration to a region of lower concentration."},{"Start":"03:44.795 ","End":"03:50.855","Text":"We just mentioned that water is lower in concentration solutions."},{"Start":"03:50.855 ","End":"03:54.470","Text":"It means it\u0027s moving from higher water concentration to low concentration,"},{"Start":"03:54.470 ","End":"03:59.710","Text":"we mentioned pure water and solution."},{"Start":"03:59.710 ","End":"04:02.675","Text":"It makes sense that they will move"},{"Start":"04:02.675 ","End":"04:06.500","Text":"from the pure water to the solution where it\u0027s lower concentration."},{"Start":"04:06.500 ","End":"04:12.665","Text":"This is in accordance with nature\u0027s tendency and preference to become disordered."},{"Start":"04:12.665 ","End":"04:16.110","Text":"When 2 different aqueous solutions are separated by a semipermeable membrane,"},{"Start":"04:16.110 ","End":"04:18.950","Text":"this is a membrane that allows the passage of water but not of"},{"Start":"04:18.950 ","End":"04:22.220","Text":"solute molecules, semipermeable,"},{"Start":"04:22.220 ","End":"04:27.970","Text":"then water molecules diffusing, transferring,"},{"Start":"04:27.970 ","End":"04:35.060","Text":"moving from the region with a higher concentration of water to"},{"Start":"04:35.060 ","End":"04:42.785","Text":"one with lower concentration of water produces osmotic pressure."},{"Start":"04:42.785 ","End":"04:46.700","Text":"These differences in concentration that result in the movement of"},{"Start":"04:46.700 ","End":"04:51.035","Text":"water molecules is osmotic pressure."},{"Start":"04:51.035 ","End":"04:53.015","Text":"If you look at this example,"},{"Start":"04:53.015 ","End":"04:57.740","Text":"it should have start with this cup having the same amount,"},{"Start":"04:57.740 ","End":"05:00.461","Text":"the same level of freshwater and salt water."},{"Start":"05:00.461 ","End":"05:03.200","Text":"But because you have a higher concentration of water"},{"Start":"05:03.200 ","End":"05:06.125","Text":"here and a lower concentration of water here,"},{"Start":"05:06.125 ","End":"05:09.755","Text":"the water molecules will move in the direction of the lower concentration,"},{"Start":"05:09.755 ","End":"05:15.090","Text":"and therefore the water level change from the original water level and went down in"},{"Start":"05:15.090 ","End":"05:20.560","Text":"the bottle of almost salt water because some had diffused the results in the movement."},{"Start":"05:20.560 ","End":"05:25.760","Text":"This movement across the semipermeable membrane is osmotic pressure."},{"Start":"05:25.760 ","End":"05:28.355","Text":"Now, just to show osmotic pressure,"},{"Start":"05:28.355 ","End":"05:30.409","Text":"there is also reverse osmosis."},{"Start":"05:30.409 ","End":"05:33.185","Text":"By intuition you\u0027d say, \"Then it\u0027s the reverse of it.\""},{"Start":"05:33.185 ","End":"05:35.894","Text":"Instead of water moving as it naturally should,"},{"Start":"05:35.894 ","End":"05:37.790","Text":"from a high concentration to a low concentration,"},{"Start":"05:37.790 ","End":"05:40.265","Text":"reverse osmosis is that water molecules moves"},{"Start":"05:40.265 ","End":"05:43.385","Text":"from a low concentration of water molecules to a higher concentration,"},{"Start":"05:43.385 ","End":"05:47.205","Text":"and this will happen because there is pressure that\u0027s asserted"},{"Start":"05:47.205 ","End":"05:51.630","Text":"on the system leading to reverse osmosis."},{"Start":"05:51.630 ","End":"05:54.500","Text":"Physical pressure on the salt water,"},{"Start":"05:54.500 ","End":"05:56.780","Text":"like having a piston,"},{"Start":"05:56.780 ","End":"06:00.025","Text":"a plunger, air, vapor,"},{"Start":"06:00.025 ","End":"06:03.160","Text":"will push down physically on the salt water,"},{"Start":"06:03.160 ","End":"06:09.910","Text":"where it causes force of the water molecules to move against the natural reverse osmosis."},{"Start":"06:09.910 ","End":"06:13.180","Text":"Let\u0027s define diffusion. Diffusion is the net movement of"},{"Start":"06:13.180 ","End":"06:16.990","Text":"substance from a region of higher concentration to a region of lower concentration."},{"Start":"06:16.990 ","End":"06:22.345","Text":"If you\u0027re looking here, now we have expanded from osmosis as we talked about with water."},{"Start":"06:22.345 ","End":"06:24.505","Text":"Rather, here it\u0027s net movement of"},{"Start":"06:24.505 ","End":"06:28.840","Text":"any substance from higher concentration to lower concentration."},{"Start":"06:28.840 ","End":"06:31.750","Text":"Here you see there\u0027s a lot of these red polka dots."},{"Start":"06:31.750 ","End":"06:34.585","Text":"You can consider the polka dots anything you want,"},{"Start":"06:34.585 ","End":"06:36.230","Text":"any molecule you want."},{"Start":"06:36.230 ","End":"06:42.625","Text":"Maybe it\u0027s people in an elevator that\u0027s super crowded and after the whole COVID thing,"},{"Start":"06:42.625 ","End":"06:44.969","Text":"you don\u0027t want to be in a crowded elevator in general."},{"Start":"06:44.969 ","End":"06:46.900","Text":"Who wants to be in a crowded elevator?"},{"Start":"06:46.900 ","End":"06:48.685","Text":"You go to the other elevator that has"},{"Start":"06:48.685 ","End":"06:51.865","Text":"less people because the doors open between the elevators."},{"Start":"06:51.865 ","End":"06:54.535","Text":"You have a lot of dots here, less dots here."},{"Start":"06:54.535 ","End":"06:57.640","Text":"The chemical driving force of the diffusion."},{"Start":"06:57.640 ","End":"07:02.445","Text":"These molecules will diffuse to the lower concentration,"},{"Start":"07:02.445 ","End":"07:04.605","Text":"so you\u0027ll see movement out."},{"Start":"07:04.605 ","End":"07:06.220","Text":"Here you see the opposite."},{"Start":"07:06.220 ","End":"07:10.660","Text":"There\u0027s only few dots in here versus many dots out there,"},{"Start":"07:10.660 ","End":"07:12.580","Text":"and it\u0027s crowded out here."},{"Start":"07:12.580 ","End":"07:14.170","Text":"We all want to go in."},{"Start":"07:14.170 ","End":"07:17.755","Text":"The chemical driving force is to go in to the lower concentration."},{"Start":"07:17.755 ","End":"07:20.080","Text":"That is diffusion."},{"Start":"07:20.080 ","End":"07:22.705","Text":"Now, although each molecule moves randomly,"},{"Start":"07:22.705 ","End":"07:27.740","Text":"it\u0027s not like there\u0027s a path that this molecule has to move on."},{"Start":"07:27.740 ","End":"07:33.440","Text":"Diffusion of molecules as a whole maybe and generally is directional by"},{"Start":"07:33.440 ","End":"07:36.125","Text":"actually definition because there\u0027s a net movement of"},{"Start":"07:36.125 ","End":"07:39.905","Text":"a substance from a region of higher concentration to lower concentration."},{"Start":"07:39.905 ","End":"07:43.070","Text":"As you see, the general movement,"},{"Start":"07:43.070 ","End":"07:48.320","Text":"the general direction of the diffusion will be from up here to down here, will be down."},{"Start":"07:48.320 ","End":"07:50.285","Text":"If you look in here,"},{"Start":"07:50.285 ","End":"07:55.415","Text":"you will see downward movement of pure water versus water in solution,"},{"Start":"07:55.415 ","End":"07:56.660","Text":"which is lower concentration."},{"Start":"07:56.660 ","End":"07:58.190","Text":"You\u0027ll see diffusion going from"},{"Start":"07:58.190 ","End":"08:01.010","Text":"a higher concentration of water to lower concentration of water."},{"Start":"08:01.010 ","End":"08:02.675","Text":"We mentioned reverse osmosis."},{"Start":"08:02.675 ","End":"08:05.440","Text":"You have pressure that\u0027s pressing down on this,"},{"Start":"08:05.440 ","End":"08:07.970","Text":"so it\u0027s causing a higher pressure"},{"Start":"08:07.970 ","End":"08:11.510","Text":"here that in essence can be the equivalent of concentration."},{"Start":"08:11.510 ","End":"08:15.845","Text":"Higher here, push through and it goes to this side."},{"Start":"08:15.845 ","End":"08:22.654","Text":"Now, dynamic equilibrium, 2 terms we\u0027ve mentioned in previous lessons."},{"Start":"08:22.654 ","End":"08:26.300","Text":"Dynamic, that is constantly moving, it\u0027s not static."},{"Start":"08:26.300 ","End":"08:30.775","Text":"Equilibrium, equal, so dynamic equilibrium."},{"Start":"08:30.775 ","End":"08:35.300","Text":"This term refers to when molecules cross the membrane equally in both directions."},{"Start":"08:35.300 ","End":"08:37.100","Text":"Basically, there is an equilibrium,"},{"Start":"08:37.100 ","End":"08:40.925","Text":"there\u0027s an equal concentration in the 2 different regions."},{"Start":"08:40.925 ","End":"08:44.690","Text":"The region inside here and the region outside, it\u0027s equal concentrations."},{"Start":"08:44.690 ","End":"08:48.210","Text":"Here you see also many molecules outside,"},{"Start":"08:48.210 ","End":"08:49.560","Text":"many inside."},{"Start":"08:49.560 ","End":"08:50.820","Text":"It\u0027s equal concentrations."},{"Start":"08:50.820 ","End":"08:54.950","Text":"What happens, you have the molecules crossing the membrane equally in both directions,"},{"Start":"08:54.950 ","End":"08:59.240","Text":"constantly going in and out because there\u0027s equilibrium and it\u0027s dynamic because"},{"Start":"08:59.240 ","End":"09:03.845","Text":"there is this constant movement in both directions."},{"Start":"09:03.845 ","End":"09:07.145","Text":"If you look here, and we basically apply this to"},{"Start":"09:07.145 ","End":"09:10.550","Text":"what we\u0027ve talked about in biology of organisms,"},{"Start":"09:10.550 ","End":"09:13.564","Text":"life of organisms, we talk about the lipid bilayer."},{"Start":"09:13.564 ","End":"09:15.973","Text":"We define membranes of organelles and things,"},{"Start":"09:15.973 ","End":"09:22.655","Text":"and the cell itself as being made up of these many phospholipid heads."},{"Start":"09:22.655 ","End":"09:25.595","Text":"These associate with each other,"},{"Start":"09:25.595 ","End":"09:29.180","Text":"yet not actually covalently bound to each"},{"Start":"09:29.180 ","End":"09:33.620","Text":"other in a way that does allow diffusion through the lipid bilayer."},{"Start":"09:33.620 ","End":"09:36.455","Text":"You\u0027ll see high concentration here, low concentration here."},{"Start":"09:36.455 ","End":"09:39.920","Text":"It allows the simple diffusion through the lipid bilayer."},{"Start":"09:39.920 ","End":"09:43.970","Text":"With that, we completed Part 1 of the introduction to colligative properties."},{"Start":"09:43.970 ","End":"09:46.730","Text":"You should be able to define colligative properties,"},{"Start":"09:46.730 ","End":"09:50.720","Text":"understand osmosis and its function in solutions, and define diffusion."},{"Start":"09:50.720 ","End":"09:56.490","Text":"We will further go into this topic and expand on our knowledge in Part 2."}],"ID":28498},{"Watched":false,"Name":"Introduction To Colligative Properties Part 2","Duration":"7m 24s","ChapterTopicVideoID":27415,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.710 ","End":"00:06.524","Text":"Welcome to Part 2 of Introduction to Colligative Properties within the chapter of Water."},{"Start":"00:06.524 ","End":"00:08.729","Text":"By the end of this section,"},{"Start":"00:08.729 ","End":"00:12.990","Text":"you will be able to further define colligative properties,"},{"Start":"00:12.990 ","End":"00:16.155","Text":"describe tonicity, and explain osmotic pressure."},{"Start":"00:16.155 ","End":"00:19.005","Text":"Let\u0027s define another term, tonicity."},{"Start":"00:19.005 ","End":"00:20.370","Text":"Think of tonic water."},{"Start":"00:20.370 ","End":"00:23.520","Text":"Tonicity, the relative concentration of solutes"},{"Start":"00:23.520 ","End":"00:27.180","Text":"dissolved in a solution which determines the direction and extent of osmosis."},{"Start":"00:27.180 ","End":"00:29.130","Text":"So tonic water isn\u0027t just water."},{"Start":"00:29.130 ","End":"00:30.420","Text":"There\u0027s something else in it,"},{"Start":"00:30.420 ","End":"00:32.495","Text":"some molecules that make it flavorful."},{"Start":"00:32.495 ","End":"00:36.060","Text":"So tonicity, it has to do with solutions."},{"Start":"00:36.060 ","End":"00:39.395","Text":"Next we are going back to the term osmolarity."},{"Start":"00:39.395 ","End":"00:43.136","Text":"This is far as a solution\u0027s total solute concentration,"},{"Start":"00:43.136 ","End":"00:47.959","Text":"so the concentration of the things that are dissolved in the solvent."},{"Start":"00:47.959 ","End":"00:53.270","Text":"This concentration and osmolarity that is affected by the tonicity,"},{"Start":"00:53.270 ","End":"00:54.875","Text":"the concentration of the solutes,"},{"Start":"00:54.875 ","End":"00:58.715","Text":"can actually have different definitions,"},{"Start":"00:58.715 ","End":"01:01.355","Text":"and we are going to go over these right now."},{"Start":"01:01.355 ","End":"01:03.695","Text":"We\u0027re going to start with isotonic solutions."},{"Start":"01:03.695 ","End":"01:06.230","Text":"\"Iso\", isotonic means that"},{"Start":"01:06.230 ","End":"01:10.980","Text":"the extracellular fluid has the same osmolarity as the cell\u0027s cytoplasm."},{"Start":"01:10.980 ","End":"01:15.485","Text":"So if we\u0027re comparing a cell inside and outside,"},{"Start":"01:15.485 ","End":"01:20.660","Text":"it means that it\u0027s the same osmolarity, the same concentrations."},{"Start":"01:20.660 ","End":"01:24.950","Text":"So this would be like looking at these: the inside of the cell,"},{"Start":"01:24.950 ","End":"01:26.375","Text":"and the extracellular material,"},{"Start":"01:26.375 ","End":"01:30.050","Text":"the cytoplasm, cytoplasm, extracellular material."},{"Start":"01:30.050 ","End":"01:36.815","Text":"They are equal between the cell cytoplasm and the extracellular fluid."},{"Start":"01:36.815 ","End":"01:38.420","Text":"If you look here, isotonic,"},{"Start":"01:38.420 ","End":"01:40.535","Text":"that means that movement in and out,"},{"Start":"01:40.535 ","End":"01:43.790","Text":"this dynamic equilibrium, is equal."},{"Start":"01:43.790 ","End":"01:47.255","Text":"This is our equal case of concentration."},{"Start":"01:47.255 ","End":"01:50.420","Text":"Next we have hypotonic solutions."},{"Start":"01:50.420 ","End":"01:57.038","Text":"\"Hypo\", the extracellular fluid has lower osmolarity than the fluid inside the cell,"},{"Start":"01:57.038 ","End":"02:01.145","Text":"meaning, there\u0027s a lower concentration of water inside the cell,"},{"Start":"02:01.145 ","End":"02:05.180","Text":"resulting in water moving into the cell."},{"Start":"02:05.180 ","End":"02:06.830","Text":"If there is no control of this,"},{"Start":"02:06.830 ","End":"02:08.900","Text":"the cell can end up lysing, breaking,"},{"Start":"02:08.900 ","End":"02:14.408","Text":"bursting because so much water is going to move in to try to reach equal concentrations,"},{"Start":"02:14.408 ","End":"02:17.501","Text":"yet the membrane can\u0027t be expanded anymore,"},{"Start":"02:17.501 ","End":"02:19.400","Text":"and it bursts like a balloon."},{"Start":"02:19.400 ","End":"02:21.340","Text":"You put too much air in a balloon, it will burst."},{"Start":"02:21.340 ","End":"02:23.390","Text":"Water, put too much water in a balloon,"},{"Start":"02:23.390 ","End":"02:26.134","Text":"the osmotic pressure against"},{"Start":"02:26.134 ","End":"02:30.440","Text":"the actual rubber of the balloon is so high that the balloon bursts."},{"Start":"02:30.440 ","End":"02:34.010","Text":"Next we have, last but not least, hypertonic solutions."},{"Start":"02:34.010 ","End":"02:37.460","Text":"\"Hyper\", hyperactive, it means excess,"},{"Start":"02:37.460 ","End":"02:39.350","Text":"so it means the extracellular fluid has"},{"Start":"02:39.350 ","End":"02:43.520","Text":"a higher osmolarity than the cell cytoplasm, meaning,"},{"Start":"02:43.520 ","End":"02:45.259","Text":"it has a higher concentration,"},{"Start":"02:45.259 ","End":"02:48.890","Text":"which means that higher osmolarity,"},{"Start":"02:48.890 ","End":"02:50.090","Text":"higher concentration of solids,"},{"Start":"02:50.090 ","End":"02:53.300","Text":"meaning lower concentration of water."},{"Start":"02:53.300 ","End":"02:57.665","Text":"So water is going to move from the cell out to the extracellular fluid,"},{"Start":"02:57.665 ","End":"03:01.040","Text":"and the cell will then shrivel up."},{"Start":"03:01.040 ","End":"03:03.230","Text":"You may think that these looked like blood cells."},{"Start":"03:03.230 ","End":"03:05.525","Text":"They are, but this is not about blood cell."},{"Start":"03:05.525 ","End":"03:07.895","Text":"This is just to depict the idea."},{"Start":"03:07.895 ","End":"03:10.715","Text":"Don\u0027t get stuck on it because it\u0027s in every cell."},{"Start":"03:10.715 ","End":"03:12.500","Text":"Osmotic pressure."},{"Start":"03:12.500 ","End":"03:15.020","Text":"This is the symbol for osmotic pressure."},{"Start":"03:15.020 ","End":"03:22.190","Text":"This can be defined as the measure of force necessary to resist water movement."},{"Start":"03:22.190 ","End":"03:23.750","Text":"Again, if we look here,"},{"Start":"03:23.750 ","End":"03:25.250","Text":"and we have pure water,"},{"Start":"03:25.250 ","End":"03:27.560","Text":"and then inside this tube,"},{"Start":"03:27.560 ","End":"03:29.180","Text":"we have a solution,"},{"Start":"03:29.180 ","End":"03:32.480","Text":"meaning lower concentration of water in the solutions,"},{"Start":"03:32.480 ","End":"03:35.540","Text":"and there\u0027s a semipermeable membrane here at the bottom,"},{"Start":"03:35.540 ","End":"03:38.180","Text":"you\u0027ll see water wanting to go into the tube."},{"Start":"03:38.180 ","End":"03:42.290","Text":"What happens is the height with the water mixing"},{"Start":"03:42.290 ","End":"03:46.700","Text":"in with the solution will go up because water has increased."},{"Start":"03:46.700 ","End":"03:52.010","Text":"This height is as a result of"},{"Start":"03:52.010 ","End":"03:55.160","Text":"the osmotic pressure that is"},{"Start":"03:55.160 ","End":"03:57.410","Text":"from the high concentration of water to"},{"Start":"03:57.410 ","End":"04:00.350","Text":"the low concentration of water because of this solution."},{"Start":"04:00.350 ","End":"04:03.830","Text":"Now here we talked about reverse osmosis."},{"Start":"04:03.830 ","End":"04:06.170","Text":"The idea is that there\u0027s a piston,"},{"Start":"04:06.170 ","End":"04:12.620","Text":"there\u0027s a physical element that\u0027s putting pressure on the liquid causing"},{"Start":"04:12.620 ","End":"04:21.050","Text":"water molecules to be pushed out of this tube in the semipermeable membrane region."},{"Start":"04:21.050 ","End":"04:28.355","Text":"It\u0027s resisting the natural water movement of going into the tube."},{"Start":"04:28.355 ","End":"04:34.820","Text":"So here this is applying osmotic pressure so that the water molecules leave and move from"},{"Start":"04:34.820 ","End":"04:41.645","Text":"the lower concentration of water in this tube out to the pure water solution."},{"Start":"04:41.645 ","End":"04:44.045","Text":"Now that we understand the idea of osmotic pressure,"},{"Start":"04:44.045 ","End":"04:47.360","Text":"osmotic pressure can be approximated by the Van\u0027t Hoff equation."},{"Start":"04:47.360 ","End":"04:49.855","Text":"What you see here is the equation."},{"Start":"04:49.855 ","End":"04:53.300","Text":"In this equation, R is the gas constant,"},{"Start":"04:53.300 ","End":"04:55.235","Text":"T is the absolute temperature,"},{"Start":"04:55.235 ","End":"04:59.015","Text":"and these both should be familiar to you from previous equations we had covered."},{"Start":"04:59.015 ","End":"05:00.845","Text":"Then you have a new symbol, the symbol i,"},{"Start":"05:00.845 ","End":"05:03.530","Text":"and that is the Van\u0027t Hoff factor."},{"Start":"05:03.530 ","End":"05:08.900","Text":"This is a measure of the extent to which the solutes dissociate into ionic species."},{"Start":"05:08.900 ","End":"05:11.015","Text":"If we talked about NaCl,"},{"Start":"05:11.015 ","End":"05:16.415","Text":"it\u0027s dissociating into 2 species."},{"Start":"05:16.415 ","End":"05:20.460","Text":"This would be 2 for sodium chloride."},{"Start":"05:20.460 ","End":"05:28.670","Text":"C, this symbol stands for molar concentration of the solute,"},{"Start":"05:28.670 ","End":"05:33.035","Text":"how many moles per solution there is, molar concentration."},{"Start":"05:33.035 ","End":"05:34.430","Text":"The term ic,"},{"Start":"05:34.430 ","End":"05:36.575","Text":"which is the combination of these 2,"},{"Start":"05:36.575 ","End":"05:39.560","Text":"is the osmolarity of the solution."},{"Start":"05:39.560 ","End":"05:46.235","Text":"It is the product of Hoff factor, i,"},{"Start":"05:46.235 ","End":"05:49.225","Text":"and the solute\u0027s molar concentration,"},{"Start":"05:49.225 ","End":"05:55.790","Text":"c. Let\u0027s explain this formula in a way that you understand it better using an example."},{"Start":"05:55.790 ","End":"05:57.740","Text":"Sodium chloride solution is NaCl."},{"Start":"05:57.740 ","End":"06:02.090","Text":"The solute dissociates into Na plus and Cl minus, sodium chloride ions,"},{"Start":"06:02.090 ","End":"06:06.710","Text":"doubling the number of solute particles to 2 because we had 1,"},{"Start":"06:06.710 ","End":"06:07.946","Text":"and now it\u0027s 2."},{"Start":"06:07.946 ","End":"06:09.230","Text":"It\u0027s doubling it by 2."},{"Start":"06:09.230 ","End":"06:11.300","Text":"If you have 4 sodium chlorides,"},{"Start":"06:11.300 ","End":"06:14.480","Text":"and they each break apart to their 2 ions,"},{"Start":"06:14.480 ","End":"06:17.180","Text":"it means you are going to have 4 sodium and 4 chlorides,"},{"Start":"06:17.180 ","End":"06:18.590","Text":"and it will result in 8,"},{"Start":"06:18.590 ","End":"06:23.150","Text":"so now you have 2 times the original amount,"},{"Start":"06:23.150 ","End":"06:25.210","Text":"so i equals 2."},{"Start":"06:25.210 ","End":"06:29.150","Text":"For all non-ionizing solutes, i equals 1."},{"Start":"06:29.150 ","End":"06:33.080","Text":"For solutes that don\u0027t break up into ions,"},{"Start":"06:33.080 ","End":"06:37.355","Text":"they state 1 molecule i equals 1."},{"Start":"06:37.355 ","End":"06:40.220","Text":"For solutions of several solutes, n,"},{"Start":"06:40.220 ","End":"06:42.276","Text":"number of solutes,"},{"Start":"06:42.276 ","End":"06:45.080","Text":"what this means, you take this part of the formula,"},{"Start":"06:45.080 ","End":"06:47.600","Text":"and then you refer to the n number of solutes,"},{"Start":"06:47.600 ","End":"06:49.985","Text":"and you add these up,"},{"Start":"06:49.985 ","End":"06:52.700","Text":"it\u0027s a sum of all these species,"},{"Start":"06:52.700 ","End":"06:55.995","Text":"and it is n times."},{"Start":"06:55.995 ","End":"06:58.160","Text":"You have the first species, the second, third,"},{"Start":"06:58.160 ","End":"07:02.404","Text":"and on and on until n number of species."},{"Start":"07:02.404 ","End":"07:08.060","Text":"So this is what is used to approximate osmotic pressure."},{"Start":"07:08.060 ","End":"07:13.175","Text":"With this, we completed both parts of the introduction to colligative properties,"},{"Start":"07:13.175 ","End":"07:15.965","Text":"and you should be able to define colligative properties,"},{"Start":"07:15.965 ","End":"07:17.900","Text":"understand osmosis, diffusion,"},{"Start":"07:17.900 ","End":"07:19.955","Text":"tonicity, and their function in solutions,"},{"Start":"07:19.955 ","End":"07:24.420","Text":"and establish the significance of these properties in organisms."}],"ID":28499},{"Watched":false,"Name":"Exercise 1","Duration":"42s","ChapterTopicVideoID":27416,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.150","Text":"Hi, there. Welcome to the topic of colligative properties."},{"Start":"00:03.150 ","End":"00:05.865","Text":"We\u0027re having an introduction to collegiate properties."},{"Start":"00:05.865 ","End":"00:07.875","Text":"Let\u0027s start with an exercise."},{"Start":"00:07.875 ","End":"00:11.880","Text":"List the 4 colligative properties and define collegiate."},{"Start":"00:11.880 ","End":"00:16.965","Text":"Solutes have all kinds alter certain physical properties of the solvent, water."},{"Start":"00:16.965 ","End":"00:22.020","Text":"Different solutes can alter the water, the solvent."},{"Start":"00:22.020 ","End":"00:26.655","Text":"These certain physical properties that can be altered are vapor pressure,"},{"Start":"00:26.655 ","End":"00:28.350","Text":"boiling point, melting point,"},{"Start":"00:28.350 ","End":"00:31.890","Text":"and the reverse freezing point, and osmotic pressure."},{"Start":"00:31.890 ","End":"00:33.630","Text":"As for the collegiate,"},{"Start":"00:33.630 ","End":"00:36.480","Text":"we said these are all called colligative properties"},{"Start":"00:36.480 ","End":"00:39.540","Text":"with colligative meaning tied together,"},{"Start":"00:39.540 ","End":"00:43.150","Text":"things that are bound together. Let\u0027s move on."}],"ID":28500},{"Watched":false,"Name":"Exercise 2","Duration":"3m 35s","ChapterTopicVideoID":27417,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.865","Text":"Welcome back to another exercise on colligative of properties."},{"Start":"00:02.865 ","End":"00:05.940","Text":"Which of the options is correct for each statement: A,"},{"Start":"00:05.940 ","End":"00:11.676","Text":"the concentration of water is higher/lower in solutions than in pure water; B,"},{"Start":"00:11.676 ","End":"00:14.790","Text":"the effect of solute concentrations on the colligative properties of water is"},{"Start":"00:14.790 ","End":"00:18.210","Text":"dependent/independent of the chemical properties of the solute;"},{"Start":"00:18.210 ","End":"00:20.070","Text":"C, the concentration depends on"},{"Start":"00:20.070 ","End":"00:24.660","Text":"the number/mass of solute particles in a given amount of water."},{"Start":"00:24.660 ","End":"00:28.440","Text":"D, water molecules tend to move from a region of"},{"Start":"00:28.440 ","End":"00:36.195","Text":"higher/lower water concentration to 1 of higher/lower water concentration."},{"Start":"00:36.195 ","End":"00:39.825","Text":"Starting with A,"},{"Start":"00:39.825 ","End":"00:42.740","Text":"the concentration of water is higher/lower in solutions than in pure water."},{"Start":"00:42.740 ","End":"00:45.920","Text":"We actually started with a statement saying something,"},{"Start":"00:45.920 ","End":"00:47.330","Text":"but before I just say that statement,"},{"Start":"00:47.330 ","End":"00:49.580","Text":"let\u0027s choose logic, in case you forget,"},{"Start":"00:49.580 ","End":"00:51.230","Text":"and you freeze,"},{"Start":"00:51.230 ","End":"00:52.910","Text":"and you get confused."},{"Start":"00:52.910 ","End":"00:58.145","Text":"A solution means there is a solvent and a solute."},{"Start":"00:58.145 ","End":"01:03.755","Text":"Pure water means there\u0027s just water."},{"Start":"01:03.755 ","End":"01:05.985","Text":"Now, in the case of a solution,"},{"Start":"01:05.985 ","End":"01:09.520","Text":"we\u0027ve talked about water being a solvent many times."},{"Start":"01:09.520 ","End":"01:14.795","Text":"So if you have an equal amount of liquid in 2 cups,"},{"Start":"01:14.795 ","End":"01:16.835","Text":"but in 1 of them,"},{"Start":"01:16.835 ","End":"01:21.950","Text":"it\u0027s split between molecules of solvent and solute and not necessarily 50/50."},{"Start":"01:21.950 ","End":"01:26.060","Text":"It can even be 3 molecules of solute and 97 solvent,"},{"Start":"01:26.060 ","End":"01:27.725","Text":"but here it\u0027s a 100 percent water."},{"Start":"01:27.725 ","End":"01:31.880","Text":"Then logically that means that the concentration of water,"},{"Start":"01:31.880 ","End":"01:37.395","Text":"the percent of water molecules in the pure water will be higher than in solutions."},{"Start":"01:37.395 ","End":"01:39.500","Text":"If we look at this sentence,"},{"Start":"01:39.500 ","End":"01:43.400","Text":"the concentration of water is higher/lower in solutions than in pure water,"},{"Start":"01:43.400 ","End":"01:47.790","Text":"then it is lower than in pure water."},{"Start":"01:47.790 ","End":"01:48.900","Text":"Let\u0027s move on to B, the effect of"},{"Start":"01:48.900 ","End":"01:51.290","Text":"the solute concentration on the colligative properties of water"},{"Start":"01:51.290 ","End":"01:55.130","Text":"is dependent/independent of the chemical properties of the solute."},{"Start":"01:55.130 ","End":"01:58.430","Text":"But we\u0027ve talked about the concentration of colligative of properties actually"},{"Start":"01:58.430 ","End":"02:03.245","Text":"depending on the number of molecules,"},{"Start":"02:03.245 ","End":"02:08.580","Text":"and the number of molecules is not actually a chemical property."},{"Start":"02:08.580 ","End":"02:13.050","Text":"So that would mean that it is not dependent on chemical properties."},{"Start":"02:13.050 ","End":"02:14.824","Text":"It is independent."},{"Start":"02:14.824 ","End":"02:17.360","Text":"So the effect of solute concentration on the colligative of properties of water"},{"Start":"02:17.360 ","End":"02:20.240","Text":"is independent of the chemical properties of the solutes."},{"Start":"02:20.240 ","End":"02:22.140","Text":"So this is out."},{"Start":"02:22.140 ","End":"02:24.110","Text":"C, the concentration depends on"},{"Start":"02:24.110 ","End":"02:27.905","Text":"the number/the mass of solute particles in a given amount of water."},{"Start":"02:27.905 ","End":"02:32.030","Text":"Again, we talked about an example with"},{"Start":"02:32.030 ","End":"02:38.150","Text":"sodium chloride splitting from 1 molecule in solution to 2."},{"Start":"02:38.150 ","End":"02:43.235","Text":"We said number. We didn\u0027t actually talk about mass."},{"Start":"02:43.235 ","End":"02:47.134","Text":"So we can then say then it\u0027s the number because"},{"Start":"02:47.134 ","End":"02:52.865","Text":"that is what is changing and affecting the concentration,"},{"Start":"02:52.865 ","End":"02:57.214","Text":"so the number of molecules that are in the solvent."},{"Start":"02:57.214 ","End":"03:00.050","Text":"This leaves us with the concentration depends on"},{"Start":"03:00.050 ","End":"03:03.290","Text":"the number of solute particles in a given amount of water."},{"Start":"03:03.290 ","End":"03:04.415","Text":"Last but not least,"},{"Start":"03:04.415 ","End":"03:06.770","Text":"we have water molecules tend to move from"},{"Start":"03:06.770 ","End":"03:12.785","Text":"a higher/lower water concentration to a higher/lower concentration."},{"Start":"03:12.785 ","End":"03:18.155","Text":"It will go from a higher to a lower water concentration."},{"Start":"03:18.155 ","End":"03:21.020","Text":"It will want to balance it out,"},{"Start":"03:21.020 ","End":"03:26.345","Text":"and therefore, we could talk about diffusion and osmosis."},{"Start":"03:26.345 ","End":"03:29.780","Text":"The correct statement is the water molecules tend"},{"Start":"03:29.780 ","End":"03:33.080","Text":"to move from higher to lower water concentration,"},{"Start":"03:33.080 ","End":"03:35.940","Text":"and there you have it."}],"ID":28501},{"Watched":false,"Name":"Exercise 3","Duration":"3m 7s","ChapterTopicVideoID":27408,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.440","Text":"Hello, welcome back to an exercise on colligative properties."},{"Start":"00:04.440 ","End":"00:07.845","Text":"Let\u0027s start with part 1, define osmotic pressure."},{"Start":"00:07.845 ","End":"00:10.860","Text":"Osmotic pressure can be defined as"},{"Start":"00:10.860 ","End":"00:14.850","Text":"the measure of force necessary to resist water movement."},{"Start":"00:14.850 ","End":"00:21.492","Text":"When 2 different aqueous solutions are separated by a semi-permeable membrane,"},{"Start":"00:21.492 ","End":"00:25.580","Text":"a membrane that only allows semi passage of"},{"Start":"00:25.580 ","End":"00:30.860","Text":"water molecules versus not allowing other molecules, water molecules diffusing,"},{"Start":"00:30.860 ","End":"00:36.740","Text":"transferring, moving from the region of higher water concentration"},{"Start":"00:36.740 ","End":"00:42.730","Text":"to the region of lower water concentration produce osmotic pressure."},{"Start":"00:42.730 ","End":"00:45.170","Text":"Basically the movement of"},{"Start":"00:45.170 ","End":"00:48.710","Text":"water molecules diffusing from higher concentration to lower concentration through"},{"Start":"00:48.710 ","End":"00:51.620","Text":"a semi-permeable membrane against semi-permeable membrane is"},{"Start":"00:51.620 ","End":"00:54.920","Text":"one that allows the passage of water but not solute molecules."},{"Start":"00:54.920 ","End":"00:58.370","Text":"That pressure of movement,"},{"Start":"00:58.370 ","End":"01:02.750","Text":"that directionality of the movement is what produces osmotic pressure."},{"Start":"01:02.750 ","End":"01:03.920","Text":"Osmotic pressure, think of it,"},{"Start":"01:03.920 ","End":"01:07.235","Text":"the pressure of osmosis on the membrane."},{"Start":"01:07.235 ","End":"01:11.310","Text":"Part 2, what are factors that affect osmotic pressure?"},{"Start":"01:11.310 ","End":"01:19.160","Text":"We introduced an equation that allows us to approximate and calculate osmotic pressure."},{"Start":"01:19.160 ","End":"01:23.030","Text":"These factors are what affect it."},{"Start":"01:23.030 ","End":"01:26.930","Text":"Osmotic pressure can be approximated by the van\u0027t Hoff equation,"},{"Start":"01:26.930 ","End":"01:28.895","Text":"I, which we see here."},{"Start":"01:28.895 ","End":"01:30.722","Text":"In this equation,"},{"Start":"01:30.722 ","End":"01:32.420","Text":"R is the gas constant,"},{"Start":"01:32.420 ","End":"01:34.955","Text":"T is the absolute temperature,"},{"Start":"01:34.955 ","End":"01:38.392","Text":"and these are things that we will know from the conditions of the environment"},{"Start":"01:38.392 ","End":"01:42.035","Text":"of the experiment of this situation of this system."},{"Start":"01:42.035 ","End":"01:46.155","Text":"Then we have i, which is a van\u0027t Hoff factor, lowercase i."},{"Start":"01:46.155 ","End":"01:49.400","Text":"This is a measure of the extent to which the solute"},{"Start":"01:49.400 ","End":"01:52.670","Text":"dissociated into 2 or more ionic species, like sodium chloride,"},{"Start":"01:52.670 ","End":"01:56.365","Text":"which dissociated into 2 ionic species,"},{"Start":"01:56.365 ","End":"01:59.825","Text":"sodium ion and chloride ion."},{"Start":"01:59.825 ","End":"02:04.730","Text":"Sodium chloride solutions of solute dissociates into Na+ and Cl-, these 2 ions,"},{"Start":"02:04.730 ","End":"02:07.730","Text":"doubling the number of solute particles i=2 because"},{"Start":"02:07.730 ","End":"02:11.000","Text":"from 1 solute molecule of sodium chloride,"},{"Start":"02:11.000 ","End":"02:12.605","Text":"we now have 2."},{"Start":"02:12.605 ","End":"02:15.170","Text":"For non-ionizing solutes,"},{"Start":"02:15.170 ","End":"02:16.880","Text":"solutes that don\u0027t ionize,"},{"Start":"02:16.880 ","End":"02:18.590","Text":"they don\u0027t turn into ions,"},{"Start":"02:18.590 ","End":"02:19.999","Text":"they don\u0027t separate,"},{"Start":"02:19.999 ","End":"02:24.110","Text":"the number of solute particles remains 1,"},{"Start":"02:24.110 ","End":"02:27.290","Text":"the entire molecule because it hasn\u0027t separated."},{"Start":"02:27.290 ","End":"02:33.640","Text":"Then we have lowercase c. This is molar concentration of the solute."},{"Start":"02:33.640 ","End":"02:36.610","Text":"Together, as you see here,"},{"Start":"02:36.610 ","End":"02:39.440","Text":"ic is the osmolarity of the solution."},{"Start":"02:39.440 ","End":"02:41.240","Text":"It is the product of the van\u0027t Hoff factor,"},{"Start":"02:41.240 ","End":"02:43.590","Text":"i, and a solute\u0027s molar concentration,"},{"Start":"02:43.590 ","End":"02:47.450","Text":"c. Basically the factors that affect osmotic pressure"},{"Start":"02:47.450 ","End":"02:52.640","Text":"are all these things that come together in this equation: the gas constant,"},{"Start":"02:52.640 ","End":"02:54.950","Text":"absolute temperature, and Hoff factor,"},{"Start":"02:54.950 ","End":"02:56.510","Text":"molar concentration of the solute."},{"Start":"02:56.510 ","End":"02:57.880","Text":"This product, ic,"},{"Start":"02:57.880 ","End":"03:01.280","Text":"the product of van\u0027t Hoff factor and a solute\u0027s molar concentration,"},{"Start":"03:01.280 ","End":"03:04.040","Text":"which is actually the osmolarity of the solution,"},{"Start":"03:04.040 ","End":"03:07.140","Text":"these affect osmotic pressure."}],"ID":28502},{"Watched":false,"Name":"Osmolarity , Solutes and the Cell Part 1","Duration":"8m 35s","ChapterTopicVideoID":27409,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.110 ","End":"00:03.510","Text":"Hey there, in this section we\u0027ll be talking about osmolarity:"},{"Start":"00:03.510 ","End":"00:06.360","Text":"solutes and the cell within colligative properties."},{"Start":"00:06.360 ","End":"00:07.740","Text":"At the end of this section,"},{"Start":"00:07.740 ","End":"00:10.110","Text":"you\u0027ll be able to define osmosis,"},{"Start":"00:10.110 ","End":"00:12.465","Text":"hypertonic and hypotonic solutions,"},{"Start":"00:12.465 ","End":"00:16.560","Text":"understand osmosis and its significance to cell structure and function,"},{"Start":"00:16.560 ","End":"00:20.070","Text":"and understand osmotic lysis and how organisms prevent this."},{"Start":"00:20.070 ","End":"00:23.310","Text":"Now, we\u0027ll split this section into 2 parts."},{"Start":"00:23.310 ","End":"00:26.430","Text":"The first part, we will specifically go"},{"Start":"00:26.430 ","End":"00:29.640","Text":"over defining osmosis and hypertonic and hypotonic solutions,"},{"Start":"00:29.640 ","End":"00:33.570","Text":"and understand osmosis and its significance to cell structure and function."},{"Start":"00:33.570 ","End":"00:38.660","Text":"We introduced osmolarity in the previous section and now we\u0027re going to expand on this."},{"Start":"00:38.660 ","End":"00:40.390","Text":"Let\u0027s define some terms."},{"Start":"00:40.390 ","End":"00:42.980","Text":"Osmosis, this means water movement across"},{"Start":"00:42.980 ","End":"00:47.360","Text":"a semipermeable membrane driven by differences in osmotic pressure."},{"Start":"00:47.360 ","End":"00:49.460","Text":"When we talked about semipermeable membrane,"},{"Start":"00:49.460 ","End":"00:54.260","Text":"we mentioned this is a membrane that allows for water molecules"},{"Start":"00:54.260 ","End":"00:59.075","Text":"to pass through but limits the passage of various other molecules."},{"Start":"00:59.075 ","End":"01:02.330","Text":"This is an important factor in the life of most cells."},{"Start":"01:02.330 ","End":"01:09.705","Text":"Plasma membranes are more permeable to water than to most other small molecules, ions,"},{"Start":"01:09.705 ","End":"01:12.410","Text":"and macromolecules due to"},{"Start":"01:12.410 ","End":"01:16.570","Text":"protein channels in the membrane which are selectively permissive,"},{"Start":"01:16.570 ","End":"01:21.230","Text":"thus permit the passage of water and limit the passage of other things."},{"Start":"01:21.230 ","End":"01:23.975","Text":"Semipermeable membrane, as in,"},{"Start":"01:23.975 ","End":"01:26.920","Text":"a cell membrane, movement of water,"},{"Start":"01:26.920 ","End":"01:30.030","Text":"these molecules can pass through"},{"Start":"01:30.030 ","End":"01:33.740","Text":"the membrane from the outside of the cell to the inside of"},{"Start":"01:33.740 ","End":"01:41.105","Text":"cells yet salt cannot just pass through the membrane or other various molecules."},{"Start":"01:41.105 ","End":"01:44.090","Text":"These that are within stay within,"},{"Start":"01:44.090 ","End":"01:47.030","Text":"these that are outside stay outside,"},{"Start":"01:47.030 ","End":"01:52.015","Text":"but it is these water molecules that can move across the membrane."},{"Start":"01:52.015 ","End":"01:55.800","Text":"Now, this leads us to additional definitions."},{"Start":"01:55.800 ","End":"01:57.900","Text":"Isotonic solutions."},{"Start":"01:57.900 ","End":"02:04.220","Text":"Isotonic, these are solutions that are equal in osmolarity to that of a cell\u0027s cytosol."},{"Start":"02:04.220 ","End":"02:10.925","Text":"These are considered isotonic compared or relatively to the cell."},{"Start":"02:10.925 ","End":"02:13.850","Text":"Isotonic, this is"},{"Start":"02:13.850 ","End":"02:23.510","Text":"an equal osmolarity between the cell cytosol and the outside."},{"Start":"02:23.510 ","End":"02:26.255","Text":"Looking at, say,"},{"Start":"02:26.255 ","End":"02:29.525","Text":"the water outside of the cell versus inside of the cell,"},{"Start":"02:29.525 ","End":"02:33.670","Text":"it just continuously goes in and out because it\u0027s equal."},{"Start":"02:33.670 ","End":"02:39.335","Text":"A cell surrounded by an isotonic solution neither gains nor loses water."},{"Start":"02:39.335 ","End":"02:45.980","Text":"Now, this doesn\u0027t mean that there isn\u0027t water movement, there is,"},{"Start":"02:45.980 ","End":"02:51.620","Text":"but grand scale of things with regard to volume or molecules,"},{"Start":"02:51.620 ","End":"02:54.570","Text":"it remains somewhat stable,"},{"Start":"02:54.570 ","End":"02:59.900","Text":"constant, this dynamic stability of water in and out in equal ratio,"},{"Start":"02:59.900 ","End":"03:04.205","Text":"therefore, it doesn\u0027t gain or lose water."},{"Start":"03:04.205 ","End":"03:06.750","Text":"Next we have hypertonic solutions."},{"Start":"03:06.750 ","End":"03:07.935","Text":"We started with isotonic,"},{"Start":"03:07.935 ","End":"03:10.680","Text":"iso, and we said this is equal."},{"Start":"03:10.680 ","End":"03:12.855","Text":"Next we have hypertonic,"},{"Start":"03:12.855 ","End":"03:15.820","Text":"hyper, this should be familiar, hyper,"},{"Start":"03:15.820 ","End":"03:18.709","Text":"some with a lot of energy, an excess,"},{"Start":"03:18.709 ","End":"03:24.000","Text":"so hyper will be higher, excess."},{"Start":"03:24.200 ","End":"03:28.920","Text":"This gives us an indication on what hypertonic solutions are,"},{"Start":"03:28.920 ","End":"03:35.180","Text":"and these are solutions that have higher osmolarity than that of the cytosol."},{"Start":"03:35.180 ","End":"03:39.050","Text":"Because it has higher osmolarity than that of the cytosol,"},{"Start":"03:39.050 ","End":"03:43.820","Text":"meaning they have a higher concentration, the solution,"},{"Start":"03:43.820 ","End":"03:46.700","Text":"then the concentration in the cell,"},{"Start":"03:46.700 ","End":"03:49.840","Text":"for example, higher salt content,"},{"Start":"03:49.840 ","End":"03:55.550","Text":"then water will move from the cell outside of the cell to the solution surrounding"},{"Start":"03:55.550 ","End":"04:02.520","Text":"a cell in order to try to equalize the concentration of the solutions inside and outside."},{"Start":"04:02.520 ","End":"04:07.400","Text":"Therefore, you see water moves out of the cell and the cell shrinks."},{"Start":"04:07.400 ","End":"04:09.905","Text":"This is what we see happening in hypertonic,"},{"Start":"04:09.905 ","End":"04:14.975","Text":"water exits the cell to the surrounding."},{"Start":"04:14.975 ","End":"04:18.500","Text":"Isotonic, equal."},{"Start":"04:18.500 ","End":"04:20.975","Text":"Hyper, excess."},{"Start":"04:20.975 ","End":"04:23.449","Text":"Equal and out. Hyper, excess."},{"Start":"04:23.449 ","End":"04:27.540","Text":"You have water exiting the cell,"},{"Start":"04:27.540 ","End":"04:30.230","Text":"as mentioned, and hence the cell shrinks."},{"Start":"04:30.230 ","End":"04:33.530","Text":"Next we have hypotonic solutions."},{"Start":"04:33.530 ","End":"04:37.990","Text":"Hypo, the opposite of hyper,"},{"Start":"04:37.990 ","End":"04:43.100","Text":"having a reduced versus an excess."},{"Start":"04:43.100 ","End":"04:47.640","Text":"This is a solution with lower osmolarity than the cytosol."},{"Start":"04:47.640 ","End":"04:49.430","Text":"The surrounding solution, for example,"},{"Start":"04:49.430 ","End":"04:53.285","Text":"the cell cytosol has lower osmolarity,"},{"Start":"04:53.285 ","End":"05:00.050","Text":"meaning it has less particles versus solvent,"},{"Start":"05:00.050 ","End":"05:03.000","Text":"so less solute for solvent."},{"Start":"05:03.000 ","End":"05:09.065","Text":"Therefore, water will move from the surrounding solution"},{"Start":"05:09.065 ","End":"05:16.505","Text":"into the cell to try to equalize the higher osmolarity in the cell."},{"Start":"05:16.505 ","End":"05:20.210","Text":"Now, this water moves into the cell from"},{"Start":"05:20.210 ","End":"05:24.865","Text":"the surrounding hypotonic solution and thus the cell swells."},{"Start":"05:24.865 ","End":"05:28.080","Text":"Isotonic, you have equal entry, exit,"},{"Start":"05:28.080 ","End":"05:33.080","Text":"there isn\u0027t really a change in the water content of the cell."},{"Start":"05:33.080 ","End":"05:38.810","Text":"Hypertonic means the solution outside with higher osmolarity,"},{"Start":"05:38.810 ","End":"05:40.230","Text":"basically higher concentration,"},{"Start":"05:40.230 ","End":"05:44.000","Text":"so water from a lower concentrated area, which is the cell,"},{"Start":"05:44.000 ","End":"05:46.460","Text":"will move out to the higher concentration"},{"Start":"05:46.460 ","End":"05:49.940","Text":"of the solution surrounding the cell to try to equalize."},{"Start":"05:49.940 ","End":"05:53.000","Text":"When you have hypotonic solution surrounding the cell,"},{"Start":"05:53.000 ","End":"05:59.060","Text":"this is in comparison to the cytosol, the cell cytoplasm,"},{"Start":"05:59.060 ","End":"06:04.129","Text":"the cell liquid, then we have water entering the cell"},{"Start":"06:04.129 ","End":"06:10.160","Text":"because the cell is more concentrated than the hypotonic solution."},{"Start":"06:10.160 ","End":"06:13.250","Text":"If enough of the water,"},{"Start":"06:13.250 ","End":"06:17.390","Text":"or more correctly, too much water enters the cell,"},{"Start":"06:17.390 ","End":"06:20.930","Text":"it can result in the cell bursting,"},{"Start":"06:20.930 ","End":"06:26.210","Text":"puncturing, lysing, just like if you put too much air in a balloon, it can pop."},{"Start":"06:26.210 ","End":"06:31.345","Text":"We bring this together for a very common stock illustration,"},{"Start":"06:31.345 ","End":"06:33.920","Text":"you have water balance of a cell."},{"Start":"06:33.920 ","End":"06:36.935","Text":"We have hypotonic, isotonic, and hypertonic."},{"Start":"06:36.935 ","End":"06:40.685","Text":"Throwing that at us, isotonic green, equal."},{"Start":"06:40.685 ","End":"06:43.670","Text":"You see equal amounts of water move in and out,"},{"Start":"06:43.670 ","End":"06:49.210","Text":"the osmolarity of the outside versus the inside is equal,"},{"Start":"06:49.210 ","End":"06:51.770","Text":"if we talk about concentration, it\u0027s equal,"},{"Start":"06:51.770 ","End":"06:54.500","Text":"overall concentration are equal,"},{"Start":"06:54.500 ","End":"06:59.840","Text":"cell remains constant with regard to water content."},{"Start":"06:59.840 ","End":"07:03.140","Text":"Now, throwing it in a different order we just taught,"},{"Start":"07:03.140 ","End":"07:06.485","Text":"I\u0027m going to go now to hypotonic, hypotonic solution."},{"Start":"07:06.485 ","End":"07:12.905","Text":"This means the outside concentration is lower than the inside concentration of the cell,"},{"Start":"07:12.905 ","End":"07:19.295","Text":"meaning that the cell is more concentrated and therefore water moves into the cell."},{"Start":"07:19.295 ","End":"07:20.660","Text":"As you can see here,"},{"Start":"07:20.660 ","End":"07:24.886","Text":"the arrows of the water are moving from the outside of the cell into the cell"},{"Start":"07:24.886 ","End":"07:29.475","Text":"and the cell expands and can even result in a lysing,"},{"Start":"07:29.475 ","End":"07:31.439","Text":"in puncturing, in bursting."},{"Start":"07:31.439 ","End":"07:34.170","Text":"Now, let\u0027s go to hypertonic solution,"},{"Start":"07:34.170 ","End":"07:39.450","Text":"the third and final of the 3 water balance states of cells."},{"Start":"07:39.450 ","End":"07:43.240","Text":"Hypertonic, as we said hyper, like hyperactive."},{"Start":"07:43.240 ","End":"07:47.030","Text":"Excess hypertonic solution means the solution outside of"},{"Start":"07:47.030 ","End":"07:51.335","Text":"a cell has a higher concentration than the inside."},{"Start":"07:51.335 ","End":"07:55.670","Text":"Hypertonic, higher concentration than the inside."},{"Start":"07:55.670 ","End":"08:00.680","Text":"This results in water exiting the cell to the surrounding solution to"},{"Start":"08:00.680 ","End":"08:03.560","Text":"try to equalize the concentration so"},{"Start":"08:03.560 ","End":"08:06.785","Text":"that the higher concentration outside is by adding water,"},{"Start":"08:06.785 ","End":"08:14.050","Text":"becoming lower, more closer to the concentration of the cell."},{"Start":"08:14.050 ","End":"08:16.730","Text":"What happens is that, as water moves out from the cell,"},{"Start":"08:16.730 ","End":"08:21.095","Text":"it causes crenation or shriveling or shrinking of the cell."},{"Start":"08:21.095 ","End":"08:23.810","Text":"With this, we completed part 1 of osmolarity, solutes,"},{"Start":"08:23.810 ","End":"08:27.140","Text":"and the cell and you should be able to define osmosis, hypertonic,"},{"Start":"08:27.140 ","End":"08:30.170","Text":"and hypotonic solutions and understand osmosis and"},{"Start":"08:30.170 ","End":"08:35.770","Text":"its significance to cell structure and function. Let\u0027s move on to part 2."}],"ID":28503},{"Watched":false,"Name":"Osmolarity , Solutes and the Cell Part 2","Duration":"11m 10s","ChapterTopicVideoID":27410,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.520","Text":"Hi. Welcome back to osmolarity,"},{"Start":"00:02.520 ","End":"00:04.829","Text":"solutes and the cell with inclusive properties."},{"Start":"00:04.829 ","End":"00:10.040","Text":"We are in Part 2 of this and within and by the end of the section you should be"},{"Start":"00:10.040 ","End":"00:12.540","Text":"able to understand osmosis and its significance to"},{"Start":"00:12.540 ","End":"00:15.750","Text":"cell structure and function and describe turgor pressure."},{"Start":"00:15.750 ","End":"00:18.360","Text":"Let\u0027s move to another term, again,"},{"Start":"00:18.360 ","End":"00:23.420","Text":"using the term osmosis, osmolarity, osmotic pressure."},{"Start":"00:23.420 ","End":"00:26.730","Text":"We mentioned this term in passing, now let\u0027s break it through."},{"Start":"00:26.730 ","End":"00:33.870","Text":"This is what is used as the symbol for osmotic pressures Pi and osmotic pressure which we"},{"Start":"00:33.870 ","End":"00:37.350","Text":"defined in a previous section as the measure"},{"Start":"00:37.350 ","End":"00:41.310","Text":"of force necessary to resist water movements."},{"Start":"00:41.310 ","End":"00:46.910","Text":"As you could see here you have a cell and the membrane."},{"Start":"00:46.910 ","End":"00:50.990","Text":"The membrane in essence creates a force,"},{"Start":"00:50.990 ","End":"00:56.180","Text":"a limiting force as to the ability of water to move."},{"Start":"00:56.180 ","End":"00:59.780","Text":"In their natural environment cells generally contain"},{"Start":"00:59.780 ","End":"01:04.160","Text":"higher concentrations of biomolecules and ions even their surroundings,"},{"Start":"01:04.160 ","End":"01:09.335","Text":"meaning water would enter the cell."},{"Start":"01:09.335 ","End":"01:14.225","Text":"The osmotic pressure difference thus drives water into cells."},{"Start":"01:14.225 ","End":"01:18.785","Text":"If the cell contains higher concentrations of biomolecules water will"},{"Start":"01:18.785 ","End":"01:24.290","Text":"enter the cell unless this inward movement of water is counterbalanced,"},{"Start":"01:24.290 ","End":"01:29.420","Text":"the plasma membrane would expand until the cell eventually bursts, osmotic lysis."},{"Start":"01:29.420 ","End":"01:34.850","Text":"If you remember, we saw that here you have osmotic lysis."},{"Start":"01:34.850 ","End":"01:38.720","Text":"This is what you\u0027re seeing. This represents lysis."},{"Start":"01:38.720 ","End":"01:40.010","Text":"The cell is bursting."},{"Start":"01:40.010 ","End":"01:41.660","Text":"You saw this also here."},{"Start":"01:41.660 ","End":"01:46.490","Text":"This represents a cell bursting popping open."},{"Start":"01:46.490 ","End":"01:51.950","Text":"Several mechanisms have evolved to prevent this catastrophe from occurring."},{"Start":"01:51.950 ","End":"01:54.020","Text":"In bacteria and plants,"},{"Start":"01:54.020 ","End":"02:00.785","Text":"the plasma membrane is surrounded by a non expandable cell wall,"},{"Start":"02:00.785 ","End":"02:05.120","Text":"which is rigid enough as well as strong enough"},{"Start":"02:05.120 ","End":"02:10.039","Text":"to resist the osmotic pressure which prevents osmotic lysis."},{"Start":"02:10.039 ","End":"02:16.070","Text":"Certain freshwater protists that live in a highly hypertonic medium."},{"Start":"02:16.070 ","End":"02:19.400","Text":"This fresh water, is not very concentrated."},{"Start":"02:19.400 ","End":"02:22.880","Text":"It\u0027s not like seawater that has salt, have an organelle,"},{"Start":"02:22.880 ","End":"02:28.975","Text":"a contractile vacuole that pumps water out of the cell."},{"Start":"02:28.975 ","End":"02:33.270","Text":"This contractile vacuole mean contraction."},{"Start":"02:33.270 ","End":"02:38.645","Text":"When you\u0027re contracting something it creates pressure for something to move out."},{"Start":"02:38.645 ","End":"02:40.310","Text":"I guess if you think of a balloon again,"},{"Start":"02:40.310 ","End":"02:42.755","Text":"let\u0027s say you put water in a balloon."},{"Start":"02:42.755 ","End":"02:46.520","Text":"If you squeeze the balloon, water, this pressure,"},{"Start":"02:46.520 ","End":"02:49.010","Text":"this contracting of the balloon,"},{"Start":"02:49.010 ","End":"02:55.075","Text":"will push the water out through the hole because of the pressure."},{"Start":"02:55.075 ","End":"03:01.150","Text":"Certain freshwater protists in hypotonic medium this fresh water, yeah,"},{"Start":"03:01.150 ","End":"03:04.670","Text":"have an organelle, the contractile vacuole that pumps water out"},{"Start":"03:04.670 ","End":"03:08.240","Text":"of the cell and that is what helps them to prevent."},{"Start":"03:08.240 ","End":"03:11.570","Text":"Now, in case you weren\u0027t sure what protists are,"},{"Start":"03:11.570 ","End":"03:13.100","Text":"there is an entire kingdom of"},{"Start":"03:13.100 ","End":"03:17.645","Text":"unseen or simply unrecognized organisms lurking in bodies of water."},{"Start":"03:17.645 ","End":"03:22.820","Text":"The kingdom is Protista and it represents an extremely diverse group of organisms,"},{"Start":"03:22.820 ","End":"03:25.010","Text":"many of which are found in freshwater environments."},{"Start":"03:25.010 ","End":"03:27.350","Text":"A large number of protists are microscopic,"},{"Start":"03:27.350 ","End":"03:30.560","Text":"however, various forms of algae are protists as well."},{"Start":"03:30.560 ","End":"03:34.475","Text":"Protists are mainly unicellular organisms that are also eukaryotic."},{"Start":"03:34.475 ","End":"03:37.760","Text":"Though they\u0027re tiny, they are complex."},{"Start":"03:37.760 ","End":"03:43.650","Text":"A reminder, a unicellular organism indicates that the organism is made of a single cell."},{"Start":"03:43.940 ","End":"03:46.720","Text":"That cell is eukaryotic,"},{"Start":"03:46.720 ","End":"03:50.540","Text":"meaning that it contains a nucleus as well as a plethora of organelles"},{"Start":"03:50.540 ","End":"03:54.565","Text":"with important jobs helping the cells run smoothly."},{"Start":"03:54.565 ","End":"03:58.880","Text":"In multi-cellular animals, blood plasma and interstitial fluid,"},{"Start":"03:58.880 ","End":"04:01.670","Text":"that\u0027s just the cellular fluid of tissues are maintained at"},{"Start":"04:01.670 ","End":"04:05.525","Text":"an osmolarity close to that of the cytosol and this helps"},{"Start":"04:05.525 ","End":"04:14.270","Text":"maintain this equal concentrations where there isn\u0027t the risk of this osmotic lysis."},{"Start":"04:14.270 ","End":"04:17.480","Text":"Now the high concentration, for example,"},{"Start":"04:17.480 ","End":"04:24.575","Text":"on an albumin and other proteins and blood plasma contributes to its osmolarity."},{"Start":"04:24.575 ","End":"04:28.820","Text":"There are certain things that are in the plasma and"},{"Start":"04:28.820 ","End":"04:35.120","Text":"the interstitial fluid that maintain this osmolarity that otherwise we said,"},{"Start":"04:35.120 ","End":"04:39.725","Text":"is generally higher in the cell than other surrounding solutions."},{"Start":"04:39.725 ","End":"04:44.270","Text":"Cells also pump out sodium and other ions into"},{"Start":"04:44.270 ","End":"04:48.950","Text":"the interstitial fluid to stay in osmotic balance with their surroundings."},{"Start":"04:48.950 ","End":"04:52.715","Text":"There is also this active functioning of pumping out"},{"Start":"04:52.715 ","End":"04:59.105","Text":"ions to the interstitial fluid to then keep this osmotic balance."},{"Start":"04:59.105 ","End":"05:05.605","Text":"Now an important concept to understand when dealing with osmolarity in"},{"Start":"05:05.605 ","End":"05:09.050","Text":"solutions is that the effect of solutes on"},{"Start":"05:09.050 ","End":"05:14.180","Text":"osmolarity depends on the number of dissolved particles not their mass."},{"Start":"05:14.180 ","End":"05:17.000","Text":"Macromolecules such as proteins, nucleic acids,"},{"Start":"05:17.000 ","End":"05:20.480","Text":"polysaccharides have far less effect on osmolarity of"},{"Start":"05:20.480 ","End":"05:25.250","Text":"a solution that would an equal mass of their monomeric components."},{"Start":"05:25.250 ","End":"05:26.945","Text":"What does this mean?"},{"Start":"05:26.945 ","End":"05:33.470","Text":"Storing fuel as polysaccharides such as starch or glycogen rather than as glucose,"},{"Start":"05:33.470 ","End":"05:38.255","Text":"remember poly is many rather than as glucose or other simple sugars,"},{"Start":"05:38.255 ","End":"05:43.750","Text":"avoids an enormous increase in osmotic pressure in the cell,"},{"Start":"05:43.750 ","End":"05:45.810","Text":"in the storage cell."},{"Start":"05:45.810 ","End":"05:50.210","Text":"1 gram of a polysaccharide composed of 1,000 glucose units has"},{"Start":"05:50.210 ","End":"05:56.575","Text":"the same effect on osmolarity as 1 milligram glucose."},{"Start":"05:56.575 ","End":"06:00.980","Text":"Additionally utilization of osmotic pressure for biological function as seen in the case"},{"Start":"06:00.980 ","End":"06:05.260","Text":"of plants which use osmotic pressure to achieve mechanical rigidity."},{"Start":"06:05.260 ","End":"06:10.640","Text":"The very high solute concentration in the plant cell vacuole draws water into"},{"Start":"06:10.640 ","End":"06:16.210","Text":"the cell while the non expandable rigid cell wall prevents expansion."},{"Start":"06:16.210 ","End":"06:19.310","Text":"A vacuole, as you can see here,"},{"Start":"06:19.310 ","End":"06:22.640","Text":"is a membrane bound organelle"},{"Start":"06:22.640 ","End":"06:26.059","Text":"which is present in plant and fungal cells and some protists,"},{"Start":"06:26.059 ","End":"06:28.040","Text":"animal and bacterial cells."},{"Start":"06:28.040 ","End":"06:34.010","Text":"This can be plants or some bacterial or fungal cells, etc."},{"Start":"06:34.010 ","End":"06:38.215","Text":"Now vacuoles are essentially enclosed compartments,"},{"Start":"06:38.215 ","End":"06:45.080","Text":"see this, which are filled with water containing inorganic and organic molecules."},{"Start":"06:45.080 ","End":"06:47.450","Text":"In animal cells vacuoles are generally small"},{"Start":"06:47.450 ","End":"06:49.985","Text":"and helps cluster and helps get rid of waste products."},{"Start":"06:49.985 ","End":"06:54.260","Text":"Sometimes the waste product is water and therefore a vacuole would have"},{"Start":"06:54.260 ","End":"06:59.690","Text":"had its function to maintain the balance of water inside and outside the cell."},{"Start":"06:59.690 ","End":"07:01.250","Text":"In plant cells, for example,"},{"Start":"07:01.250 ","End":"07:05.135","Text":"a vacuole helps maintain water balance."},{"Start":"07:05.135 ","End":"07:08.210","Text":"Interestingly, sometimes a single vacuole can take up most of"},{"Start":"07:08.210 ","End":"07:11.450","Text":"the interior space of the plant cell, as you see here."},{"Start":"07:11.450 ","End":"07:13.400","Text":"When you have a case of isotonic,"},{"Start":"07:13.400 ","End":"07:15.605","Text":"again going back to terms we\u0027ve covered before,"},{"Start":"07:15.605 ","End":"07:18.290","Text":"in a plant cell with the cell wall,"},{"Start":"07:18.290 ","End":"07:20.450","Text":"you have entry and exit of water."},{"Start":"07:20.450 ","End":"07:23.000","Text":"Here it\u0027s equal isotonic, entering,"},{"Start":"07:23.000 ","End":"07:26.930","Text":"exiting here you have hypotonic concentration of"},{"Start":"07:26.930 ","End":"07:30.950","Text":"the surrounding of the cell therefore water enters the cell and the vacuole"},{"Start":"07:30.950 ","End":"07:34.670","Text":"expands and can be an example of that case where we"},{"Start":"07:34.670 ","End":"07:39.050","Text":"mentioned that the vacuole can take up most of the interior space of the plant cell."},{"Start":"07:39.050 ","End":"07:42.320","Text":"When you have hypertonic solution surrounding the cell,"},{"Start":"07:42.320 ","End":"07:44.810","Text":"it means that the concentration is higher outside,"},{"Start":"07:44.810 ","End":"07:47.480","Text":"the osmotic pressure outside is higher and therefore"},{"Start":"07:47.480 ","End":"07:50.735","Text":"water will exit the cell to try to balance out."},{"Start":"07:50.735 ","End":"07:54.290","Text":"You have here the arrows are equal for water"},{"Start":"07:54.290 ","End":"07:58.025","Text":"entering and exiting the cell and here you have for the hypertonic,"},{"Start":"07:58.025 ","End":"08:00.860","Text":"the arrow of water exiting the cell is way"},{"Start":"08:00.860 ","End":"08:04.460","Text":"greater than that of entering the cell and therefore it shrivels."},{"Start":"08:04.460 ","End":"08:08.645","Text":"You have this vacuole and the content of the cell shriveling while"},{"Start":"08:08.645 ","End":"08:13.220","Text":"the plant cell wall maintains the plant cell,"},{"Start":"08:13.220 ","End":"08:17.025","Text":"actually somewhat remaining the same in shape."},{"Start":"08:17.025 ","End":"08:19.925","Text":"With the hypotonic, you have more water"},{"Start":"08:19.925 ","End":"08:23.420","Text":"entering the cell than exiting the vacuole is expanding,"},{"Start":"08:23.420 ","End":"08:27.155","Text":"takes up almost the entire cell and the plant cell wall is"},{"Start":"08:27.155 ","End":"08:31.290","Text":"what keeps it rigid and doesn\u0027t allow it to burst."},{"Start":"08:31.290 ","End":"08:35.100","Text":"This results in increased turgor pressure."},{"Start":"08:35.100 ","End":"08:38.205","Text":"An increase in the pressure exerted against the cell wall which"},{"Start":"08:38.205 ","End":"08:41.930","Text":"stiffens the cell and the tissue and the plant body."},{"Start":"08:41.930 ","End":"08:44.135","Text":"If we see here we have turgor pressure,"},{"Start":"08:44.135 ","End":"08:45.844","Text":"you have water entering."},{"Start":"08:45.844 ","End":"08:47.015","Text":"This is normal."},{"Start":"08:47.015 ","End":"08:48.875","Text":"Here we have the vacuole."},{"Start":"08:48.875 ","End":"08:51.890","Text":"Water fills it up, some plump."},{"Start":"08:51.890 ","End":"08:56.090","Text":"Here you have water leaving the cell more"},{"Start":"08:56.090 ","End":"09:01.160","Text":"than it\u0027s entering and this vacuole becomes flaccid."},{"Start":"09:01.160 ","End":"09:04.010","Text":"It shrivels, it shrinks,"},{"Start":"09:04.010 ","End":"09:11.495","Text":"and if water releases leaves at higher amounts and it really shrivels."},{"Start":"09:11.495 ","End":"09:14.600","Text":"You see that there are empty spots."},{"Start":"09:14.600 ","End":"09:16.100","Text":"It\u0027s considered to be plasma lysed."},{"Start":"09:16.100 ","End":"09:20.030","Text":"What you see is here this plant has shriveled,"},{"Start":"09:20.030 ","End":"09:22.610","Text":"The turgor pressure of it has reduced."},{"Start":"09:22.610 ","End":"09:28.835","Text":"There has been water exiting and you have this sad looking plant."},{"Start":"09:28.835 ","End":"09:30.650","Text":"Generally turgor pressure caused by"},{"Start":"09:30.650 ","End":"09:33.680","Text":"the osmotic flow of water and occurs in plants, fungi,"},{"Start":"09:33.680 ","End":"09:38.850","Text":"and bacteria, the phenomena is also observed in protists that have cell walls."},{"Start":"09:38.850 ","End":"09:41.555","Text":"This system is not seen in animal cells."},{"Start":"09:41.555 ","End":"09:44.570","Text":"To reiterate turgor pressure is the force within"},{"Start":"09:44.570 ","End":"09:48.180","Text":"the cell that pushes the plasma membrane against the cell wall."},{"Start":"09:48.180 ","End":"09:52.040","Text":"Is also called hydrostatic pressure."},{"Start":"09:52.040 ","End":"09:57.560","Text":"It\u0027s hydro, water, hydrostatic pressure."},{"Start":"09:57.560 ","End":"10:03.650","Text":"This is the pressure that is exerted against the cell wall,"},{"Start":"10:03.650 ","End":"10:07.325","Text":"which exists in plants and other organisms."},{"Start":"10:07.325 ","End":"10:13.760","Text":"Hydrostatic pressure is a synonym for turgor pressure."},{"Start":"10:13.760 ","End":"10:19.340","Text":"Furthermore, turgor is what pushes or what makes living plant tissue rigid."},{"Start":"10:19.340 ","End":"10:23.240","Text":"Loss of turgor resulting from the loss of water from plant cells"},{"Start":"10:23.240 ","End":"10:28.400","Text":"causes flowers and leaves to wilt when there\u0027s wilts, for example,"},{"Start":"10:28.400 ","End":"10:31.085","Text":"it is because loss of water resulted in"},{"Start":"10:31.085 ","End":"10:34.160","Text":"reduced turgor pressure and thus shrinking of the cells of"},{"Start":"10:34.160 ","End":"10:41.045","Text":"the lettuce therefore shrinking of the leaves as you see in this plant."},{"Start":"10:41.045 ","End":"10:44.435","Text":"At this point we had completed Part 2 of osmolarity,"},{"Start":"10:44.435 ","End":"10:46.280","Text":"solutes and the cell."},{"Start":"10:46.280 ","End":"10:50.795","Text":"We should be able to understand and describe osmosis."},{"Start":"10:50.795 ","End":"10:54.680","Text":"It\u0027s significant to cell structure and function and define turgor pressure."},{"Start":"10:54.680 ","End":"11:00.170","Text":"Stepping back after the combination of both sections we should be able to define osmosis,"},{"Start":"11:00.170 ","End":"11:04.640","Text":"hypertonic and hypotonic solutions and understand osmosis,"},{"Start":"11:04.640 ","End":"11:09.930","Text":"its significance and osmotic lysis and how organisms prevent this."}],"ID":28504},{"Watched":false,"Name":"Exercise 4","Duration":"1m 21s","ChapterTopicVideoID":27411,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.090","Text":"Hey there. Welcome to exercise covering osmolarity,"},{"Start":"00:03.090 ","End":"00:06.495","Text":"solutes and the cell within colligative properties of water."},{"Start":"00:06.495 ","End":"00:09.000","Text":"Define osmosis and osmotic pressure."},{"Start":"00:09.000 ","End":"00:12.570","Text":"Osmosis is the term that describes water movement across"},{"Start":"00:12.570 ","End":"00:18.132","Text":"a semipermeable membrane driven by differences in osmotic pressure,"},{"Start":"00:18.132 ","End":"00:22.260","Text":"so when we through both terms at the same time."},{"Start":"00:22.260 ","End":"00:26.220","Text":"It is an important factor in the life of most cells."},{"Start":"00:26.220 ","End":"00:31.649","Text":"Plasma membranes are more permeable to water than to most other small molecules, ions,"},{"Start":"00:31.649 ","End":"00:34.350","Text":"and macromolecules due to protein channels"},{"Start":"00:34.350 ","End":"00:37.530","Text":"in the membrane which are selectively permissive,"},{"Start":"00:37.530 ","End":"00:42.120","Text":"thus permit the passage of water and limit the passage of the rest."},{"Start":"00:42.120 ","End":"00:47.690","Text":"Osmosis is the term that describes this water movement across the semipermeable membrane."},{"Start":"00:47.690 ","End":"00:50.090","Text":"While osmotic pressure, with the symbol Pi,"},{"Start":"00:50.090 ","End":"00:56.104","Text":"can be defined as the measure of force necessary to resist water movement."},{"Start":"00:56.104 ","End":"00:59.420","Text":"When you have water moving outside the cell,"},{"Start":"00:59.420 ","End":"01:03.335","Text":"there could be osmotic pressure on the membrane itself."},{"Start":"01:03.335 ","End":"01:07.265","Text":"This pressure of the movement moving through it."},{"Start":"01:07.265 ","End":"01:10.430","Text":"Or when you have movement into the cell and the cell is"},{"Start":"01:10.430 ","End":"01:14.200","Text":"filled with water at swells and it keeps on swelling and swelling,"},{"Start":"01:14.200 ","End":"01:20.130","Text":"there is a lot of osmotic pressure on the membrane and it can result in lysis."}],"ID":28505},{"Watched":false,"Name":"Exercise 5","Duration":"2m 14s","ChapterTopicVideoID":27412,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.600","Text":"Hi there. Let\u0027s see what we learned in this section of osmolarity,"},{"Start":"00:03.600 ","End":"00:07.140","Text":"solutes, and the cell and collegiate properties of water."},{"Start":"00:07.140 ","End":"00:10.650","Text":"What are the three terms that illustrate the concentration of"},{"Start":"00:10.650 ","End":"00:15.285","Text":"a solution relative to the concentration of a cell?"},{"Start":"00:15.285 ","End":"00:18.720","Text":"So the three terms that illustrate"},{"Start":"00:18.720 ","End":"00:24.400","Text":"concentration of a solution relative to the concentration of a cell."},{"Start":"00:24.530 ","End":"00:29.105","Text":"One, isotonic solutions."},{"Start":"00:29.105 ","End":"00:34.490","Text":"These are solutions that are equal in osmolarity to that of a cell\u0027s cytosol."},{"Start":"00:34.490 ","End":"00:38.300","Text":"A cell surrounded by an isotonic solution neither gains nor loses"},{"Start":"00:38.300 ","End":"00:42.575","Text":"water because there\u0027s equal movement of water in and out of the cell."},{"Start":"00:42.575 ","End":"00:49.160","Text":"Hypertonic solutions are ones that have higher osmolarity than that of the cytosol,"},{"Start":"00:49.160 ","End":"00:53.750","Text":"resulting in water moving out of the cell and thus"},{"Start":"00:53.750 ","End":"00:58.280","Text":"the cell shrinks because the solution on the outside is more concentrated."},{"Start":"00:58.280 ","End":"01:02.495","Text":"Higher osmolarity, so water moves through on the cell to"},{"Start":"01:02.495 ","End":"01:07.715","Text":"the surrounding environment and therefore the cell shrinks."},{"Start":"01:07.715 ","End":"01:10.520","Text":"Then we have the hypotonic solutions."},{"Start":"01:10.520 ","End":"01:12.725","Text":"These are the opposite from the hyper,"},{"Start":"01:12.725 ","End":"01:16.925","Text":"and these are solutions with lower osmolarity than the cytosol,"},{"Start":"01:16.925 ","End":"01:21.845","Text":"resulting in water moving into the cell and the cell swells,"},{"Start":"01:21.845 ","End":"01:26.080","Text":"it expands, it can even result in bursting."},{"Start":"01:26.080 ","End":"01:28.380","Text":"Here you see that three cases."},{"Start":"01:28.380 ","End":"01:34.865","Text":"Isotonic have equal water moving in and out."},{"Start":"01:34.865 ","End":"01:39.680","Text":"Hypertonic, where it is more concentrated in the solution surrounding the cell,"},{"Start":"01:39.680 ","End":"01:42.139","Text":"therefore water exits the cell."},{"Start":"01:42.139 ","End":"01:44.570","Text":"This is concentrated and the cell shrivels,"},{"Start":"01:44.570 ","End":"01:50.590","Text":"and then hypotonic where there is a higher concentration inside the cell."},{"Start":"01:50.590 ","End":"01:56.495","Text":"Meaning lower osmolarity in its surrounding therefore water enters the cell and it"},{"Start":"01:56.495 ","End":"02:03.470","Text":"expands or swells and can even expand to the point where it is lysed,"},{"Start":"02:03.470 ","End":"02:05.854","Text":"it bursts, osmotic lysis."},{"Start":"02:05.854 ","End":"02:09.965","Text":"We also showed a couple of different illustrations in the lesson."},{"Start":"02:09.965 ","End":"02:11.210","Text":"If this is unclear,"},{"Start":"02:11.210 ","End":"02:15.090","Text":"I suggest go back and look at some of them."}],"ID":28506},{"Watched":false,"Name":"Exercise 6","Duration":"3m 7s","ChapterTopicVideoID":27413,"CourseChapterTopicPlaylistID":272573,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.720","Text":"Hi. We\u0027re covering another exercise in osmolarity,"},{"Start":"00:03.720 ","End":"00:05.865","Text":"solutes and the cell."},{"Start":"00:05.865 ","End":"00:08.550","Text":"What causes osmotic lysis of cells and how do"},{"Start":"00:08.550 ","End":"00:11.279","Text":"organisms and cells prevent this from occurring?"},{"Start":"00:11.279 ","End":"00:12.570","Text":"In their natural environment,"},{"Start":"00:12.570 ","End":"00:14.700","Text":"cells generally contain higher concentrations of"},{"Start":"00:14.700 ","End":"00:17.220","Text":"biomolecules and ions than their surroundings."},{"Start":"00:17.220 ","End":"00:22.500","Text":"The osmotic pressure difference thus drives water into cells,"},{"Start":"00:22.500 ","End":"00:24.630","Text":"meaning the cells will expand."},{"Start":"00:24.630 ","End":"00:28.620","Text":"Now unless this inward movement of water is counterbalanced,"},{"Start":"00:28.620 ","End":"00:33.270","Text":"the plasma membrane would expand until the cell eventually bursts."},{"Start":"00:33.270 ","End":"00:37.180","Text":"This is what we call osmotic lysis."},{"Start":"00:37.180 ","End":"00:40.925","Text":"Several mechanisms have evolved to prevent this disaster from occurring,"},{"Start":"00:40.925 ","End":"00:42.950","Text":"including in bacteria and plants, for example,"},{"Start":"00:42.950 ","End":"00:47.300","Text":"the plasma membrane is surrounded by a non expandable cell wall"},{"Start":"00:47.300 ","End":"00:51.770","Text":"which is rigid enough as well as strong enough to resist osmotic pressure."},{"Start":"00:51.770 ","End":"00:54.095","Text":"It is actually like a wall."},{"Start":"00:54.095 ","End":"00:56.900","Text":"Even though the water is pushing against it,"},{"Start":"00:56.900 ","End":"00:58.010","Text":"it cannot break through."},{"Start":"00:58.010 ","End":"01:01.175","Text":"If you are pushing up against the wall of your house,"},{"Start":"01:01.175 ","End":"01:05.090","Text":"unless you\u0027re the Hulk, you cannot push and break through that wall."},{"Start":"01:05.090 ","End":"01:07.160","Text":"It limits and stops you."},{"Start":"01:07.160 ","End":"01:13.879","Text":"This is 1 mechanism that bacteria and plants have and it is this cell wall."},{"Start":"01:13.879 ","End":"01:18.605","Text":"Another example, we mentioned, certain freshwater protists."},{"Start":"01:18.605 ","End":"01:24.650","Text":"These are organisms that it\u0027d be microscopic that live in water."},{"Start":"01:24.650 ","End":"01:28.265","Text":"A very general inclusive term."},{"Start":"01:28.265 ","End":"01:31.460","Text":"These certain freshwater protist that live in"},{"Start":"01:31.460 ","End":"01:35.180","Text":"highly hypotonic medium like freshwater, hypotonic,"},{"Start":"01:35.180 ","End":"01:38.450","Text":"not like saltwater, have an organelle called the"},{"Start":"01:38.450 ","End":"01:43.070","Text":"contractile vacuole that pumps water out of the cell."},{"Start":"01:43.070 ","End":"01:48.890","Text":"It literally physically contracts and pumps water out of the cell and thus,"},{"Start":"01:48.890 ","End":"01:52.325","Text":"the cell doesn\u0027t expand to the point where it burst."},{"Start":"01:52.325 ","End":"01:58.189","Text":"Another mechanism is in multicellular animals where blood plasma and interstitial fluid,"},{"Start":"01:58.189 ","End":"01:59.660","Text":"that is between the tissues,"},{"Start":"01:59.660 ","End":"02:01.870","Text":"the extra cellular fluid of tissues,"},{"Start":"02:01.870 ","End":"02:05.255","Text":"are maintained at an osmolarity close to that of the cytosol."},{"Start":"02:05.255 ","End":"02:09.215","Text":"It\u0027s kept somewhat at an equal osmolarity,"},{"Start":"02:09.215 ","End":"02:13.700","Text":"equal concentration of this fluid inside and outside the cell."},{"Start":"02:13.700 ","End":"02:19.490","Text":"The high concentration of albumin and other proteins in blood plasma contributes to"},{"Start":"02:19.490 ","End":"02:22.790","Text":"its osmolarity and this equal concentrations"},{"Start":"02:22.790 ","End":"02:26.705","Text":"between the cells and the interstitial fluid and plasma."},{"Start":"02:26.705 ","End":"02:31.880","Text":"Cells also pump out sodium, NA plus,"},{"Start":"02:31.880 ","End":"02:34.745","Text":"and other ions into the interstitial fluid,"},{"Start":"02:34.745 ","End":"02:37.790","Text":"to stay in osmotic balance with their surroundings."},{"Start":"02:37.790 ","End":"02:44.464","Text":"When need be, cells will pump out salts and ions so that the osmotic pressure,"},{"Start":"02:44.464 ","End":"02:48.080","Text":"the osmotic concentration outside the cell,"},{"Start":"02:48.080 ","End":"02:53.735","Text":"the interstitial fluid or plasma is closely equal to that of the cell."},{"Start":"02:53.735 ","End":"02:58.760","Text":"Therefore, it is a situation of isotonic solution,"},{"Start":"02:58.760 ","End":"03:01.820","Text":"where water enters and exits and therefore,"},{"Start":"03:01.820 ","End":"03:07.170","Text":"the cell membrane doesn\u0027t expand to the point where the cell bursts."}],"ID":28507}],"Thumbnail":null,"ID":272573},{"Name":"Ionization of Water","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Ionized water, Equilibrium Constant","Duration":"12m 57s","ChapterTopicVideoID":27664,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.295","Text":"Welcome to the topic of ionization of water,"},{"Start":"00:02.295 ","End":"00:05.580","Text":"where we specifically talk about ionized water equilibrium constant"},{"Start":"00:05.580 ","End":"00:08.640","Text":"of ionization of water and by the end of this section,"},{"Start":"00:08.640 ","End":"00:11.430","Text":"you will be able to explain the ionization of water,"},{"Start":"00:11.430 ","End":"00:13.650","Text":"describe how to measure the ionization of water,"},{"Start":"00:13.650 ","End":"00:16.770","Text":"and relate the equilibrium constant to the reactions covered."},{"Start":"00:16.770 ","End":"00:20.430","Text":"Ionization of water is when it is in the form of hydrogen ions,"},{"Start":"00:20.430 ","End":"00:24.420","Text":"H plus and hydroxide ions, OH minus."},{"Start":"00:24.420 ","End":"00:27.790","Text":"We have H plus is the hydrogen ions,"},{"Start":"00:27.790 ","End":"00:30.570","Text":"OH minus is the hydroxide ions."},{"Start":"00:30.570 ","End":"00:33.200","Text":"Let\u0027s define some terms from general chemistry"},{"Start":"00:33.200 ","End":"00:35.935","Text":"just to make sure this is clear and a reminder."},{"Start":"00:35.935 ","End":"00:39.590","Text":"Ionization. It is the process of forming or splitting"},{"Start":"00:39.590 ","End":"00:43.205","Text":"of molecules to their respective cations and anions."},{"Start":"00:43.205 ","End":"00:45.185","Text":"Usually in a molecule,"},{"Start":"00:45.185 ","End":"00:48.065","Text":"if atoms are bonded with high electronegative difference,"},{"Start":"00:48.065 ","End":"00:50.600","Text":"the bonded pair of electrons will be unequally"},{"Start":"00:50.600 ","End":"00:53.390","Text":"shared between 2 atoms which are bonded together."},{"Start":"00:53.390 ","End":"00:56.405","Text":"In that the atom which is comparatively more electronegative,"},{"Start":"00:56.405 ","End":"00:59.480","Text":"will attract the bonded pair of electrons toward itself,"},{"Start":"00:59.480 ","End":"01:04.340","Text":"so that it is slightly negatively charged and atoms which is less electronegative,"},{"Start":"01:04.340 ","End":"01:06.582","Text":"attracts less electrons towards itself."},{"Start":"01:06.582 ","End":"01:09.335","Text":"This will be the slightly positive charge."},{"Start":"01:09.335 ","End":"01:13.600","Text":"These 2 oppositely charged ions have their own terms."},{"Start":"01:13.600 ","End":"01:17.450","Text":"Cation, an atom that has a slight positive charge,"},{"Start":"01:17.450 ","End":"01:19.460","Text":"a positively charged ion."},{"Start":"01:19.460 ","End":"01:24.035","Text":"Anion, an atom that has a negatively charged ion."},{"Start":"01:24.035 ","End":"01:28.865","Text":"I had my own ways of remembering cation and anion,"},{"Start":"01:28.865 ","End":"01:31.250","Text":"which is positive, which is negative."},{"Start":"01:31.250 ","End":"01:32.810","Text":"You can go for whatever you want."},{"Start":"01:32.810 ","End":"01:35.720","Text":"I\u0027ve had people say cat ions starts with"},{"Start":"01:35.720 ","End":"01:39.150","Text":"the word cat and cats are cute and it\u0027s a positive addition,"},{"Start":"01:39.150 ","End":"01:41.150","Text":"we have cats because we want them as pets,"},{"Start":"01:41.150 ","End":"01:46.130","Text":"so that is the positive 1 and can be associated, for example,"},{"Start":"01:46.130 ","End":"01:47.960","Text":"anarchy has a negative thing,"},{"Start":"01:47.960 ","End":"01:51.950","Text":"but that\u0027s already a subjective belief."},{"Start":"01:51.950 ","End":"01:56.660","Text":"Therefore, however you remember whatever works for you, that\u0027s what you should go with."},{"Start":"01:56.660 ","End":"01:59.720","Text":"Cation is an atom that is comparatively less"},{"Start":"01:59.720 ","End":"02:04.430","Text":"electronegative and will not attract shared pair of electrons towards itself,"},{"Start":"02:04.430 ","End":"02:08.270","Text":"hence it develops that slight positive charge and to simplify this,"},{"Start":"02:08.270 ","End":"02:11.126","Text":"it is a positively charged ion, a cation."},{"Start":"02:11.126 ","End":"02:14.975","Text":"An anion which is an atom that is comparatively more electronegative,"},{"Start":"02:14.975 ","End":"02:18.170","Text":"will attract shared pair of electrons towards itself and it"},{"Start":"02:18.170 ","End":"02:21.560","Text":"develops and has a slight negative charge and in other words,"},{"Start":"02:21.560 ","End":"02:24.541","Text":"that is the negatively charged ion, the anion."},{"Start":"02:24.541 ","End":"02:29.405","Text":"While the uncharged molecule H_2O contributes to the solvent properties of water,"},{"Start":"02:29.405 ","End":"02:31.048","Text":"as we covered in a previous lesson,"},{"Start":"02:31.048 ","End":"02:33.770","Text":"the small degree of ionization of water contributes to"},{"Start":"02:33.770 ","End":"02:37.670","Text":"these properties as well as needs to be taken into account."},{"Start":"02:37.670 ","End":"02:42.635","Text":"Ionization of water is reversible and as in the case of all reversible reactions,"},{"Start":"02:42.635 ","End":"02:45.349","Text":"it can be described by an equilibrium constant."},{"Start":"02:45.349 ","End":"02:48.230","Text":"When weak acids are dissolved in water,"},{"Start":"02:48.230 ","End":"02:53.690","Text":"they contribute the hydrogen atom H plus also known as the proton."},{"Start":"02:53.690 ","End":"02:57.950","Text":"Weak bases consume H plus by becoming protonated,"},{"Start":"02:57.950 ","End":"03:02.885","Text":"transfer a proton to a molecule group of atom which forms a bond to this proton."},{"Start":"03:02.885 ","End":"03:08.240","Text":"The total hydrogen ion H plus concentration from all sources can"},{"Start":"03:08.240 ","End":"03:13.940","Text":"be measured experimentally and is expressed as the pH of the solution."},{"Start":"03:13.940 ","End":"03:16.700","Text":"To predict the state of ionization of solutes in water,"},{"Start":"03:16.700 ","End":"03:17.810","Text":"we must take into account"},{"Start":"03:17.810 ","End":"03:21.590","Text":"the relevant equilibrium constants for each ionization reaction."},{"Start":"03:21.590 ","End":"03:26.825","Text":"Let\u0027s talk about the ionization of water and weak acids and bases dissolved in water."},{"Start":"03:26.825 ","End":"03:29.450","Text":"Pure water is slightly ionized."},{"Start":"03:29.450 ","End":"03:32.840","Text":"Water molecules have a slight tendency to"},{"Start":"03:32.840 ","End":"03:36.830","Text":"undergo reversible ionization to yield a proton,"},{"Start":"03:36.830 ","End":"03:39.245","Text":"a hydrogen ion, H plus,"},{"Start":"03:39.245 ","End":"03:42.800","Text":"and a hydroxide ion OH minus,"},{"Start":"03:42.800 ","End":"03:46.740","Text":"giving the equilibrium H_2O,"},{"Start":"03:46.740 ","End":"03:51.560","Text":"resulting in H plus plus OH minus proton,"},{"Start":"03:51.560 ","End":"03:57.005","Text":"the hydrogen ion, and OH minus the hydroxide ion and this is the water molecule."},{"Start":"03:57.005 ","End":"04:01.370","Text":"This equilibrium means that it is going in a reversible fashion between"},{"Start":"04:01.370 ","End":"04:05.780","Text":"the 2 directions of this reaction when it is in the form of pure water."},{"Start":"04:05.780 ","End":"04:09.350","Text":"Although we commonly show the dissociation product water as H plus,"},{"Start":"04:09.350 ","End":"04:12.739","Text":"free protons do not exist in solution."},{"Start":"04:12.739 ","End":"04:19.370","Text":"Hydrogen formed in water are immediately hydrated to form hydronium ions H_3O plus."},{"Start":"04:19.370 ","End":"04:24.185","Text":"Since it is important that you understand this concept, I will define this again."},{"Start":"04:24.185 ","End":"04:28.565","Text":"Ionization of water, which in essence is self ionization of water or"},{"Start":"04:28.565 ","End":"04:33.815","Text":"autoionization of water is when a water molecule H_2O deprotonates,"},{"Start":"04:33.815 ","End":"04:37.400","Text":"loses a proton and forms a negatively charged ion,"},{"Start":"04:37.400 ","End":"04:39.995","Text":"an anion, OH minus hydroxide ion."},{"Start":"04:39.995 ","End":"04:42.320","Text":"When water molecule H_2O deprotonates,"},{"Start":"04:42.320 ","End":"04:45.560","Text":"loses a proton H plus and forms a negatively charged ion,"},{"Start":"04:45.560 ","End":"04:48.350","Text":"an anion OH minus the hydroxide ion,"},{"Start":"04:48.350 ","End":"04:51.320","Text":"proton formed from the water molecule instantly protonates"},{"Start":"04:51.320 ","End":"04:54.620","Text":"another water molecule and forms a hydronium ion."},{"Start":"04:54.620 ","End":"05:00.440","Text":"You have this right here what happens it instantly will find another water molecule."},{"Start":"05:00.440 ","End":"05:02.945","Text":"You will have these molecules"},{"Start":"05:02.945 ","End":"05:06.800","Text":"because it\u0027s reversible so there\u0027s constantly shift back and forth,"},{"Start":"05:06.800 ","End":"05:11.270","Text":"so you\u0027ll have all these molecules and what will happen is that these will"},{"Start":"05:11.270 ","End":"05:15.035","Text":"associate and form this hydronium ion"},{"Start":"05:15.035 ","End":"05:18.245","Text":"so that actually what you have floating around is H_2O,"},{"Start":"05:18.245 ","End":"05:21.470","Text":"OH minus, and H_3O plus."},{"Start":"05:21.470 ","End":"05:23.480","Text":"Since it\u0027s important you understand this concept,"},{"Start":"05:23.480 ","End":"05:25.745","Text":"I will define this again, ionization of water,"},{"Start":"05:25.745 ","End":"05:29.240","Text":"which in essence is self ionization of water or autoionization of"},{"Start":"05:29.240 ","End":"05:33.380","Text":"water is when a water molecule deprotonates, as you see here,"},{"Start":"05:33.380 ","End":"05:39.170","Text":"loses a proton or donates the proton and forms a negatively charged ion,"},{"Start":"05:39.170 ","End":"05:42.990","Text":"an anion OH minus, a hydroxide ion."},{"Start":"05:42.990 ","End":"05:45.725","Text":"The proton formed from the water molecule instantly protonates"},{"Start":"05:45.725 ","End":"05:51.595","Text":"another water molecule and forms hydronium ion H_3O plus."},{"Start":"05:51.595 ","End":"05:56.185","Text":"This shows the amphoteric nature of water and for,"},{"Start":"05:56.185 ","End":"06:00.515","Text":"think of amphibians that they live both on land and water so too amphoteric,"},{"Start":"06:00.515 ","End":"06:04.550","Text":"meaning it can be both an acid and a base."},{"Start":"06:04.550 ","End":"06:09.635","Text":"It can act both as an acid or a base."},{"Start":"06:09.635 ","End":"06:11.720","Text":"Again, the self ionization of water is"},{"Start":"06:11.720 ","End":"06:14.945","Text":"an ionization reaction in pure water or in an aqueous solution in which"},{"Start":"06:14.945 ","End":"06:22.780","Text":"a water molecule H_2O deprotonates to become a hydroxide ion OH minus."},{"Start":"06:22.780 ","End":"06:27.800","Text":"The hydrogen nucleus H plus the proton immediately protonates"},{"Start":"06:27.800 ","End":"06:33.210","Text":"another water molecule to form hydronium H_3O plus."},{"Start":"06:33.210 ","End":"06:37.880","Text":"What we see is 2 water molecules here,"},{"Start":"06:37.880 ","End":"06:41.150","Text":"hydrogen bonding between these 2 water molecules and it makes"},{"Start":"06:41.150 ","End":"06:44.930","Text":"the hydration of dissociating protons."},{"Start":"06:44.930 ","End":"06:48.815","Text":"This is the 3 parallel lines representing the hydrogen bond."},{"Start":"06:48.815 ","End":"06:56.285","Text":"It makes dissociation of protons virtually instantaneous so that this association,"},{"Start":"06:56.285 ","End":"07:00.335","Text":"this proton hops over you\u0027ve got H_3O plus,"},{"Start":"07:00.335 ","End":"07:04.835","Text":"and you are left with OH minus the hydroxide ion."},{"Start":"07:04.835 ","End":"07:09.500","Text":"Ionization of water can be measured by its electrical conductivity."},{"Start":"07:09.500 ","End":"07:13.370","Text":"Pure water carries electrical current as H_3O plus"},{"Start":"07:13.370 ","End":"07:17.975","Text":"migrates towards the cathode and OH minus towards the anode."},{"Start":"07:17.975 ","End":"07:21.590","Text":"Let\u0027s just step back and familiarize ourselves with the terms."},{"Start":"07:21.590 ","End":"07:24.025","Text":"Both the cathode and anode are electrodes."},{"Start":"07:24.025 ","End":"07:27.366","Text":"An electrode is a conductor that helps to establish"},{"Start":"07:27.366 ","End":"07:30.875","Text":"electrical contact with a non-metallic part of a circuit."},{"Start":"07:30.875 ","End":"07:35.570","Text":"Electrodes consist of 2 major points called cathode and anode,"},{"Start":"07:35.570 ","End":"07:40.265","Text":"as you see here, which basically describes the direction of the flow of current."},{"Start":"07:40.265 ","End":"07:43.145","Text":"A cathode can be considered an electrode from which"},{"Start":"07:43.145 ","End":"07:46.382","Text":"the current exits a polarized electrical device."},{"Start":"07:46.382 ","End":"07:49.850","Text":"Conversely, anode can be described as an electrode from which"},{"Start":"07:49.850 ","End":"07:53.885","Text":"the current enters into the polarized electrical device."},{"Start":"07:53.885 ","End":"07:57.320","Text":"The anode is the negative or reducing electrode that"},{"Start":"07:57.320 ","End":"08:01.070","Text":"releases electrons to the external circuit and oxidizes during"},{"Start":"08:01.070 ","End":"08:06.170","Text":"an electrochemical reaction while the cathode is the positive or oxidizing electrode that"},{"Start":"08:06.170 ","End":"08:08.870","Text":"acquires electrons from the external circuit"},{"Start":"08:08.870 ","End":"08:11.765","Text":"and is reduced during the electrochemical reaction."},{"Start":"08:11.765 ","End":"08:13.565","Text":"The terms cathode and anode,"},{"Start":"08:13.565 ","End":"08:17.120","Text":"and this is an FYI for the history geeks,"},{"Start":"08:17.120 ","End":"08:20.690","Text":"these terms were finalized in 1834 by William Whewell,"},{"Start":"08:20.690 ","End":"08:25.625","Text":"who adapted the words from the Greek word Kathodos."},{"Start":"08:25.625 ","End":"08:30.065","Text":"We\u0027re back to our Greek origin of words in science"},{"Start":"08:30.065 ","End":"08:35.795","Text":"and this in Greek means way down or descent."},{"Start":"08:35.795 ","End":"08:42.870","Text":"The cathode is where the current exits way down or descent, Kathodos."},{"Start":"08:42.870 ","End":"08:48.994","Text":"These terms were finalized by William after he had consulted with Michael Faraday,"},{"Start":"08:48.994 ","End":"08:52.434","Text":"that we probably know the term Faraday,"},{"Start":"08:52.434 ","End":"08:56.840","Text":"also from science and together they coined these terms."},{"Start":"08:56.840 ","End":"09:00.650","Text":"Now, the movement of hydronium and hydroxide ions in the electrical field"},{"Start":"09:00.650 ","End":"09:04.430","Text":"is extremely fast compared to that of other ions such as sodium,"},{"Start":"09:04.430 ","End":"09:06.335","Text":"potassium, chloride, NA plus,"},{"Start":"09:06.335 ","End":"09:07.835","Text":"K plus, and Cl minus."},{"Start":"09:07.835 ","End":"09:13.025","Text":"The high ionic mobility of hydronium and hydroxide"},{"Start":"09:13.025 ","End":"09:15.500","Text":"ions results from what is referred to as"},{"Start":"09:15.500 ","End":"09:19.520","Text":"proton hopping and can be seen in the figure below."},{"Start":"09:19.520 ","End":"09:23.105","Text":"What you see here is a figure depicting proton hopping."},{"Start":"09:23.105 ","End":"09:25.490","Text":"You have these water molecules,"},{"Start":"09:25.490 ","End":"09:28.520","Text":"you see the hydrogen bonding and you see the proton,"},{"Start":"09:28.520 ","End":"09:33.110","Text":"the H hopping as depicted by the red circle and this arrow over to"},{"Start":"09:33.110 ","End":"09:40.340","Text":"the next water molecule and that\u0027s in essence what we showed before in the individual."},{"Start":"09:40.340 ","End":"09:43.460","Text":"This is the proton hopping over to this water molecule."},{"Start":"09:43.460 ","End":"09:49.325","Text":"What you see here is the same idea in a chain of multiple water molecules."},{"Start":"09:49.325 ","End":"09:52.700","Text":"No individual proton was very far through the bulk solution,"},{"Start":"09:52.700 ","End":"09:54.860","Text":"but a series of proton hops between"},{"Start":"09:54.860 ","End":"09:59.015","Text":"hydrogen bonded water molecules causes the net movement of a proton over"},{"Start":"09:59.015 ","End":"10:06.560","Text":"a long distance in a remarkably short time as H_3O plus a hydronium ion,"},{"Start":"10:06.560 ","End":"10:08.330","Text":"as seen in the upper left,"},{"Start":"10:08.330 ","End":"10:14.615","Text":"gives up a proton H_2O acquires 1 becoming H_3O plus, the hydronium ion."},{"Start":"10:14.615 ","End":"10:19.228","Text":"Proton hopping is much faster than true diffusion."},{"Start":"10:19.228 ","End":"10:24.065","Text":"This explains the remarkably high ionic mobility of proton ions, H plus ions,"},{"Start":"10:24.065 ","End":"10:28.160","Text":"compared with other monovalent cations such as NA plus or K plus,"},{"Start":"10:28.160 ","End":"10:30.825","Text":"sodium plus or potassium plus."},{"Start":"10:30.825 ","End":"10:35.090","Text":"While H plus moves down this way, OH minus,"},{"Start":"10:35.090 ","End":"10:37.970","Text":"hydroxide also moves rapidly by proton hopping,"},{"Start":"10:37.970 ","End":"10:39.650","Text":"but in the opposite direction."},{"Start":"10:39.650 ","End":"10:44.315","Text":"Now, as a result of this high ionic mobility of H plus,"},{"Start":"10:44.315 ","End":"10:49.040","Text":"acid-base reactions in aqueous solutions are exceptionally fast."},{"Start":"10:49.040 ","End":"10:53.450","Text":"Because reversible ionization is crucial to the role of water in cellular function,"},{"Start":"10:53.450 ","End":"10:55.850","Text":"we must have a means of expressing the extent"},{"Start":"10:55.850 ","End":"10:58.272","Text":"of ionization of water in quantitative terms."},{"Start":"10:58.272 ","End":"11:02.600","Text":"Let\u0027s review some properties of reversible chemical reactions to show this."},{"Start":"11:02.600 ","End":"11:06.110","Text":"The position of equilibrium of any given chemical reaction"},{"Start":"11:06.110 ","End":"11:09.905","Text":"is given by its equilibrium constant K_eq for the reaction,"},{"Start":"11:09.905 ","End":"11:14.330","Text":"A plus B results in C plus D and being reversible,"},{"Start":"11:14.330 ","End":"11:15.380","Text":"you have the reactants,"},{"Start":"11:15.380 ","End":"11:18.920","Text":"you have the products and in this reversible reaction."},{"Start":"11:18.920 ","End":"11:24.170","Text":"The equilibrium constant K_eq can be defined in terms of the concentrations of"},{"Start":"11:24.170 ","End":"11:32.269","Text":"reactants A and B and products C and D at equilibrium and is given by this equation,"},{"Start":"11:32.269 ","End":"11:37.565","Text":"K_eq equals the products over the reactants and as a reminder,"},{"Start":"11:37.565 ","End":"11:40.006","Text":"the brackets denote concentration."},{"Start":"11:40.006 ","End":"11:44.600","Text":"The unit that results from this equation is molarity."},{"Start":"11:44.600 ","End":"11:47.540","Text":"The equilibrium constant is fixed and characteristic for"},{"Start":"11:47.540 ","End":"11:50.000","Text":"any given chemical reaction at a specified temperature"},{"Start":"11:50.000 ","End":"11:52.730","Text":"meaning that any chemical reaction,"},{"Start":"11:52.730 ","End":"11:57.815","Text":"there is a known equilibrium constant at a specified temperature."},{"Start":"11:57.815 ","End":"11:59.480","Text":"It defines the composition of"},{"Start":"11:59.480 ","End":"12:01.415","Text":"the final equilibrium mixture"},{"Start":"12:01.415 ","End":"12:04.730","Text":"regardless of the starting amounts of reactants and products."},{"Start":"12:04.730 ","End":"12:10.130","Text":"Conversely, we can calculate the equilibrium constant for a given reaction at"},{"Start":"12:10.130 ","End":"12:12.860","Text":"a given temperature if the equilibrium concentrations"},{"Start":"12:12.860 ","End":"12:15.990","Text":"of all its reactants and products are known."},{"Start":"12:15.990 ","End":"12:18.357","Text":"Also as we showed in previous section,"},{"Start":"12:18.357 ","End":"12:22.999","Text":"the standard free energy change Delta G is directly related"},{"Start":"12:22.999 ","End":"12:28.445","Text":"to the natural log ln of the equilibrium constant."},{"Start":"12:28.445 ","End":"12:32.690","Text":"Knowing equilibrium concentration of reactants and"},{"Start":"12:32.690 ","End":"12:37.535","Text":"products of a chemical reaction, any chemical reaction,"},{"Start":"12:37.535 ","End":"12:40.955","Text":"we can calculate the equilibrium constant and"},{"Start":"12:40.955 ","End":"12:44.870","Text":"relate it to the free energy change and with this,"},{"Start":"12:44.870 ","End":"12:48.620","Text":"we completed this section covering ionized water and the equilibrium"},{"Start":"12:48.620 ","End":"12:52.625","Text":"constant of ionization of water and we explained the ionization of water."},{"Start":"12:52.625 ","End":"12:54.575","Text":"We described how to measure the ionization of water,"},{"Start":"12:54.575 ","End":"12:58.290","Text":"and we related the equilibrium constant to the reactions covered."}],"ID":29345},{"Watched":false,"Name":"Exercise 1","Duration":"1m 22s","ChapterTopicVideoID":27665,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.710 ","End":"00:04.815","Text":"Define ionization and the 2 types of ions that form."},{"Start":"00:04.815 ","End":"00:08.160","Text":"Ionization, it is a process of forming"},{"Start":"00:08.160 ","End":"00:11.505","Text":"or splitting of molecules to their respective cations and anions."},{"Start":"00:11.505 ","End":"00:16.440","Text":"Usually, in a molecule if atoms are bonded with high electronegative difference,"},{"Start":"00:16.440 ","End":"00:18.330","Text":"the bonded pair of electrons will be unequally"},{"Start":"00:18.330 ","End":"00:20.880","Text":"shared between 2 atoms which are bonded together."},{"Start":"00:20.880 ","End":"00:25.230","Text":"That the atom, which is comparatively more electronegative,"},{"Start":"00:25.230 ","End":"00:28.560","Text":"will attract the bonded pair of electrons towards itself,"},{"Start":"00:28.560 ","End":"00:31.304","Text":"so that it is slightly negatively charged."},{"Start":"00:31.304 ","End":"00:33.930","Text":"The atom, which is less electronegative,"},{"Start":"00:33.930 ","End":"00:35.550","Text":"attracts less electrons towards itself."},{"Start":"00:35.550 ","End":"00:37.515","Text":"This will just slightly positive charge."},{"Start":"00:37.515 ","End":"00:41.445","Text":"These 2 oppositely charged ions have their own terms."},{"Start":"00:41.445 ","End":"00:46.370","Text":"Cation, an atom that is comparatively less electronegative,"},{"Start":"00:46.370 ","End":"00:49.100","Text":"will not attract shared pair of electrons towards itself,"},{"Start":"00:49.100 ","End":"00:52.570","Text":"hence develops and has a slight positive charge."},{"Start":"00:52.570 ","End":"00:55.640","Text":"Cation, an atom that is comparatively less electronegative,"},{"Start":"00:55.640 ","End":"00:58.380","Text":"will not attract shared pair of electrons towards itself,"},{"Start":"00:58.380 ","End":"01:02.060","Text":"hence it develops and has a slight positive charge."},{"Start":"01:02.060 ","End":"01:06.845","Text":"To simplify this, it is a positively charged ion, a cation."},{"Start":"01:06.845 ","End":"01:11.630","Text":"Anion, an atom that is comparatively more electronegative will attract shared pair of"},{"Start":"01:11.630 ","End":"01:17.255","Text":"electrons towards itself and it develops thus a slight negative charge."},{"Start":"01:17.255 ","End":"01:21.155","Text":"In other words, a negatively charged ion, an anion."},{"Start":"01:21.155 ","End":"01:23.790","Text":"Those are the definitions."}],"ID":29346},{"Watched":false,"Name":"Exercise 2","Duration":"4m 23s","ChapterTopicVideoID":27666,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.710 ","End":"00:04.875","Text":"Welcome to another exercise section of ionized water,"},{"Start":"00:04.875 ","End":"00:06.915","Text":"equilibrium constant of ionization of water."},{"Start":"00:06.915 ","End":"00:09.315","Text":"Part 1, which statement is true?"},{"Start":"00:09.315 ","End":"00:13.635","Text":"A, the ionized form of water is solely responsible for its solvent properties."},{"Start":"00:13.635 ","End":"00:16.890","Text":"B, weak bases become protonated when dissolved in water,"},{"Start":"00:16.890 ","End":"00:19.035","Text":"which means they lose a proton."},{"Start":"00:19.035 ","End":"00:22.020","Text":"C, ionization of water is irreversible and can be"},{"Start":"00:22.020 ","End":"00:25.155","Text":"described by an equilibrium constant or D,"},{"Start":"00:25.155 ","End":"00:28.890","Text":"the total H plus proton concentration can"},{"Start":"00:28.890 ","End":"00:33.390","Text":"be measured experimentally and is expressed as the pH of the solution."},{"Start":"00:33.390 ","End":"00:38.295","Text":"We talked about a few things here and one of them being that"},{"Start":"00:38.295 ","End":"00:43.250","Text":"the ionized form of water is part of what we find in solvents,"},{"Start":"00:43.250 ","End":"00:47.290","Text":"but it is actually also the H2O itself."},{"Start":"00:47.290 ","End":"00:53.855","Text":"If we think of this reaction and we think of the fact that this contributes,"},{"Start":"00:53.855 ","End":"00:58.820","Text":"it is not just the ionized from water that is responsible for the properties, rather,"},{"Start":"00:58.820 ","End":"01:04.145","Text":"the interaction with hydrogen bonding that happens between water molecules."},{"Start":"01:04.145 ","End":"01:09.740","Text":"Therefore, I would say A is not true and would not be a correct answer."},{"Start":"01:09.740 ","End":"01:14.720","Text":"Let\u0027s move to B, weak bases become protonated when dissolved in water sounds right,"},{"Start":"01:14.720 ","End":"01:17.030","Text":"which means they lose a proton."},{"Start":"01:17.030 ","End":"01:20.043","Text":"Well, actually protonated,"},{"Start":"01:20.043 ","End":"01:22.345","Text":"proton H plus,"},{"Start":"01:22.345 ","End":"01:24.330","Text":"means that they add,"},{"Start":"01:24.330 ","End":"01:26.520","Text":"they gain this proton."},{"Start":"01:26.520 ","End":"01:28.820","Text":"Again, they don\u0027t lose it."},{"Start":"01:28.820 ","End":"01:31.925","Text":"Therefore, this seems like it isn\u0027t true."},{"Start":"01:31.925 ","End":"01:34.910","Text":"Let\u0027s go to C, ionization of water is"},{"Start":"01:34.910 ","End":"01:38.420","Text":"irreversible and can be described by an equilibrium constant."},{"Start":"01:38.420 ","End":"01:42.800","Text":"Well, hint, I just illustrated the ionization of"},{"Start":"01:42.800 ","End":"01:48.105","Text":"water between the water molecule and H plus and OH minus."},{"Start":"01:48.105 ","End":"01:53.553","Text":"If you remember, it had those double arrows because it is reversible."},{"Start":"01:53.553 ","End":"01:58.579","Text":"There\u0027s a constant equilibrium where water is switching back and forth between"},{"Start":"01:58.579 ","End":"02:05.620","Text":"the water molecule of H2O and its ionic form."},{"Start":"02:05.620 ","End":"02:09.715","Text":"C as well, would be deemed untrue."},{"Start":"02:09.715 ","End":"02:15.368","Text":"Let\u0027s check D. The total H plus concentration can be measured experimentally,"},{"Start":"02:15.368 ","End":"02:16.415","Text":"thus far it\u0027s true,"},{"Start":"02:16.415 ","End":"02:19.175","Text":"and is expressed as the pH of the solution."},{"Start":"02:19.175 ","End":"02:24.290","Text":"Well, this sounds like it is the true statement and that we mentioned in the lesson with"},{"Start":"02:24.290 ","End":"02:30.650","Text":"regard to being able to measure the concentration experimentally."},{"Start":"02:30.650 ","End":"02:34.990","Text":"I would deem this one true. Part 2."},{"Start":"02:34.990 ","End":"02:37.625","Text":"For the statements that aren\u0027t true,"},{"Start":"02:37.625 ","End":"02:39.035","Text":"A through C,"},{"Start":"02:39.035 ","End":"02:41.135","Text":"please adjust them so that they are true."},{"Start":"02:41.135 ","End":"02:45.313","Text":"Again, we had the ionized form of water is solely responsible for its solvent properties."},{"Start":"02:45.313 ","End":"02:48.214","Text":"Hydrogen bonding, that happens between molecules"},{"Start":"02:48.214 ","End":"02:51.680","Text":"of water H2O that contributes to solvent properties,"},{"Start":"02:51.680 ","End":"02:55.070","Text":"this ability to interact and this reversible reaction."},{"Start":"02:55.070 ","End":"02:57.665","Text":"Then we can change it to say,"},{"Start":"02:57.665 ","End":"03:01.340","Text":"both the uncharged form of water and the ionized form"},{"Start":"03:01.340 ","End":"03:04.880","Text":"of water are responsible for its solvent properties."},{"Start":"03:04.880 ","End":"03:07.760","Text":"B, weak bases become protonated when dissolved in water,"},{"Start":"03:07.760 ","End":"03:09.686","Text":"which means they lose a proton."},{"Start":"03:09.686 ","End":"03:13.100","Text":"Well, protonated actually means they gain a proton."},{"Start":"03:13.100 ","End":"03:18.050","Text":"The correct sentence would be weak bases become protonated when dissolved in water,"},{"Start":"03:18.050 ","End":"03:21.200","Text":"which means that gain a proton, consume H plus."},{"Start":"03:21.200 ","End":"03:26.150","Text":"C, ionization of water is irreversible and can be described by an equilibrium constant."},{"Start":"03:26.150 ","End":"03:28.490","Text":"Well, as just illustrated during A,"},{"Start":"03:28.490 ","End":"03:32.299","Text":"it is actually a reversible reaction."},{"Start":"03:32.299 ","End":"03:34.580","Text":"Therefore, the correction would be ionization of water is"},{"Start":"03:34.580 ","End":"03:37.450","Text":"reversible and can be described by an equilibrium constant."},{"Start":"03:37.450 ","End":"03:39.995","Text":"D, we know is true from the first statement."},{"Start":"03:39.995 ","End":"03:41.405","Text":"From the first part,"},{"Start":"03:41.405 ","End":"03:43.640","Text":"the total H plus concentration can be measured"},{"Start":"03:43.640 ","End":"03:46.880","Text":"experimentally and is expressed as the pH of the solution."},{"Start":"03:46.880 ","End":"03:48.380","Text":"Totally correct and with that,"},{"Start":"03:48.380 ","End":"03:52.796","Text":"we have our 4 correct statements about water, solvent,"},{"Start":"03:52.796 ","End":"03:55.260","Text":"ionization, and A,"},{"Start":"03:55.260 ","End":"03:57.620","Text":"both uncharged form of water and the ionized form"},{"Start":"03:57.620 ","End":"04:00.080","Text":"of water are responsible for its solvent properties."},{"Start":"04:00.080 ","End":"04:03.510","Text":"Uncharged, ionized, solvent properties."},{"Start":"04:03.510 ","End":"04:06.620","Text":"B, weak bases become protonated when dissolved in water,"},{"Start":"04:06.620 ","End":"04:09.605","Text":"which means they gain a proton consume H plus."},{"Start":"04:09.605 ","End":"04:14.569","Text":"C, ionization of water is reversible and can be described by an equilibrium"},{"Start":"04:14.569 ","End":"04:17.750","Text":"constant and the total H plus concentration can be measured"},{"Start":"04:17.750 ","End":"04:22.470","Text":"experimentally and is expressed as the pH of the solution."}],"ID":29347},{"Watched":false,"Name":"Exercise 3","Duration":"1m 42s","ChapterTopicVideoID":27667,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.235","Text":"Welcome back to another exercise within the topic and section of Ionized Water,"},{"Start":"00:05.235 ","End":"00:07.920","Text":"Equilibrium Constant of Ionization of Water."},{"Start":"00:07.920 ","End":"00:11.745","Text":"Explain and describe ionization of water."},{"Start":"00:11.745 ","End":"00:14.910","Text":"Ionization of water, which in essence is self-ionization of"},{"Start":"00:14.910 ","End":"00:18.015","Text":"water or autoionization of water is when a water molecule,"},{"Start":"00:18.015 ","End":"00:22.830","Text":"H2O deprotonates, loses a proton H plus and forms a negatively charged ion,"},{"Start":"00:22.830 ","End":"00:25.770","Text":"an anion OH minus, a hydroxide ion."},{"Start":"00:25.770 ","End":"00:28.620","Text":"Proton formed from the water molecule instantly protonates"},{"Start":"00:28.620 ","End":"00:33.255","Text":"another water molecule and forms hydronium ion H3O plus."},{"Start":"00:33.255 ","End":"00:36.570","Text":"This shows that the amphoteric nature of water,"},{"Start":"00:36.570 ","End":"00:41.190","Text":"amphoteric, meaning it can act both as acid and as base."},{"Start":"00:41.190 ","End":"00:45.425","Text":"Water molecules have a slight tendency to undergo reversible ionization."},{"Start":"00:45.425 ","End":"00:48.530","Text":"This self ionization of water is an ionization reaction that occurs"},{"Start":"00:48.530 ","End":"00:51.635","Text":"in pure water or in aqueous solution and yields a proton,"},{"Start":"00:51.635 ","End":"00:53.965","Text":"a hydrogen ion, H plus,"},{"Start":"00:53.965 ","End":"00:56.650","Text":"and hydroxide ion, OH minus,"},{"Start":"00:56.650 ","End":"00:59.900","Text":"giving the equilibrium as seen here."},{"Start":"00:59.900 ","End":"01:06.065","Text":"H2O breaks apart to H plus and OH minus and these come back together to form H2O."},{"Start":"01:06.065 ","End":"01:10.635","Text":"Now, though we commonly show the dissociation product of water as H plus the proton,"},{"Start":"01:10.635 ","End":"01:12.770","Text":"free protons do not exist in solution."},{"Start":"01:12.770 ","End":"01:15.740","Text":"Rather, hydrogen molecules formed in water H plus are"},{"Start":"01:15.740 ","End":"01:19.345","Text":"immediately hydrated to form hydronium ions."},{"Start":"01:19.345 ","End":"01:21.330","Text":"H3O plus as you see here."},{"Start":"01:21.330 ","End":"01:25.295","Text":"You have the hydrogen bonding between the water molecules"},{"Start":"01:25.295 ","End":"01:29.885","Text":"makes this hydration of dissociating protons virtually instantaneous."},{"Start":"01:29.885 ","End":"01:33.650","Text":"This association, this hydrogen bonding allows for this proton from"},{"Start":"01:33.650 ","End":"01:36.020","Text":"the 1 water molecule associate with"},{"Start":"01:36.020 ","End":"01:41.370","Text":"the other water molecule and this results in the hydronium ion."}],"ID":29348},{"Watched":false,"Name":"Exercise 4","Duration":"2m 31s","ChapterTopicVideoID":27668,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.415","Text":"Welcome back to another exercise."},{"Start":"00:02.415 ","End":"00:04.215","Text":"In this section of ionized water,"},{"Start":"00:04.215 ","End":"00:06.564","Text":"equilibrium constant of ionization of water."},{"Start":"00:06.564 ","End":"00:10.185","Text":"Can and if so, how is ionization of water measured?"},{"Start":"00:10.185 ","End":"00:14.955","Text":"Yes. Ionization of water can be measured in 2 main ways."},{"Start":"00:14.955 ","End":"00:18.255","Text":"This can be done by utilizing its electrical conductivity."},{"Start":"00:18.255 ","End":"00:22.845","Text":"Pure water carries electrical current as H_3O+, hydronium ion,"},{"Start":"00:22.845 ","End":"00:26.400","Text":"migrates towards a positive electrode, the cathode,"},{"Start":"00:26.400 ","End":"00:28.230","Text":"and OH-, hydroxide ion,"},{"Start":"00:28.230 ","End":"00:30.570","Text":"towards the negative electrode, anode."},{"Start":"00:30.570 ","End":"00:33.480","Text":"Both the cathode and anode are electrodes."},{"Start":"00:33.480 ","End":"00:36.240","Text":"An electrode is a conductor that helps to establish"},{"Start":"00:36.240 ","End":"00:40.755","Text":"electrical contact with a non-metallic part of the circuit,"},{"Start":"00:40.755 ","End":"00:43.210","Text":"for example, water in-between."},{"Start":"00:43.210 ","End":"00:46.040","Text":"It can be placed in solution like"},{"Start":"00:46.040 ","End":"00:50.615","Text":"water and used to measure the solution\u0027s electrical currency."},{"Start":"00:50.615 ","End":"00:53.750","Text":"Electrodes consist of 2 major components,"},{"Start":"00:53.750 ","End":"00:55.970","Text":"the cathode and the anode."},{"Start":"00:55.970 ","End":"01:00.280","Text":"These fundamentally describe the direction of the flow of current."},{"Start":"01:00.280 ","End":"01:06.260","Text":"We mentioned they\u0027re both are types of electrodes which are conductors."},{"Start":"01:06.260 ","End":"01:09.425","Text":"A cathode is the electrode from which"},{"Start":"01:09.425 ","End":"01:13.440","Text":"the current exits in a polarized electrical device,"},{"Start":"01:13.440 ","End":"01:16.460","Text":"while the anode can be described as an electrode from"},{"Start":"01:16.460 ","End":"01:20.305","Text":"which the current enters into the polarized electrical device."},{"Start":"01:20.305 ","End":"01:24.170","Text":"In other words, combining a number of chemical terms we\u0027ve introduced previously,"},{"Start":"01:24.170 ","End":"01:27.470","Text":"the anode is the negative or reducing electrode that"},{"Start":"01:27.470 ","End":"01:31.790","Text":"releases electrons and oxidizes during an electro-chemical reaction,"},{"Start":"01:31.790 ","End":"01:35.540","Text":"while the cathode is the positive or oxidizing electrode that"},{"Start":"01:35.540 ","End":"01:39.520","Text":"acquires electrons and is reduced during the electrochemical reaction."},{"Start":"01:39.520 ","End":"01:43.430","Text":"A fact that contributes to the effectivity of this method to measure ionization of"},{"Start":"01:43.430 ","End":"01:47.560","Text":"water in solution is that the movement of hydronium, H_3O+,"},{"Start":"01:47.560 ","End":"01:49.260","Text":"and hydroxide ions, OH-,"},{"Start":"01:49.260 ","End":"01:52.550","Text":"in the electric field is extremely fast compared to that of other ions,"},{"Start":"01:52.550 ","End":"01:54.649","Text":"such as sodium, Na+, potassium,"},{"Start":"01:54.649 ","End":"01:57.365","Text":"K+, and chloride, Cl-."},{"Start":"01:57.365 ","End":"02:01.670","Text":"Furthermore, there is a means of expressing the extent of ionization of water in"},{"Start":"02:01.670 ","End":"02:08.750","Text":"quantitative terms by measuring the reaction\u0027s equilibrium constant, K_eq."},{"Start":"02:08.750 ","End":"02:12.544","Text":"As in the case of all reversible chemical reactions,"},{"Start":"02:12.544 ","End":"02:15.305","Text":"you can measure this with K equilibrium fluids,"},{"Start":"02:15.305 ","End":"02:18.110","Text":"the reversible reaction, this is the general 1,"},{"Start":"02:18.110 ","End":"02:22.575","Text":"A+B, C and D, you have reactants, and products,"},{"Start":"02:22.575 ","End":"02:23.835","Text":"and with water,"},{"Start":"02:23.835 ","End":"02:25.245","Text":"you\u0027re seeing H_2O,"},{"Start":"02:25.245 ","End":"02:29.080","Text":"to H+, and OH-."}],"ID":29349},{"Watched":false,"Name":"Equilibrium Constant of Ionization of Water","Duration":"8m 44s","ChapterTopicVideoID":27660,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.585","Text":"Hi, there. We are still within Ionization of Water."},{"Start":"00:06.585 ","End":"00:10.980","Text":"In this section, we will talk about Equilibrium Constant of Ionization of Water."},{"Start":"00:10.980 ","End":"00:12.420","Text":"By the end of this section,"},{"Start":"00:12.420 ","End":"00:14.670","Text":"you\u0027ll be able to explain the ionization of water,"},{"Start":"00:14.670 ","End":"00:16.965","Text":"describe how to measure the ionization of water,"},{"Start":"00:16.965 ","End":"00:20.500","Text":"and relate the equilibrium constant to the reactions covered."},{"Start":"00:20.500 ","End":"00:23.460","Text":"Ionization of water as defined in the previous section,"},{"Start":"00:23.460 ","End":"00:26.580","Text":"is in the form of hydrogen ions,"},{"Start":"00:26.580 ","End":"00:29.580","Text":"H plus and hydroxide ions,"},{"Start":"00:29.580 ","End":"00:32.970","Text":"OH minus, so H plus."},{"Start":"00:32.970 ","End":"00:36.965","Text":"The degree of ionization of water at equilibrium is small."},{"Start":"00:36.965 ","End":"00:43.220","Text":"The equilibrium constant for the reversible ionization of water is K_eq,"},{"Start":"00:43.220 ","End":"00:46.076","Text":"constant of equilibrium,"},{"Start":"00:46.076 ","End":"00:48.020","Text":"with the concentration of the hydrogen and"},{"Start":"00:48.020 ","End":"00:52.225","Text":"hydroxide ions over the concentration of water,"},{"Start":"00:52.225 ","End":"00:56.510","Text":"eq in a solution of water."},{"Start":"00:56.510 ","End":"01:00.290","Text":"We will refer to this as Equation 1."},{"Start":"01:00.290 ","End":"01:02.345","Text":"At 25 degrees Celsius,"},{"Start":"01:02.345 ","End":"01:09.050","Text":"2 of every 10^9 molecules in pure water are ionized at any instant."},{"Start":"01:09.050 ","End":"01:12.470","Text":"We\u0027re going to get into the actual calculation to explain this."},{"Start":"01:12.470 ","End":"01:14.420","Text":"We will number the equations in this section,"},{"Start":"01:14.420 ","End":"01:17.180","Text":"so it will be easier to follow and go back when needed."},{"Start":"01:17.180 ","End":"01:20.045","Text":"Pure water at 25 degrees Celsius,"},{"Start":"01:20.045 ","End":"01:23.075","Text":"the concentration of water is 55.5."},{"Start":"01:23.075 ","End":"01:29.410","Text":"This means the number of grams of H2O in"},{"Start":"01:29.410 ","End":"01:36.380","Text":"1 liter divided by its gram molecular weight."},{"Start":"01:36.380 ","End":"01:41.900","Text":"Molecular weight, which is a 1,000 grams per"},{"Start":"01:41.900 ","End":"01:47.600","Text":"liter over 18.015 grams per mole."},{"Start":"01:47.600 ","End":"01:49.405","Text":"This is the molecular weight."},{"Start":"01:49.405 ","End":"01:51.770","Text":"Again, in pure water at 25 degrees Celsius,"},{"Start":"01:51.770 ","End":"01:57.740","Text":"the concentration of water is 55.5 M is molarity."},{"Start":"01:57.740 ","End":"02:01.900","Text":"Molarity is grams per liter over molecular weight."},{"Start":"02:01.900 ","End":"02:05.390","Text":"Essentially, it is constant in relation to"},{"Start":"02:05.390 ","End":"02:09.245","Text":"the very low concentrations of H plus and OH minus,"},{"Start":"02:09.245 ","End":"02:15.395","Text":"which is specifically 1 times 10 to the negative 7 molarity."},{"Start":"02:15.395 ","End":"02:21.080","Text":"Accordingly, we can substitute 55.5 molars in equilibrium"},{"Start":"02:21.080 ","End":"02:28.100","Text":"constant expression to yield K equilibrium equals H plus concentration,"},{"Start":"02:28.100 ","End":"02:33.695","Text":"OH minus concentration over 55.5 molarity."},{"Start":"02:33.695 ","End":"02:37.190","Text":"Because we said that the molarity in pure water,"},{"Start":"02:37.190 ","End":"02:40.525","Text":"the concentration of water is 55.5."},{"Start":"02:40.525 ","End":"02:46.910","Text":"If here we had the original equation where it was the concentration of H2O,"},{"Start":"02:46.910 ","End":"02:52.325","Text":"then we can now replace it with this number,"},{"Start":"02:52.325 ","End":"03:00.240","Text":"which on rearranging becomes 55.5 times the equilibrium constant."},{"Start":"03:00.240 ","End":"03:02.160","Text":"We multiply it by this,"},{"Start":"03:02.160 ","End":"03:11.790","Text":"equals the concentration of hydrogen and the concentration of hydroxide ions equals K_w,"},{"Start":"03:11.790 ","End":"03:16.015","Text":"which we will refer to as Equation Number 2."},{"Start":"03:16.015 ","End":"03:21.680","Text":"K_w designates the ion product of water at 25 degrees Celsius,"},{"Start":"03:21.680 ","End":"03:27.690","Text":"with the product being 55.5 molar times K equilibrium."},{"Start":"03:27.690 ","End":"03:33.540","Text":"This right here, this product equals K_w,"},{"Start":"03:33.540 ","End":"03:39.355","Text":"so K_w equals 55.5."},{"Start":"03:39.355 ","End":"03:41.540","Text":"The value for K equilibrium,"},{"Start":"03:41.540 ","End":"03:43.310","Text":"the equilibrium constant as determined by"},{"Start":"03:43.310 ","End":"03:46.055","Text":"electrical conductivity measurements of pure water"},{"Start":"03:46.055 ","End":"03:51.515","Text":"is 1.8 times 10 to the negative 16 molarity at 25 degrees Celsius."},{"Start":"03:51.515 ","End":"03:56.775","Text":"Now, substituting this value for K equilibrium in Equation 2,"},{"Start":"03:56.775 ","End":"04:01.295","Text":"let me call this Equation 2 gives the value for the ion product of water,"},{"Start":"04:01.295 ","End":"04:08.750","Text":"K_w equals H plus OH minus equals"},{"Start":"04:08.750 ","End":"04:13.250","Text":"55.5 molarity times 1.8 times 10"},{"Start":"04:13.250 ","End":"04:17.900","Text":"to the negative 16 M because we\u0027re taking this which is K equilibrium."},{"Start":"04:17.900 ","End":"04:20.245","Text":"This is K equilibrium."},{"Start":"04:20.245 ","End":"04:28.565","Text":"We\u0027re placing that in here so we have 55.5 molarity times this right here,"},{"Start":"04:28.565 ","End":"04:34.385","Text":"equals, and we have this H plus OH minus."},{"Start":"04:34.385 ","End":"04:41.225","Text":"We can now say that K_w equals H plus"},{"Start":"04:41.225 ","End":"04:50.400","Text":"OH minus equals this right here and results in this here,"},{"Start":"04:50.400 ","End":"04:53.310","Text":"1 times 10 to the negative 14 M^2."},{"Start":"04:53.310 ","End":"04:55.410","Text":"We have this and this."},{"Start":"04:55.410 ","End":"05:01.550","Text":"Thus the product H plus OH minus an aqueous solutions at"},{"Start":"05:01.550 ","End":"05:07.565","Text":"25 degrees Celsius always equals 1 times 10 to the negative 14 M^2."},{"Start":"05:07.565 ","End":"05:09.950","Text":"Again, so if we look here,"},{"Start":"05:09.950 ","End":"05:14.705","Text":"K_w equals H plus OH minus,"},{"Start":"05:14.705 ","End":"05:16.475","Text":"the ion product,"},{"Start":"05:16.475 ","End":"05:21.950","Text":"equals 55.5M times K equilibrium would place that here,"},{"Start":"05:21.950 ","End":"05:25.590","Text":"and this is what will result in."},{"Start":"05:25.590 ","End":"05:29.630","Text":"When there are exactly equal concentrations of"},{"Start":"05:29.630 ","End":"05:35.000","Text":"hydrogen and hydroxide ions as in pure water,"},{"Start":"05:35.000 ","End":"05:38.450","Text":"the solution is said to be at neutral pH."},{"Start":"05:38.450 ","End":"05:42.110","Text":"At this pH, the concentration of H plus an OH minus can"},{"Start":"05:42.110 ","End":"05:45.804","Text":"be calculated from the ion product of water as follows."},{"Start":"05:45.804 ","End":"05:51.320","Text":"K_w equals the concentration of the proton or the hydrogen ion"},{"Start":"05:51.320 ","End":"05:57.950","Text":"times the hydroxide ion concentration equals H plus to the power of 2."},{"Start":"05:57.950 ","End":"05:59.660","Text":"Because if they are equal to each other,"},{"Start":"05:59.660 ","End":"06:02.705","Text":"we said they have equal concentrations."},{"Start":"06:02.705 ","End":"06:04.520","Text":"Then if the concentration is X,"},{"Start":"06:04.520 ","End":"06:07.730","Text":"the concentration is X as well for the hydroxide ion,"},{"Start":"06:07.730 ","End":"06:09.785","Text":"therefore, it is actually,"},{"Start":"06:09.785 ","End":"06:18.005","Text":"to be said, this squared is the concentration and the representation of K_w."},{"Start":"06:18.005 ","End":"06:22.935","Text":"Note, solving for H plus gives H plus,"},{"Start":"06:22.935 ","End":"06:30.170","Text":"we want the square root the rest of square root K_w means square root of H plus OH minus."},{"Start":"06:30.170 ","End":"06:35.765","Text":"If you remember, we said that this is always going to be"},{"Start":"06:35.765 ","End":"06:42.350","Text":"this value right here so we can now supplement that 1 times 10 to the negative 14 M^2."},{"Start":"06:42.350 ","End":"06:49.775","Text":"We square root that and that can give us hydrogen ion equals the hydroxide ion."},{"Start":"06:49.775 ","End":"06:52.730","Text":"When you square root this,"},{"Start":"06:52.730 ","End":"06:56.510","Text":"it becomes 7 because square rooting this number is to divide it"},{"Start":"06:56.510 ","End":"07:00.785","Text":"by 2 and you have the square root here and it becomes singular."},{"Start":"07:00.785 ","End":"07:05.560","Text":"Ion product of water is constant whenever"},{"Start":"07:05.560 ","End":"07:10.660","Text":"H plus is greater than 1 times 10 to the negative 7 molarity."},{"Start":"07:10.660 ","End":"07:13.760","Text":"OH minus hydroxide must become less than 1"},{"Start":"07:13.760 ","End":"07:17.405","Text":"times 10 to the negative 7 molarity and vice versa."},{"Start":"07:17.405 ","End":"07:20.405","Text":"Being that, if the constant,"},{"Start":"07:20.405 ","End":"07:22.610","Text":"the ion product water is constant,"},{"Start":"07:22.610 ","End":"07:24.770","Text":"if there\u0027s more of this,"},{"Start":"07:24.770 ","End":"07:26.570","Text":"to equal it out and keep it constant,"},{"Start":"07:26.570 ","End":"07:28.010","Text":"there needs to be less of this."},{"Start":"07:28.010 ","End":"07:31.280","Text":"If there\u0027s more of 1 times 10 to the negative 7,"},{"Start":"07:31.280 ","End":"07:34.570","Text":"there will be less of it for the hydroxide ion."},{"Start":"07:34.570 ","End":"07:38.485","Text":"When H plus is very high."},{"Start":"07:38.485 ","End":"07:41.614","Text":"As in a solution of hydrochloric acid,"},{"Start":"07:41.614 ","End":"07:46.295","Text":"HCl, OH minus must be very low."},{"Start":"07:46.295 ","End":"07:48.140","Text":"From the ion product of water,"},{"Start":"07:48.140 ","End":"07:53.450","Text":"we can calculate H plus if we know OH minus and vice versa."},{"Start":"07:53.450 ","End":"07:57.170","Text":"Now, remember of the equations we went over during this lesson,"},{"Start":"07:57.170 ","End":"07:59.960","Text":"we have equation Number 1 as we designate it,"},{"Start":"07:59.960 ","End":"08:05.075","Text":"and that is K equilibrium equals the concentration of the water ionic products,"},{"Start":"08:05.075 ","End":"08:11.345","Text":"the hydrogen ion H plus also known as the proton or the hydroxide ion, OH minus."},{"Start":"08:11.345 ","End":"08:15.350","Text":"These concentrations over the concentration of the water molecules."},{"Start":"08:15.350 ","End":"08:18.600","Text":"H2O. Equation Number 1 for K equilibrium."},{"Start":"08:18.600 ","End":"08:22.010","Text":"Equation Number 2 covers K_w for us,"},{"Start":"08:22.010 ","End":"08:26.930","Text":"taking into account 55.5 molarity times K equilibrium,"},{"Start":"08:26.930 ","End":"08:33.470","Text":"that equilibrium constant equals the hydrogen ion and the hydroxide ion of water."},{"Start":"08:33.470 ","End":"08:38.840","Text":"At this point, we completed the section and covered the ionization of water,"},{"Start":"08:38.840 ","End":"08:40.970","Text":"described how to measure the ionization of water,"},{"Start":"08:40.970 ","End":"08:45.240","Text":"and related the equilibrium constant to the reactions covered."}],"ID":29350},{"Watched":false,"Name":"Exercise 5","Duration":"1m 5s","ChapterTopicVideoID":27661,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.280","Text":"Hey, there. Welcome to exercise that\u0027s testing our knowledge"},{"Start":"00:02.280 ","End":"00:05.100","Text":"on Equilibrium Constant of Ionization of Water."},{"Start":"00:05.100 ","End":"00:09.555","Text":"What is the formula used to calculate the equilibrium constant for ionization of water?"},{"Start":"00:09.555 ","End":"00:10.710","Text":"What is another way?"},{"Start":"00:10.710 ","End":"00:12.890","Text":"Let\u0027s start with that, saying the equilibrium constant,"},{"Start":"00:12.890 ","End":"00:14.690","Text":"remember that is K_eq,"},{"Start":"00:14.690 ","End":"00:17.075","Text":"so answer K_eq,"},{"Start":"00:17.075 ","End":"00:18.880","Text":"this is the formula."},{"Start":"00:18.880 ","End":"00:21.210","Text":"Equilibrium constant for ionization of water."},{"Start":"00:21.210 ","End":"00:24.795","Text":"Water, we know the reaction generally would be."},{"Start":"00:24.795 ","End":"00:27.555","Text":"Remember, this is the reaction that we have,"},{"Start":"00:27.555 ","End":"00:29.895","Text":"H_2O going to ionization of water."},{"Start":"00:29.895 ","End":"00:33.125","Text":"To calculate the equilibrium constant for ionization of water,"},{"Start":"00:33.125 ","End":"00:37.115","Text":"we take the product over the reactant,"},{"Start":"00:37.115 ","End":"00:39.875","Text":"and that is H plus concentration and"},{"Start":"00:39.875 ","End":"00:43.170","Text":"OH minus concentration over the concentration of the water molecules,"},{"Start":"00:43.170 ","End":"00:46.850","Text":"and that would be the equilibrium constant for us."},{"Start":"00:46.850 ","End":"00:49.549","Text":"If we generally want to say K equilibrium,"},{"Start":"00:49.549 ","End":"00:51.080","Text":"we know is calculated with"},{"Start":"00:51.080 ","End":"00:53.690","Text":"the product concentration over the concentration of the reactant, and therefore,"},{"Start":"00:53.690 ","End":"00:57.301","Text":"this is why we took this from this reaction,"},{"Start":"00:57.301 ","End":"00:58.385","Text":"and in our case,"},{"Start":"00:58.385 ","End":"01:02.765","Text":"that would\u0027ve been the water molecule and a 2 ions it breaks into."},{"Start":"01:02.765 ","End":"01:06.090","Text":"The next exercise."}],"ID":29351},{"Watched":false,"Name":"Exercise 6","Duration":"2m 20s","ChapterTopicVideoID":27662,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.070","Text":"Hey there. Welcome back to an exercise testing"},{"Start":"00:02.070 ","End":"00:05.295","Text":"our knowledge on the equilibrium constant of ionization of water."},{"Start":"00:05.295 ","End":"00:07.830","Text":"What is K_w and how\u0027s it calculated?"},{"Start":"00:07.830 ","End":"00:12.405","Text":"K_w designates the ion product of water at 25 degrees Celsius."},{"Start":"00:12.405 ","End":"00:15.030","Text":"In pure water, at 25 degrees Celsius,"},{"Start":"00:15.030 ","End":"00:20.730","Text":"the concentration of water is 55.5 which means the number of grams of water, H_2O,"},{"Start":"00:20.730 ","End":"00:23.910","Text":"in 1 liter divided by its gram molecular weight,"},{"Start":"00:23.910 ","End":"00:32.325","Text":"which is 1,000 grams per liter over 18.015 grams per mole."},{"Start":"00:32.325 ","End":"00:35.999","Text":"This is the molecular weights and we are basically"},{"Start":"00:35.999 ","End":"00:41.715","Text":"dividing 55.5 moles which is number of grams of H_2O in 1 liter,"},{"Start":"00:41.715 ","End":"00:45.900","Text":"1,000 grams in 1 liter over the molecular weight."},{"Start":"00:45.900 ","End":"00:52.775","Text":"This is essentially constant in relation to the very low concentrations of H+ and OH-,"},{"Start":"00:52.775 ","End":"00:56.130","Text":"which is specifically 1 times 10 to"},{"Start":"00:56.130 ","End":"01:01.610","Text":"the negative 7 molarity which on rearranging accordingly,"},{"Start":"01:01.610 ","End":"01:05.510","Text":"we can substitute 55.5 molarity in the equilibrium constant expression to"},{"Start":"01:05.510 ","End":"01:10.700","Text":"yield K equilibrium equals the concentration of the ions,"},{"Start":"01:10.700 ","End":"01:14.510","Text":"hydrogen and hydroxide ion over 55.5 molarity,"},{"Start":"01:14.510 ","End":"01:19.470","Text":"which is what we substitute for water."},{"Start":"01:19.470 ","End":"01:21.735","Text":"Now, upon rearranging this,"},{"Start":"01:21.735 ","End":"01:29.060","Text":"your result and you multiply by 55.5 molarity and you get 55.5"},{"Start":"01:29.060 ","End":"01:36.725","Text":"times the equilibrium constant equals water ions equals the ion product."},{"Start":"01:36.725 ","End":"01:39.565","Text":"This is the ion product."},{"Start":"01:39.565 ","End":"01:43.455","Text":"We refer to this as equation Number 2."},{"Start":"01:43.455 ","End":"01:46.580","Text":"In other words, K_w is the product of the concentrations of"},{"Start":"01:46.580 ","End":"01:50.735","Text":"water times the equilibrium constant."},{"Start":"01:50.735 ","End":"01:55.070","Text":"How much of water is being ionized?"},{"Start":"01:55.070 ","End":"01:56.645","Text":"Which means that K_w,"},{"Start":"01:56.645 ","End":"02:03.780","Text":"the ion product of water at 25 degrees Celsius equals 55.5 M times"},{"Start":"02:03.780 ","End":"02:12.930","Text":"the equilibrium constant equals H+ times the concentration of OH- equals K_w."},{"Start":"02:12.940 ","End":"02:20.160","Text":"We are seeing the roundabout of this explaining it a bit further."}],"ID":29352},{"Watched":false,"Name":"Exercise 7","Duration":"2m 30s","ChapterTopicVideoID":27663,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.670","Text":"Hi there. Welcome to an exercise covering the topic"},{"Start":"00:02.670 ","End":"00:05.700","Text":"and section of equilibrium constant of ionization of water."},{"Start":"00:05.700 ","End":"00:09.300","Text":"What would the formula look like at neutral pH?"},{"Start":"00:09.300 ","End":"00:11.190","Text":"We are talking about the formula we just"},{"Start":"00:11.190 ","End":"00:15.210","Text":"covered with regarding to the equilibrium constant,"},{"Start":"00:15.210 ","End":"00:18.710","Text":"and water, and the product of ionization of water."},{"Start":"00:18.710 ","End":"00:20.370","Text":"Neutral pH means that there are"},{"Start":"00:20.370 ","End":"00:25.455","Text":"exactly equal concentrations of H plus and OH minus as in pure water."},{"Start":"00:25.455 ","End":"00:28.313","Text":"At this pH, the concentration of H plus,"},{"Start":"00:28.313 ","End":"00:32.235","Text":"and OH minus can be calculated from the ion product of water as follows."},{"Start":"00:32.235 ","End":"00:35.910","Text":"We know that the ion product of water can be expressed as such."},{"Start":"00:35.910 ","End":"00:39.335","Text":"K_w=H plus times OH minus."},{"Start":"00:39.335 ","End":"00:41.720","Text":"Basically, the ion product is"},{"Start":"00:41.720 ","End":"00:46.355","Text":"the concentration of the hydrogen ion times the concentration of the hydroxide ion."},{"Start":"00:46.355 ","End":"00:51.425","Text":"Basically, the 2 ions that are formed from water multiplied by each other."},{"Start":"00:51.425 ","End":"00:55.370","Text":"Now since H plus concentration times OH minus concentration"},{"Start":"00:55.370 ","End":"00:59.900","Text":"have equal concentrations at neutral pH,"},{"Start":"00:59.900 ","End":"01:07.280","Text":"we can actually say that the ion product is equal the same 2 products,"},{"Start":"01:07.280 ","End":"01:09.035","Text":"meaning H plus squared."},{"Start":"01:09.035 ","End":"01:16.850","Text":"Now theoretically, you can also say OH minus squared because these are equal."},{"Start":"01:16.850 ","End":"01:24.365","Text":"Now solving for H plus gives us H plus square root of the ion product."},{"Start":"01:24.365 ","End":"01:25.850","Text":"Since as we mentioned,"},{"Start":"01:25.850 ","End":"01:29.360","Text":"the product H plus times OH minus in aqueous solutions,"},{"Start":"01:29.360 ","End":"01:33.140","Text":"we have the ion product K_w at 25 degrees"},{"Start":"01:33.140 ","End":"01:38.105","Text":"Celsius always equals 1 times 10 to the negative 14th M^2."},{"Start":"01:38.105 ","End":"01:42.380","Text":"This gives us H plus equaling square root of"},{"Start":"01:42.380 ","End":"01:47.295","Text":"K_w equaling the square root of this number,"},{"Start":"01:47.295 ","End":"01:50.284","Text":"1 times 10 to the negative 14th M^2."},{"Start":"01:50.284 ","End":"01:53.150","Text":"To square a power means dividing it by 2,"},{"Start":"01:53.150 ","End":"01:57.120","Text":"which means that it is now 10 to the negative 7, and M^2,"},{"Start":"01:57.120 ","End":"01:59.640","Text":"square root of squared is single,"},{"Start":"01:59.640 ","End":"02:06.635","Text":"so you have that 8th plus equals OH minus equals 10 to the negative 7 molarity."},{"Start":"02:06.635 ","End":"02:10.580","Text":"Now an H plus hydrogen ion is very high,"},{"Start":"02:10.580 ","End":"02:13.010","Text":"as in the solution of hydrochloric acid,"},{"Start":"02:13.010 ","End":"02:16.970","Text":"HCl OH minus must be very low."},{"Start":"02:16.970 ","End":"02:18.650","Text":"From the ion product of water,"},{"Start":"02:18.650 ","End":"02:29.310","Text":"we can calculate H plus if we know OH minus concentration and vice versa."}],"ID":29353},{"Watched":false,"Name":"The pH Scale Part 1","Duration":"7m 57s","ChapterTopicVideoID":28149,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.080 ","End":"00:02.293","Text":"Hi there."},{"Start":"00:02.293 ","End":"00:04.935","Text":"We were talking about ionization of water in the chapter of Water,"},{"Start":"00:04.935 ","End":"00:08.115","Text":"and specifically introducing the pH scale."},{"Start":"00:08.115 ","End":"00:09.390","Text":"By the end of this section,"},{"Start":"00:09.390 ","End":"00:12.525","Text":"you will be able to understand the pH value,"},{"Start":"00:12.525 ","End":"00:14.205","Text":"how it is calculated,"},{"Start":"00:14.205 ","End":"00:15.975","Text":"and how it is measured."},{"Start":"00:15.975 ","End":"00:18.570","Text":"This section is going to be split to 2 parts."},{"Start":"00:18.570 ","End":"00:22.470","Text":"In Part 1, we will specifically talk about and explain the pH value,"},{"Start":"00:22.470 ","End":"00:23.730","Text":"what pH signifies,"},{"Start":"00:23.730 ","End":"00:26.250","Text":"understand pH as it relates to water,"},{"Start":"00:26.250 ","End":"00:27.780","Text":"and define the pH scale."},{"Start":"00:27.780 ","End":"00:31.755","Text":"pH tells us whether a solution is acidic or basic."},{"Start":"00:31.755 ","End":"00:33.975","Text":"According to the Arrhenius definition,"},{"Start":"00:33.975 ","End":"00:36.540","Text":"an Arrhenius acid is a substance that"},{"Start":"00:36.540 ","End":"00:40.020","Text":"dissociates in water to form hydrogen ions, H plus."},{"Start":"00:40.020 ","End":"00:42.210","Text":"Now this is named after the Swedish scientist,"},{"Start":"00:42.210 ","End":"00:43.755","Text":"Savants August Arrhenius,"},{"Start":"00:43.755 ","End":"00:45.150","Text":"originally a physicist,"},{"Start":"00:45.150 ","End":"00:46.530","Text":"but often referred to as a chemist."},{"Start":"00:46.530 ","End":"00:49.950","Text":"Arrhenius was 1 of the founders of the science of physical chemistry,"},{"Start":"00:49.950 ","End":"00:52.605","Text":"and he received the Nobel Prize for chemistry in 1903,"},{"Start":"00:52.605 ","End":"00:54.840","Text":"becoming the first Swedish Nobel laureate."},{"Start":"00:54.840 ","End":"00:58.590","Text":"An acidic solution contains H plus or H_3O plus ions,"},{"Start":"00:58.590 ","End":"01:01.970","Text":"and a basic solution contains OH minus ions."},{"Start":"01:01.970 ","End":"01:04.485","Text":"Self-dissociation of water."},{"Start":"01:04.485 ","End":"01:08.280","Text":"Even water contains a very small amount of these ions."},{"Start":"01:08.280 ","End":"01:15.165","Text":"We write the self-dissociation of water as H_2O liquid reversible reaction to the ions,"},{"Start":"01:15.165 ","End":"01:19.215","Text":"H plus aqueous plus OH minus aqueous,"},{"Start":"01:19.215 ","End":"01:24.030","Text":"or 2H_2O liquid reversible to H_3O"},{"Start":"01:24.030 ","End":"01:28.740","Text":"plus hydronium ion because we said that this never just stays on its own,"},{"Start":"01:28.740 ","End":"01:35.355","Text":"attaches to another water molecule and becomes H_3O plus aqueous and OH minus aqueous."},{"Start":"01:35.355 ","End":"01:37.665","Text":"If we see here, you have water,"},{"Start":"01:37.665 ","End":"01:42.345","Text":"and you have it breaking apart into OH minus and to H plus."},{"Start":"01:42.345 ","End":"01:46.080","Text":"Now H plus attaches to another H_2O molecule,"},{"Start":"01:46.080 ","End":"01:49.845","Text":"and becomes H_3O plus while OH minus stays here."},{"Start":"01:49.845 ","End":"01:53.065","Text":"Now talking about 2 H_2O molecules,"},{"Start":"01:53.065 ","End":"01:56.584","Text":"2 water molecules, you have 2 H_2O molecules."},{"Start":"01:56.584 ","End":"02:04.080","Text":"These will go into H_3O plus because 1 hydrogen will join the H_2O,"},{"Start":"02:04.080 ","End":"02:06.030","Text":"and you\u0027ll be left with OH minus."},{"Start":"02:06.030 ","End":"02:07.355","Text":"So you have a hydronium ion,"},{"Start":"02:07.355 ","End":"02:10.445","Text":"and a hydroxide ion starting from the water molecules."},{"Start":"02:10.445 ","End":"02:15.335","Text":"H_2O on its own water molecule breaks apart into the OH minus hydroxide ion,"},{"Start":"02:15.335 ","End":"02:16.910","Text":"and the H plus hydrogen ion."},{"Start":"02:16.910 ","End":"02:22.888","Text":"We just know that this quickly will attach this hydrogen ion to a water molecule,"},{"Start":"02:22.888 ","End":"02:24.845","Text":"and become the hydronium ion."},{"Start":"02:24.845 ","End":"02:30.590","Text":"It can experimentally be shown that H_3O hydronium"},{"Start":"02:30.590 ","End":"02:37.340","Text":"ion concentration times the hydroxide ion concentration,"},{"Start":"02:37.340 ","End":"02:47.235","Text":"which basically this equals 10^negative 14 at 25 degrees Celsius."},{"Start":"02:47.235 ","End":"02:52.095","Text":"This means the H_3O plus equals OH minus."},{"Start":"02:52.095 ","End":"02:54.680","Text":"Remember it was 10^negative 14,"},{"Start":"02:54.680 ","End":"02:59.015","Text":"but now it was for this right here."},{"Start":"02:59.015 ","End":"03:04.790","Text":"Now, you basically are trying to split it where"},{"Start":"03:04.790 ","End":"03:10.850","Text":"they\u0027re equal so each 1 is 10^negative 7th in neutral water."},{"Start":"03:10.850 ","End":"03:13.400","Text":"Step back from it, and touch up on general chemistry"},{"Start":"03:13.400 ","End":"03:15.980","Text":"and remind you what a mole is because we"},{"Start":"03:15.980 ","End":"03:21.395","Text":"were talking about the equation tells us that there are 2 moles of water,"},{"Start":"03:21.395 ","End":"03:25.860","Text":"and we\u0027ll get 1 mole of hydronium ion H_3O plus,"},{"Start":"03:25.860 ","End":"03:29.240","Text":"and 1 mole of OH minus hydroxide ion,"},{"Start":"03:29.240 ","End":"03:31.730","Text":"so that if considering what we defined,"},{"Start":"03:31.730 ","End":"03:34.235","Text":"H_3O plus as an acidic ion and"},{"Start":"03:34.235 ","End":"03:38.375","Text":"OH minus as a basic ion when we have a ratio of 1 mole to 1 mole,"},{"Start":"03:38.375 ","End":"03:41.150","Text":"then it is even, it is neutral."},{"Start":"03:41.150 ","End":"03:44.503","Text":"Therefore, we want to go back and touch up on some general chemistry,"},{"Start":"03:44.503 ","End":"03:47.120","Text":"and remind you what a mole is."},{"Start":"03:47.120 ","End":"03:50.510","Text":"A mole is the standard unit in"},{"Start":"03:50.510 ","End":"03:56.015","Text":"chemistry for measuring large quantities of very small entities."},{"Start":"03:56.015 ","End":"04:01.550","Text":"It is the base unit of amount of substance in the international system of units,"},{"Start":"04:01.550 ","End":"04:03.670","Text":"also known as SI,"},{"Start":"04:03.670 ","End":"04:11.105","Text":"and is defined as exactly 6.022 times 10^23rd particles,"},{"Start":"04:11.105 ","End":"04:13.400","Text":"also known as Avogadro\u0027s number,"},{"Start":"04:13.400 ","End":"04:15.680","Text":"which may be atoms,"},{"Start":"04:15.680 ","End":"04:18.155","Text":"molecules, ions, or electrons."},{"Start":"04:18.155 ","End":"04:20.315","Text":"Going back to the idea,"},{"Start":"04:20.315 ","End":"04:24.365","Text":"when we have a ratio of 1 mole to 1 mole then it is even, it is neutral."},{"Start":"04:24.365 ","End":"04:26.930","Text":"You have 1 mole to 1 mole,"},{"Start":"04:26.930 ","End":"04:30.685","Text":"it is neutral, 10 to the power of 7 in neutral water."},{"Start":"04:30.685 ","End":"04:32.145","Text":"If on the other hand,"},{"Start":"04:32.145 ","End":"04:36.400","Text":"H_3O plus is more than 10^negative 7,"},{"Start":"04:36.400 ","End":"04:39.395","Text":"then you can say the solution is acidic."},{"Start":"04:39.395 ","End":"04:43.640","Text":"If we have OH minus bigger than 10 to the power of 7,"},{"Start":"04:43.640 ","End":"04:47.432","Text":"which means H_3O plus is less than 10 to the power of 7,"},{"Start":"04:47.432 ","End":"04:50.044","Text":"the solution is acidic."},{"Start":"04:50.044 ","End":"04:52.940","Text":"The ion product of water,"},{"Start":"04:52.940 ","End":"04:56.030","Text":"K_w is the basis for the pH scale."},{"Start":"04:56.030 ","End":"04:59.607","Text":"The pH scale designates the H plus,"},{"Start":"04:59.607 ","End":"05:02.450","Text":"or H_3O plus and OH minus concentration."},{"Start":"05:02.450 ","End":"05:07.475","Text":"It is a convenient way to designate the concentration of hydrogen ion H plus,"},{"Start":"05:07.475 ","End":"05:09.770","Text":"or hydronium ion H_3O plus,"},{"Start":"05:09.770 ","End":"05:13.535","Text":"and thus OH minus in an aqueous solution in the range between"},{"Start":"05:13.535 ","End":"05:18.005","Text":"1 molar H plus and 1 molar OH minus."},{"Start":"05:18.005 ","End":"05:21.530","Text":"What you see here is the pH scale."},{"Start":"05:21.530 ","End":"05:25.685","Text":"The term pH is defined by the formula pH equals log of"},{"Start":"05:25.685 ","End":"05:30.710","Text":"1 over the concentration of H plus equals negative log H plus."},{"Start":"05:30.710 ","End":"05:34.775","Text":"Because if we do this negative and the H plus goes up,"},{"Start":"05:34.775 ","End":"05:36.140","Text":"and that\u0027s what we have."},{"Start":"05:36.140 ","End":"05:41.109","Text":"The symbol p denotes negative logarithm,"},{"Start":"05:41.109 ","End":"05:43.815","Text":"or log for short."},{"Start":"05:43.815 ","End":"05:48.260","Text":"For a precisely neutral solution of 25 degrees Celsius in which"},{"Start":"05:48.260 ","End":"05:52.655","Text":"the concentration of hydrogen ions is 1 times 10^negative 7 molarity,"},{"Start":"05:52.655 ","End":"05:56.995","Text":"the pH can be calculated as follows."},{"Start":"05:56.995 ","End":"06:03.670","Text":"pH equals log times 1 over 1 times 10^negative 7."},{"Start":"06:03.670 ","End":"06:05.803","Text":"Because we have the hydrogen ion down here,"},{"Start":"06:05.803 ","End":"06:07.780","Text":"and we say the hydrogen ion can be this."},{"Start":"06:07.780 ","End":"06:11.840","Text":"We take this and replace it, this factor."},{"Start":"06:11.840 ","End":"06:16.040","Text":"The pH can be calculated as seen here."},{"Start":"06:16.040 ","End":"06:22.820","Text":"The concentration of H plus must be expressed in molar terms."},{"Start":"06:22.820 ","End":"06:24.920","Text":"The value of 7 for the pH of"},{"Start":"06:24.920 ","End":"06:28.160","Text":"a precisely neutral solution is not an arbitrarily chosen figure."},{"Start":"06:28.160 ","End":"06:33.223","Text":"Rather, it is derived from the absolute value of the ion product of water,"},{"Start":"06:33.223 ","End":"06:36.650","Text":"25 degrees Celsius, which solutions with a pH that\u0027s greater"},{"Start":"06:36.650 ","End":"06:40.125","Text":"than 7 are alkaline or basic."},{"Start":"06:40.125 ","End":"06:44.645","Text":"The concentration of OH minus is greater than that of H plus."},{"Start":"06:44.645 ","End":"06:50.180","Text":"Conversely, solutions with a pH that\u0027s smaller than 7 are acidic,"},{"Start":"06:50.180 ","End":"06:56.090","Text":"and the concentration of H plus is greater than that of OH minus."},{"Start":"06:56.090 ","End":"07:02.555","Text":"Now, keep in mind that the pH scale is logarithmic, not arithmetic."},{"Start":"07:02.555 ","End":"07:04.040","Text":"A logarithm scale is"},{"Start":"07:04.040 ","End":"07:07.925","Text":"a nonlinear scale often used when analyzing a large range of quantities."},{"Start":"07:07.925 ","End":"07:10.355","Text":"Instead of increasing in equal increments,"},{"Start":"07:10.355 ","End":"07:14.525","Text":"each interval is increased by a factor of the base of the logarithm,"},{"Start":"07:14.525 ","End":"07:17.995","Text":"typically base 10 and the base scale are used,"},{"Start":"07:17.995 ","End":"07:22.410","Text":"2 solutions differ in pH by 1 unit means that 1 solution has"},{"Start":"07:22.410 ","End":"07:28.195","Text":"10 times the concentration of H plus of the other."},{"Start":"07:28.195 ","End":"07:32.825","Text":"Now this figure gives the pH values of some common aqueous fluids."},{"Start":"07:32.825 ","End":"07:35.240","Text":"A cola drink is pH 3,"},{"Start":"07:35.240 ","End":"07:39.920","Text":"a red wine is 3.7 and it has an H plus concentration"},{"Start":"07:39.920 ","End":"07:45.995","Text":"of approximately 10,000 times that of blood at pH 74."},{"Start":"07:45.995 ","End":"07:49.035","Text":"With this, we completed part 1 of the pH scale."},{"Start":"07:49.035 ","End":"07:52.190","Text":"By now you should be able to explain what the pH value is,"},{"Start":"07:52.190 ","End":"07:55.430","Text":"what pH signifies, understand pH as it relates to water,"},{"Start":"07:55.430 ","End":"07:57.960","Text":"and define the pH scale."}],"ID":29354},{"Watched":false,"Name":"The pH Scale Part 2","Duration":"6m 58s","ChapterTopicVideoID":28150,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.160","Text":"Hi, welcome back to the pH scale."},{"Start":"00:02.160 ","End":"00:05.700","Text":"This is Part 2 and Ionization of Water."},{"Start":"00:05.700 ","End":"00:07.125","Text":"By the end of this section,"},{"Start":"00:07.125 ","End":"00:12.599","Text":"you should be able to understand how pH is calculated and explain how pH is measured."},{"Start":"00:12.599 ","End":"00:15.510","Text":"The pH of an aqueous solution"},{"Start":"00:15.510 ","End":"00:19.365","Text":"can be approximately measured with the various indicator dyes,"},{"Start":"00:19.365 ","End":"00:26.940","Text":"including litmus paper, phenolphthalein, or phenol red."},{"Start":"00:26.940 ","End":"00:29.070","Text":"Now these types of indicator color changes as"},{"Start":"00:29.070 ","End":"00:32.460","Text":"a proton H^+ dissociates from the dye molecules."},{"Start":"00:32.460 ","End":"00:35.780","Text":"In other words, indicator dyes are substances that change"},{"Start":"00:35.780 ","End":"00:40.130","Text":"their color according to the acidity or basicity of the solution,"},{"Start":"00:40.130 ","End":"00:42.395","Text":"and they are often spread on filter paper."},{"Start":"00:42.395 ","End":"00:47.240","Text":"Accurate determination of pH in a chemical or clinical laboratory is made with"},{"Start":"00:47.240 ","End":"00:53.015","Text":"a glass electrode that is selectively sensitive to H^+ concentrations,"},{"Start":"00:53.015 ","End":"00:56.000","Text":"but insensitive to sodium, potassium,"},{"Start":"00:56.000 ","End":"01:00.410","Text":"and K^+, and other cations positive ions."},{"Start":"01:00.410 ","End":"01:04.460","Text":"The signal from the glass electrode is amplified and compared with the signal"},{"Start":"01:04.460 ","End":"01:09.620","Text":"generated by a solution of accurately known pH in the lab,"},{"Start":"01:09.620 ","End":"01:14.730","Text":"we currently have to calibrate and test that it is measuring accurately by dipping"},{"Start":"01:14.730 ","End":"01:20.880","Text":"the electrode in these different solutions with non-specific pH."},{"Start":"01:20.880 ","End":"01:25.320","Text":"Normally, you will dip it into 3 solutions, as you can see here,"},{"Start":"01:25.320 ","End":"01:28.100","Text":"3 colors, acidic, basic or neutral,"},{"Start":"01:28.100 ","End":"01:31.805","Text":"and see that the measure pH, as it should be."},{"Start":"01:31.805 ","End":"01:34.715","Text":"You see here, your dyes and you could see it in small,"},{"Start":"01:34.715 ","End":"01:37.760","Text":"this is 6.86, 4,"},{"Start":"01:37.760 ","End":"01:44.250","Text":"and 9.18 these are the pH that these solutions are maintained at,"},{"Start":"01:44.250 ","End":"01:48.410","Text":"and need to be checked and tested that this is actually valid."},{"Start":"01:48.410 ","End":"01:49.490","Text":"Measuring the pH is 1 of"},{"Start":"01:49.490 ","End":"01:52.190","Text":"the most important and frequently used procedures in biochemistry."},{"Start":"01:52.190 ","End":"01:55.550","Text":"The pH affects the structure and activity of biomolecules,"},{"Start":"01:55.550 ","End":"01:57.680","Text":"biological macromolecules, for example,"},{"Start":"01:57.680 ","End":"02:01.955","Text":"the catalytic activity of enzymes is strongly dependent on pH."},{"Start":"02:01.955 ","End":"02:06.395","Text":"Measurement of pH of blood and urine are commonly used in medical diagnosis."},{"Start":"02:06.395 ","End":"02:10.340","Text":"The pH of the blood plasma of people with severe uncontrolled diabetes"},{"Start":"02:10.340 ","End":"02:14.445","Text":"is often below the normal value of 7.4;"},{"Start":"02:14.445 ","End":"02:16.515","Text":"this condition is called acidosis."},{"Start":"02:16.515 ","End":"02:18.650","Text":"In specific other diseases,"},{"Start":"02:18.650 ","End":"02:22.715","Text":"the pH of the blood is higher than the normal 7.4,"},{"Start":"02:22.715 ","End":"02:25.085","Text":"a conditioned termed alkalosis."},{"Start":"02:25.085 ","End":"02:30.830","Text":"Extreme cases of either 1 acidosis or alkalosis can be life-threatening."},{"Start":"02:30.830 ","End":"02:34.925","Text":"As you see here, this is a chart of pH from 0-14,"},{"Start":"02:34.925 ","End":"02:39.380","Text":"with 0-6 being acidic,"},{"Start":"02:39.380 ","End":"02:42.870","Text":"and you have from 8 up,"},{"Start":"02:42.870 ","End":"02:44.325","Text":"which is basic,"},{"Start":"02:44.325 ","End":"02:48.005","Text":"and then you have water which is neutral."},{"Start":"02:48.005 ","End":"02:54.530","Text":"From general chemistry, hydronium ion equals the concentration of it equals 10^-7."},{"Start":"02:54.530 ","End":"03:01.935","Text":"So log_10 of the hydronium ion of H_3O^+ equals -7,"},{"Start":"03:01.935 ","End":"03:04.455","Text":"and therefore pH equals 7."},{"Start":"03:04.455 ","End":"03:07.500","Text":"If you want to do a log_10 of this,"},{"Start":"03:07.500 ","End":"03:10.315","Text":"then it becomes 10^-7,"},{"Start":"03:10.315 ","End":"03:15.820","Text":"and then we know pH is generally equal to 7."},{"Start":"03:15.820 ","End":"03:17.870","Text":"In this case, we have hydronium ion,"},{"Start":"03:17.870 ","End":"03:21.620","Text":"and there\u0027s more of it than 10^-7,"},{"Start":"03:21.620 ","End":"03:29.805","Text":"and the log_10[H_3O^+] results in a bigger value than -7,"},{"Start":"03:29.805 ","End":"03:37.570","Text":"so the pH negative log_10 of hydronium ion is smaller than 7."},{"Start":"03:37.570 ","End":"03:41.000","Text":"This is the case for an acidic solution."},{"Start":"03:41.000 ","End":"03:43.805","Text":"If we\u0027re looking at a basic solution,"},{"Start":"03:43.805 ","End":"03:46.640","Text":"H_3O^+ is smaller than 10^-7."},{"Start":"03:46.640 ","End":"03:51.830","Text":"So log_10 of [H_3O^+] is smaller than -7,"},{"Start":"03:51.830 ","End":"03:59.200","Text":"and pH equals -log_10[ H_3O^+] being bigger than 7,"},{"Start":"03:59.200 ","End":"04:02.900","Text":"and is relevant for a basic solution."},{"Start":"04:02.900 ","End":"04:05.825","Text":"Example, the pH of a solution is 6.4,"},{"Start":"04:05.825 ","End":"04:07.580","Text":"is the solution acidic or basic?"},{"Start":"04:07.580 ","End":"04:10.145","Text":"Calculate H_3O^+ and OH^-."},{"Start":"04:10.145 ","End":"04:15.095","Text":"If we look at this, this solution is acidic since the pH is smaller than 7,"},{"Start":"04:15.095 ","End":"04:20.329","Text":"everything below 7 is acidic and everything larger is basic."},{"Start":"04:20.329 ","End":"04:26.500","Text":"We previously had talked about how we can say that H_3O^+ and OH^-,"},{"Start":"04:26.500 ","End":"04:33.360","Text":"can be experimentally proven to equal 10^-14."},{"Start":"04:33.360 ","End":"04:38.840","Text":"So if we want to solve for the concentration of OH^-,"},{"Start":"04:38.840 ","End":"04:41.600","Text":"we also said that we can solve it when we have"},{"Start":"04:41.600 ","End":"04:44.975","Text":"a known value of pH and the concentration of 1 of them."},{"Start":"04:44.975 ","End":"04:50.375","Text":"We solved here for the concentration of the hydronium ion for this pH,"},{"Start":"04:50.375 ","End":"04:53.315","Text":"and what it came out to be as 10^-6.4,"},{"Start":"04:53.315 ","End":"04:57.580","Text":"or in other words, 3.98 times 10^-7."},{"Start":"04:57.580 ","End":"05:02.210","Text":"Now, if we want to solve and get the concentration of OH^-,"},{"Start":"05:02.210 ","End":"05:05.240","Text":"we divide the top portion,"},{"Start":"05:05.240 ","End":"05:08.270","Text":"which is the product of the concentrations of"},{"Start":"05:08.270 ","End":"05:12.770","Text":"both ions by the concentration of just the 1 ion,"},{"Start":"05:12.770 ","End":"05:14.500","Text":"we will get the concentration of the others."},{"Start":"05:14.500 ","End":"05:20.370","Text":"We know that the product of the concentration of hydronium and hydroxide, is 10^-14,"},{"Start":"05:20.370 ","End":"05:28.265","Text":"and we know the concentration of hydronium is 3.98 times 10^-7."},{"Start":"05:28.265 ","End":"05:32.190","Text":"Now, we can place these in the equation."},{"Start":"05:32.190 ","End":"05:35.980","Text":"You have 10^-14 over 3.98 times 10^-7."},{"Start":"05:35.980 ","End":"05:38.930","Text":"When you have such a factor,"},{"Start":"05:38.930 ","End":"05:43.250","Text":"it\u0027s like saying extra zeros to the right of the 10, 7 extra zeros."},{"Start":"05:43.250 ","End":"05:50.250","Text":"So we can eliminate the 7 extra zeros and remain with 10^-7,"},{"Start":"05:50.250 ","End":"05:52.760","Text":"and now we have this denominator,"},{"Start":"05:52.760 ","End":"05:53.840","Text":"we want this to come up."},{"Start":"05:53.840 ","End":"05:57.775","Text":"It means it is 1 decimal point moved over,"},{"Start":"05:57.775 ","End":"05:59.760","Text":"therefore, the 3.98,"},{"Start":"05:59.760 ","End":"06:01.530","Text":"we have this moving over,"},{"Start":"06:01.530 ","End":"06:03.380","Text":"and if this is algebra that you don\u0027t remember,"},{"Start":"06:03.380 ","End":"06:05.600","Text":"don\u0027t worry about it, but for those you\u0027d remember,"},{"Start":"06:05.600 ","End":"06:08.825","Text":"so now we have 0.398 times 10^-7."},{"Start":"06:08.825 ","End":"06:12.110","Text":"We generally want to keep a number with"},{"Start":"06:12.110 ","End":"06:16.670","Text":"1 at least number or digit to the left of the decimal point,"},{"Start":"06:16.670 ","End":"06:25.515","Text":"therefore, to move 1 decimal point over means we basically are multiplying this by 10."},{"Start":"06:25.515 ","End":"06:30.030","Text":"So we need to make this smaller, therefore,"},{"Start":"06:30.030 ","End":"06:33.090","Text":"we turn it into 10^-8,"},{"Start":"06:33.090 ","End":"06:35.070","Text":"and we have our answer,"},{"Start":"06:35.070 ","End":"06:38.060","Text":"and that\u0027s how we calculated the hydroxide."},{"Start":"06:38.060 ","End":"06:39.995","Text":"Again, if the algebra was confusing,"},{"Start":"06:39.995 ","End":"06:41.270","Text":"you just explain it so you understand."},{"Start":"06:41.270 ","End":"06:44.385","Text":"How we could do this so you can solve these problems,"},{"Start":"06:44.385 ","End":"06:48.380","Text":"but I\u0027m not going to review algebra more than that, and with this,"},{"Start":"06:48.380 ","End":"06:53.270","Text":"we completed the section pH scale in ionization of water in the chapter of water,"},{"Start":"06:53.270 ","End":"06:55.445","Text":"and we learned the pH value,"},{"Start":"06:55.445 ","End":"06:58.950","Text":"how it is calculated and how it is measured."}],"ID":29355},{"Watched":false,"Name":"Exercise 8","Duration":"2m 11s","ChapterTopicVideoID":27669,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.659","Text":"Hi there and welcome to the section on pH scale."},{"Start":"00:03.659 ","End":"00:07.095","Text":"We will be going through some exercises."},{"Start":"00:07.095 ","End":"00:11.925","Text":"What is the pH value and what is the basis for the pH scale?"},{"Start":"00:11.925 ","End":"00:16.725","Text":"pH tells us whether a solution is acidic or basic."},{"Start":"00:16.725 ","End":"00:18.810","Text":"According to the Arrhenius definition,"},{"Start":"00:18.810 ","End":"00:20.880","Text":"which is named after a Swedish scientist,"},{"Start":"00:20.880 ","End":"00:28.925","Text":"an Arrhenius acid is a substance that dissociates in water to form hydrogen ions, H+."},{"Start":"00:28.925 ","End":"00:30.320","Text":"The ion product of water,"},{"Start":"00:30.320 ","End":"00:33.560","Text":"K_w, is the basis for the pH scale."},{"Start":"00:33.560 ","End":"00:37.100","Text":"This is from the self dissociation of water,"},{"Start":"00:37.100 ","End":"00:42.545","Text":"H_2O liquid dissociates into its ions in aqueous solution,"},{"Start":"00:42.545 ","End":"00:48.750","Text":"H+ and OH- or 2H_2O liquids"},{"Start":"00:48.750 ","End":"00:56.160","Text":"dissociates into the ions hydronium H_3O plus aqueous plus OH-."},{"Start":"00:56.160 ","End":"00:59.720","Text":"We basically said that this is the same, but in reality,"},{"Start":"00:59.720 ","End":"01:03.305","Text":"you won\u0027t find a hydrogen ion on its own."},{"Start":"01:03.305 ","End":"01:11.660","Text":"What will happen is it will attach to an actual water molecule,"},{"Start":"01:11.660 ","End":"01:14.675","Text":"then form this right here."},{"Start":"01:14.675 ","End":"01:17.855","Text":"The pH scale designates the H plus or the hydronium,"},{"Start":"01:17.855 ","End":"01:21.590","Text":"the H3O+ and OH- concentrations."},{"Start":"01:21.590 ","End":"01:24.125","Text":"Basically, the 2 ions that form water,"},{"Start":"01:24.125 ","End":"01:26.899","Text":"hydrogen or hydronium and hydroxide."},{"Start":"01:26.899 ","End":"01:29.525","Text":"It is a convenient way to designate the concentration"},{"Start":"01:29.525 ","End":"01:32.450","Text":"of hydrogen or hydronium and thus OH,"},{"Start":"01:32.450 ","End":"01:39.575","Text":"in any aqueous solution in the range between 1 molar H+ and 1 molar OH-."},{"Start":"01:39.575 ","End":"01:43.850","Text":"The term pH is defined by the formula,"},{"Start":"01:43.850 ","End":"01:51.900","Text":"pH equals log of 1 over the concentration of hydrogen equals negative log of H+."},{"Start":"01:51.900 ","End":"01:55.670","Text":"The symbol p denotes negative logarithm of"},{"Start":"01:55.670 ","End":"02:01.470","Text":"pH basically means the negative logarithm of this."},{"Start":"02:01.470 ","End":"02:03.995","Text":"Basically, what we have here,"},{"Start":"02:03.995 ","End":"02:10.410","Text":"this means pH negative log of hydrogen ion."}],"ID":29356},{"Watched":false,"Name":"Exercise 9","Duration":"1m 56s","ChapterTopicVideoID":27670,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.550","Text":"Welcome back. We are going through exercises within the section of pH scale."},{"Start":"00:05.550 ","End":"00:09.850","Text":"To find the solution based on this information and give an example of each."},{"Start":"00:09.850 ","End":"00:13.495","Text":"A, solutions with a pH greater than 7 are?"},{"Start":"00:13.495 ","End":"00:17.145","Text":"B, solutions with a pH smaller than 7 are?"},{"Start":"00:17.145 ","End":"00:21.240","Text":"C, solutions with a pH equal to 7 are?"},{"Start":"00:21.240 ","End":"00:26.265","Text":"Well, if you can think back to the pH scale,"},{"Start":"00:26.265 ","End":"00:31.380","Text":"we had a scale where things are either smaller or bigger."},{"Start":"00:31.380 ","End":"00:37.230","Text":"They go on a spectrum from 1 all the way to 14 and the higher up,"},{"Start":"00:37.230 ","End":"00:42.300","Text":"the ones that are bigger than 7 we can say these are basic."},{"Start":"00:42.300 ","End":"00:45.780","Text":"Solutions with a pH that is greater than 7,"},{"Start":"00:45.780 ","End":"00:49.140","Text":"this means that the concentration of hydroxide ion,"},{"Start":"00:49.140 ","End":"00:54.515","Text":"OH- is greater than that of hydrogen ion, H plus."},{"Start":"00:54.515 ","End":"00:57.185","Text":"An example of this is baking soda,"},{"Start":"00:57.185 ","End":"01:00.155","Text":"bleach, sodium hydroxide, NaOH."},{"Start":"01:00.155 ","End":"01:04.355","Text":"As for B, solutions with a pH that is smaller than 7,"},{"Start":"01:04.355 ","End":"01:06.320","Text":"if you know these ones are basic or alkaline,"},{"Start":"01:06.320 ","End":"01:08.270","Text":"these ones are acidic,"},{"Start":"01:08.270 ","End":"01:11.027","Text":"and this signifies that the concentration of H+,"},{"Start":"01:11.027 ","End":"01:15.440","Text":"hydrogen ion is greater than that of hydroxide ion, OH-."},{"Start":"01:15.440 ","End":"01:18.005","Text":"Examples of these are wine,"},{"Start":"01:18.005 ","End":"01:20.720","Text":"Coca-Cola, lemon juice, coffee, and tomato juice."},{"Start":"01:20.720 ","End":"01:26.086","Text":"These are all examples of acidic solutions whereas baking soda,"},{"Start":"01:26.086 ","End":"01:31.505","Text":"bleach, these are examples of basic substances."},{"Start":"01:31.505 ","End":"01:36.590","Text":"Next, we have solutions with a pH equals 7 and these are neutral."},{"Start":"01:36.590 ","End":"01:41.825","Text":"The concentration of H+ and that OH- are equal when things are neutral."},{"Start":"01:41.825 ","End":"01:46.065","Text":"That is generally what we find in pure water,"},{"Start":"01:46.065 ","End":"01:49.220","Text":"blood, and tears are close to neutral."},{"Start":"01:49.220 ","End":"01:51.949","Text":"They\u0027re a little bit more basic than neutral,"},{"Start":"01:51.949 ","End":"01:56.250","Text":"they are 7.4 but they are quite close."}],"ID":29357},{"Watched":false,"Name":"Exercise 10","Duration":"2m 6s","ChapterTopicVideoID":27671,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.140 ","End":"00:04.530","Text":"Hey, welcome back to an exercise within the section of pH scale."},{"Start":"00:04.530 ","End":"00:09.135","Text":"The pH of an aqueous solution can be measured in 2 main approaches."},{"Start":"00:09.135 ","End":"00:13.560","Text":"pH can be approximately measured with various indicator dyes that undergo"},{"Start":"00:13.560 ","End":"00:19.245","Text":"color changes as a proton (H+) dissociates from the dye molecules."},{"Start":"00:19.245 ","End":"00:22.700","Text":"In other words, indicator dyes are substances that change their color"},{"Start":"00:22.700 ","End":"00:26.210","Text":"according to the acidity or basicity of the solution."},{"Start":"00:26.210 ","End":"00:29.240","Text":"They\u0027re often spread on filter paper."},{"Start":"00:29.240 ","End":"00:32.400","Text":"Examples, litmus paper,"},{"Start":"00:32.400 ","End":"00:35.345","Text":"phenolphthalein, and phenol red."},{"Start":"00:35.345 ","End":"00:37.130","Text":"The second approach to measurement,"},{"Start":"00:37.130 ","End":"00:39.650","Text":"an accurate determination of pH,"},{"Start":"00:39.650 ","End":"00:43.730","Text":"which is made in a chemical or clinical laboratory with"},{"Start":"00:43.730 ","End":"00:49.685","Text":"a glass electrode that is selectively sensitive to H+ to proton concentrations,"},{"Start":"00:49.685 ","End":"00:53.015","Text":"but insensitive to other cations,"},{"Start":"00:53.015 ","End":"00:56.900","Text":"such as sodium, potassium, et cetera."},{"Start":"00:56.900 ","End":"01:00.335","Text":"It measures H+ but not other positive ions."},{"Start":"01:00.335 ","End":"01:04.070","Text":"The signal and as you see here is an example of"},{"Start":"01:04.070 ","End":"01:08.000","Text":"such an electrode and the signal from which"},{"Start":"01:08.000 ","End":"01:13.025","Text":"the glass electrode is amplified and compared with the signal"},{"Start":"01:13.025 ","End":"01:19.400","Text":"generated by a solution of accurately known pH, see this here."},{"Start":"01:19.400 ","End":"01:20.780","Text":"I mentioned that in the lab,"},{"Start":"01:20.780 ","End":"01:25.250","Text":"we commonly have to calibrate and test that it is measuring accurately by dipping"},{"Start":"01:25.250 ","End":"01:31.928","Text":"the electrode in these solutions that have different known specific pH."},{"Start":"01:31.928 ","End":"01:33.080","Text":"As you see here,"},{"Start":"01:33.080 ","End":"01:36.395","Text":"you can even see the bag that\u0027s given to put in here."},{"Start":"01:36.395 ","End":"01:38.660","Text":"This is pH 9.8, this is pH 4,"},{"Start":"01:38.660 ","End":"01:40.340","Text":"this is pH 6.86,"},{"Start":"01:40.340 ","End":"01:43.718","Text":"so when you put the electrode to measure the accuracy,"},{"Start":"01:43.718 ","End":"01:45.257","Text":"and the pH, you see that it says 4,"},{"Start":"01:45.257 ","End":"01:47.810","Text":"then you would dip it in here and you\u0027d want to see that it"},{"Start":"01:47.810 ","End":"01:50.720","Text":"says 9.8 and then you know it\u0027s calibrated."},{"Start":"01:50.720 ","End":"01:53.700","Text":"You would dip it in here and it should be 6.86"},{"Start":"01:53.700 ","End":"01:57.365","Text":"and then you can use it to accurately measure pH."},{"Start":"01:57.365 ","End":"01:59.540","Text":"You would dip it into the 3 solutions,"},{"Start":"01:59.540 ","End":"02:01.130","Text":"acidic, basic and neutral,"},{"Start":"02:01.130 ","End":"02:05.970","Text":"and see that the measure pH is as it should be."}],"ID":29358},{"Watched":false,"Name":"Exercise 11","Duration":"2m 27s","ChapterTopicVideoID":27672,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.455","Text":"Hi there. We\u0027re testing our knowledge on the pH scale."},{"Start":"00:04.455 ","End":"00:07.830","Text":"Give an example of when and why measuring pH is important."},{"Start":"00:07.830 ","End":"00:09.240","Text":"Measurement of pH is one of"},{"Start":"00:09.240 ","End":"00:12.600","Text":"the most important and frequently used procedures in biochemistry,"},{"Start":"00:12.600 ","End":"00:14.595","Text":"specifically in the lab."},{"Start":"00:14.595 ","End":"00:17.310","Text":"It is known that the pH affects the structure and"},{"Start":"00:17.310 ","End":"00:20.340","Text":"activity of biomolecules, biological macromolecules,"},{"Start":"00:20.340 ","End":"00:27.215","Text":"and these are very important for viability and functionability of organisms and cells."},{"Start":"00:27.215 ","End":"00:32.675","Text":"For example, the catalytic activity of enzymes is strongly dependent on pH,"},{"Start":"00:32.675 ","End":"00:36.275","Text":"therefore measuring and knowing that it is at the appropriate pH."},{"Start":"00:36.275 ","End":"00:39.470","Text":"If you\u0027re doing an experiment in the laboratory or testing an enzyme"},{"Start":"00:39.470 ","End":"00:43.175","Text":"is important because you want to make sure that you\u0027re testing enzyme activity,"},{"Start":"00:43.175 ","End":"00:47.255","Text":"not the fact that pH is often therefore,"},{"Start":"00:47.255 ","End":"00:50.300","Text":"it\u0027s either not functioning or functioning because then you don\u0027t"},{"Start":"00:50.300 ","End":"00:53.840","Text":"have a relevant test for the enzyme."},{"Start":"00:53.840 ","End":"00:55.370","Text":"Hopefully that wasn\u0027t confusing,"},{"Start":"00:55.370 ","End":"00:56.900","Text":"but basically when you want to test something,"},{"Start":"00:56.900 ","End":"01:00.530","Text":"you want to give it all the conditions for it to function normally"},{"Start":"01:00.530 ","End":"01:05.120","Text":"and then test whatever it is that is abnormal."},{"Start":"01:05.120 ","End":"01:09.590","Text":"You want to keep the pH that you know the enzyme works in and then put"},{"Start":"01:09.590 ","End":"01:14.360","Text":"whatever inhibitor to test if the enzyme still functions, etc."},{"Start":"01:14.360 ","End":"01:18.440","Text":"Measurement of pH of blood and urine are commonly used in medical diagnosis."},{"Start":"01:18.440 ","End":"01:20.450","Text":"These can be indicative of disease."},{"Start":"01:20.450 ","End":"01:22.250","Text":"The pH of the blood plasma of people with"},{"Start":"01:22.250 ","End":"01:26.330","Text":"severe diabetes is often below the normal value of 7.4,"},{"Start":"01:26.330 ","End":"01:27.995","Text":"which is close to neutral,"},{"Start":"01:27.995 ","End":"01:31.045","Text":"and this condition is called acidosis."},{"Start":"01:31.045 ","End":"01:34.624","Text":"If it is below and remember, 1 through,"},{"Start":"01:34.624 ","End":"01:39.260","Text":"let\u0027s say 6.9 is considered acidic,"},{"Start":"01:39.260 ","End":"01:42.920","Text":"7 is neutral, and then anything you have that is"},{"Start":"01:42.920 ","End":"01:48.245","Text":"bigger than 7 is actually basic or alkaline."},{"Start":"01:48.245 ","End":"01:54.260","Text":"Now it\u0027s not actually 6.99 because it would be basically infinite before the 7."},{"Start":"01:54.260 ","End":"02:00.470","Text":"But basically the idea is that the pH of blood it is different from 7.4,"},{"Start":"02:00.470 ","End":"02:03.605","Text":"let\u0027s say it\u0027s lower then this can indicate"},{"Start":"02:03.605 ","End":"02:07.425","Text":"severe diabetes and the condition is called acidosis."},{"Start":"02:07.425 ","End":"02:08.850","Text":"In specific other diseases,"},{"Start":"02:08.850 ","End":"02:12.065","Text":"the pH of the blood is higher than the normal 7.4 conditioned termed"},{"Start":"02:12.065 ","End":"02:15.705","Text":"alkalosis, alkaline, basic."},{"Start":"02:15.705 ","End":"02:17.435","Text":"Extreme cases of either one,"},{"Start":"02:17.435 ","End":"02:20.900","Text":"acidosis or alkalosis can be life-threatening, therefore,"},{"Start":"02:20.900 ","End":"02:25.920","Text":"pH is super significant for normal functioning."}],"ID":29359},{"Watched":false,"Name":"Exercise 12","Duration":"2m 42s","ChapterTopicVideoID":27673,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.164","Text":"We\u0027re back with another question,"},{"Start":"00:03.164 ","End":"00:06.510","Text":"another practice exercise on the topic of pH scale."},{"Start":"00:06.510 ","End":"00:10.500","Text":"When a base is added to a solution, the pH should?"},{"Start":"00:10.500 ","End":"00:16.905","Text":"Base, remember, generally we have the pH scale and 1-14,"},{"Start":"00:16.905 ","End":"00:19.005","Text":"we said 7 is neutral,"},{"Start":"00:19.005 ","End":"00:26.160","Text":"so whatever is smaller than 7 or bigger than 7, that goes here,"},{"Start":"00:26.160 ","End":"00:27.630","Text":"that goes here,"},{"Start":"00:27.630 ","End":"00:30.900","Text":"said small is acidic,"},{"Start":"00:30.900 ","End":"00:33.945","Text":"bigger is basic or alkaline."},{"Start":"00:33.945 ","End":"00:36.090","Text":"When a base is added to a solution,"},{"Start":"00:36.090 ","End":"00:38.660","Text":"the pH should decrease,"},{"Start":"00:38.660 ","End":"00:40.025","Text":"increase, stay the same,"},{"Start":"00:40.025 ","End":"00:41.780","Text":"cannot tell without testing."},{"Start":"00:41.780 ","End":"00:47.455","Text":"A base has a specific pH and adding it will increase,"},{"Start":"00:47.455 ","End":"00:48.695","Text":"even if not by much,"},{"Start":"00:48.695 ","End":"00:51.545","Text":"but it will make some slight increase."},{"Start":"00:51.545 ","End":"00:53.915","Text":"Cannot tell without testing,"},{"Start":"00:53.915 ","End":"00:57.080","Text":"we wouldn\u0027t say that\u0027s true because we know the direction."},{"Start":"00:57.080 ","End":"00:58.955","Text":"We need to think, again,"},{"Start":"00:58.955 ","End":"01:01.430","Text":"remembering which direction it goes."},{"Start":"01:01.430 ","End":"01:04.490","Text":"It probably won\u0027t stay the same because if it\u0027s a base,"},{"Start":"01:04.490 ","End":"01:06.530","Text":"even if you add more and more base,"},{"Start":"01:06.530 ","End":"01:08.990","Text":"then the base becomes stronger,"},{"Start":"01:08.990 ","End":"01:11.600","Text":"the pH becomes more basic."},{"Start":"01:11.600 ","End":"01:15.030","Text":"Since the bases are bigger than 7,"},{"Start":"01:15.030 ","End":"01:20.375","Text":"the numbers on the pH scale is greater than 7 for bases,"},{"Start":"01:20.375 ","End":"01:26.245","Text":"we will say that it increases because"},{"Start":"01:26.245 ","End":"01:32.585","Text":"a decrease means it\u0027s becoming less basic or even more acidic."},{"Start":"01:32.585 ","End":"01:35.290","Text":"We know it doesn\u0027t decrease because that\u0027s"},{"Start":"01:35.290 ","End":"01:38.240","Text":"meaning it\u0027s becoming less basic or more acidic,"},{"Start":"01:38.240 ","End":"01:39.280","Text":"and if we\u0027re adding a base,"},{"Start":"01:39.280 ","End":"01:40.435","Text":"it can\u0027t be less basic."},{"Start":"01:40.435 ","End":"01:44.650","Text":"We know it won\u0027t stay the same because we\u0027re adding something that isn\u0027t neutral to"},{"Start":"01:44.650 ","End":"01:50.470","Text":"a solution and we don\u0027t need to test it in order to know that if we add a base,"},{"Start":"01:50.470 ","End":"01:54.135","Text":"alkali, we will see the pH go up."},{"Start":"01:54.135 ","End":"01:57.670","Text":"Even if we are very acidic at the level of battery acid,"},{"Start":"01:57.670 ","End":"01:59.455","Text":"if we add bleach,"},{"Start":"01:59.455 ","End":"02:04.320","Text":"it will result in some increase in the pH."},{"Start":"02:04.320 ","End":"02:08.105","Text":"What we cannot tell is if it becomes basic,"},{"Start":"02:08.105 ","End":"02:10.190","Text":"we don\u0027t know to tell that without testing,"},{"Start":"02:10.190 ","End":"02:14.610","Text":"but we can tell that pH will increase."},{"Start":"02:14.610 ","End":"02:19.955","Text":"Here you see another example of a visual of the pH scale."},{"Start":"02:19.955 ","End":"02:22.490","Text":"As we go up with the pH numbers,"},{"Start":"02:22.490 ","End":"02:24.500","Text":"it is increasingly basic,"},{"Start":"02:24.500 ","End":"02:26.990","Text":"7 is neutral, as we said,"},{"Start":"02:26.990 ","End":"02:29.003","Text":"seawater, egg whites, human blood,"},{"Start":"02:29.003 ","End":"02:30.170","Text":"tears, we talked about human blood,"},{"Start":"02:30.170 ","End":"02:32.025","Text":"tears and pure water,"},{"Start":"02:32.025 ","End":"02:33.420","Text":"they are around neutral,"},{"Start":"02:33.420 ","End":"02:36.650","Text":"human blood is a little bigger than neutral, 7.4,"},{"Start":"02:36.650 ","End":"02:41.490","Text":"a little more basic, and below it means it\u0027s increasingly acidic."}],"ID":29360},{"Watched":false,"Name":"Acids, Bases, and pKa, dissociation constants","Duration":"12m 18s","ChapterTopicVideoID":27648,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.625","Text":"Hi there. We\u0027re within the chapter of water."},{"Start":"00:02.625 ","End":"00:05.400","Text":"We are talking about the topic of ionization of"},{"Start":"00:05.400 ","End":"00:08.220","Text":"water and we are covering the section talking about acids,"},{"Start":"00:08.220 ","End":"00:11.354","Text":"bases, and pKa dissociation constants."},{"Start":"00:11.354 ","End":"00:15.060","Text":"By the end of this section, we\u0027ll be able to describe ionization of acids and bases,"},{"Start":"00:15.060 ","End":"00:19.275","Text":"the behavior of aqueous solutions of weak acids and bases, and titration curves."},{"Start":"00:19.275 ","End":"00:22.260","Text":"Acids may be defined as proton donors,"},{"Start":"00:22.260 ","End":"00:25.050","Text":"while bases as proton acceptors."},{"Start":"00:25.050 ","End":"00:30.540","Text":"A proton donor and its corresponding proton acceptor make up a conjugate acid-base pair."},{"Start":"00:30.540 ","End":"00:35.280","Text":"For example, we have acetic acid, CH_3, COOH,"},{"Start":"00:35.280 ","End":"00:39.824","Text":"a proton donor and we have the acetate and acetate"},{"Start":"00:39.824 ","End":"00:44.690","Text":"anion CH_3COO minus the corresponding proton acceptor."},{"Start":"00:44.690 ","End":"00:47.795","Text":"You have this that donates this proton,"},{"Start":"00:47.795 ","End":"00:51.310","Text":"and you have this that accepts a proton,"},{"Start":"00:51.310 ","End":"00:57.005","Text":"and these together constitute a conjugate acid-base pair which can be related by"},{"Start":"00:57.005 ","End":"01:03.085","Text":"the reversible reaction CH_3COOH dissociate into H plus,"},{"Start":"01:03.085 ","End":"01:08.525","Text":"plus CH_3COO minus you have the proton that was donated."},{"Start":"01:08.525 ","End":"01:13.745","Text":"Each acid has a characteristic tendency to lose its proton in aqueous solution."},{"Start":"01:13.745 ","End":"01:15.280","Text":"The stronger the acid,"},{"Start":"01:15.280 ","End":"01:17.855","Text":"the greater tendency to lose its proton,"},{"Start":"01:17.855 ","End":"01:19.970","Text":"the greater this will happen,"},{"Start":"01:19.970 ","End":"01:22.205","Text":"meaning the arrow may be stronger,"},{"Start":"01:22.205 ","End":"01:29.090","Text":"going to the right where you\u0027re losing your proton whatever this acid is."},{"Start":"01:29.090 ","End":"01:34.895","Text":"Now the tendency of any acid HA to lose a proton and form its conjugate base"},{"Start":"01:34.895 ","End":"01:37.835","Text":"a minus is defined by the equilibrium constant"},{"Start":"01:37.835 ","End":"01:41.390","Text":"K equilibrium for the reversible reaction HA."},{"Start":"01:41.390 ","End":"01:43.460","Text":"Again, this is an acid,"},{"Start":"01:43.460 ","End":"01:46.375","Text":"this is just represent an acid."},{"Start":"01:46.375 ","End":"01:51.590","Text":"You have the products H plus plus 8 minus."},{"Start":"01:51.590 ","End":"01:53.600","Text":"This is the conjugate base."},{"Start":"01:53.600 ","End":"01:57.515","Text":"Now taking that this is the reversible reaction."},{"Start":"01:57.515 ","End":"02:01.625","Text":"The formula to calculate it as K equilibrium equals"},{"Start":"02:01.625 ","End":"02:07.550","Text":"the products H plus and A minus the conjugate base over the reactant,"},{"Start":"02:07.550 ","End":"02:10.105","Text":"which is HA, the acid."},{"Start":"02:10.105 ","End":"02:12.375","Text":"That equals K_a,"},{"Start":"02:12.375 ","End":"02:18.740","Text":"the ionization constant or also known as the dissociation constants."},{"Start":"02:18.740 ","End":"02:22.640","Text":"Equilibrium constants for ionization reactions are usually"},{"Start":"02:22.640 ","End":"02:27.310","Text":"called ionization or dissociation constants,"},{"Start":"02:27.310 ","End":"02:29.250","Text":"K subscript a, you\u0027ll see"},{"Start":"02:29.250 ","End":"02:34.130","Text":"different variability with the dissociation or ionization constant."},{"Start":"02:34.130 ","End":"02:38.630","Text":"If you have a stronger acids such as phosphoric acid and carbonic acid,"},{"Start":"02:38.630 ","End":"02:41.225","Text":"they will have a larger dissociation constant,"},{"Start":"02:41.225 ","End":"02:44.705","Text":"more of a tendency to give up and donate a proton."},{"Start":"02:44.705 ","End":"02:48.242","Text":"While weaker acids such as monohydrogen phosphate,"},{"Start":"02:48.242 ","End":"02:52.249","Text":"HPO_4_2 minus have smaller dissociation constants"},{"Start":"02:52.249 ","End":"02:55.790","Text":"because they will generally not dissociate from their proton."},{"Start":"02:55.790 ","End":"02:58.940","Text":"Reiterating this, stronger acids such as phosphoric acid"},{"Start":"02:58.940 ","End":"03:02.269","Text":"and carbonic acids have larger dissociation constant."},{"Start":"03:02.269 ","End":"03:05.885","Text":"While weaker acids such as monohydrogen phosphate,"},{"Start":"03:05.885 ","End":"03:09.455","Text":"HPO_4_2 has a smaller dissociation constant."},{"Start":"03:09.455 ","End":"03:13.160","Text":"If we\u0027re looking at an acid or a base,"},{"Start":"03:13.160 ","End":"03:19.550","Text":"a strong acid will have a high tendency to give away the hydrogen, the proton."},{"Start":"03:19.550 ","End":"03:26.225","Text":"A strong base will have the tendency to accept the proton,"},{"Start":"03:26.225 ","End":"03:30.554","Text":"this acid, this HCl because it donated the proton."},{"Start":"03:30.554 ","End":"03:34.235","Text":"Remember, H plus in an aqueous solution,"},{"Start":"03:34.235 ","End":"03:39.740","Text":"water will attach the water molecule and become a H_3O plus and then you have"},{"Start":"03:39.740 ","End":"03:45.285","Text":"complete dissociation of the acid where Cl minuses on its own."},{"Start":"03:45.285 ","End":"03:54.340","Text":"Again, just not to confuse HCl with complete dissociation becomes H plus plus Cl minus."},{"Start":"03:54.340 ","End":"03:57.320","Text":"Again, the reason we\u0027re seeing H_3O plus because"},{"Start":"03:57.320 ","End":"04:00.530","Text":"it\u0027s H plus right away associates with water."},{"Start":"04:00.530 ","End":"04:02.884","Text":"Now if you look here at this weak acid,"},{"Start":"04:02.884 ","End":"04:06.470","Text":"what happens is that there will be some dissociation,"},{"Start":"04:06.470 ","End":"04:10.610","Text":"some of the proton or the hydrogen ions will attach the water to"},{"Start":"04:10.610 ","End":"04:15.070","Text":"get the HO plus and part of the acid,"},{"Start":"04:15.070 ","End":"04:16.250","Text":"but it won\u0027t be complete."},{"Start":"04:16.250 ","End":"04:17.809","Text":"There will be a back-and-forth,"},{"Start":"04:17.809 ","End":"04:20.180","Text":"whereas you see the arrow is a strong area to the right here,"},{"Start":"04:20.180 ","End":"04:21.590","Text":"you\u0027ll see they\u0027ll go back and forth."},{"Start":"04:21.590 ","End":"04:24.230","Text":"They will interchange. They will re-associate,"},{"Start":"04:24.230 ","End":"04:26.260","Text":"dissociate, re-associate, dissociate."},{"Start":"04:26.260 ","End":"04:28.820","Text":"With the bases, the idea that is similar,"},{"Start":"04:28.820 ","End":"04:31.310","Text":"pKa, which is analogous to pH,"},{"Start":"04:31.310 ","End":"04:40.375","Text":"is defined by the equation K_a equals log 1 over K_a and that equals negative log of K_a."},{"Start":"04:40.375 ","End":"04:44.267","Text":"The stronger the tendency to dissociate a proton,"},{"Start":"04:44.267 ","End":"04:45.470","Text":"as in the strong acid,"},{"Start":"04:45.470 ","End":"04:48.415","Text":"the stronger the acid and the lower its pKa."},{"Start":"04:48.415 ","End":"04:51.920","Text":"The strong acids are completely ionized and dilute aqueous solution,"},{"Start":"04:51.920 ","End":"04:54.650","Text":"and strong bases also completely ionized."},{"Start":"04:54.650 ","End":"04:57.710","Text":"For seeing it, the strong base in water,"},{"Start":"04:57.710 ","End":"05:00.015","Text":"you have NaOH."},{"Start":"05:00.015 ","End":"05:01.774","Text":"It completely de-ionizes."},{"Start":"05:01.774 ","End":"05:04.385","Text":"You have Na, sodium ion,"},{"Start":"05:04.385 ","End":"05:08.600","Text":"and OH minus hydroxide ion, completely dissociated."},{"Start":"05:08.600 ","End":"05:11.780","Text":"Weak acids and bases do not completely ionize when"},{"Start":"05:11.780 ","End":"05:15.230","Text":"dissolved in water and this is common in biological systems."},{"Start":"05:15.230 ","End":"05:19.070","Text":"You see that back and forth between the 2 states."},{"Start":"05:19.070 ","End":"05:20.825","Text":"Now let\u0027s talk about titration curves."},{"Start":"05:20.825 ","End":"05:25.009","Text":"These reveal the pKa of weak acids."},{"Start":"05:25.009 ","End":"05:27.890","Text":"Titration is used to determine the amount of"},{"Start":"05:27.890 ","End":"05:31.220","Text":"an acid in a given solution. How is this done?"},{"Start":"05:31.220 ","End":"05:35.930","Text":"A measured volume of the acid is titrated with a solution of strong base."},{"Start":"05:35.930 ","End":"05:38.779","Text":"Usually, it is sodium hydroxide,"},{"Start":"05:38.779 ","End":"05:41.420","Text":"NaOH of known concentration."},{"Start":"05:41.420 ","End":"05:47.630","Text":"Anyways, sodium hydroxide is added in small increments until the acid is consumed,"},{"Start":"05:47.630 ","End":"05:54.065","Text":"meaning neutralized, as determined with the indicator dye or a pH meter."},{"Start":"05:54.065 ","End":"05:57.565","Text":"Remember, we talked about how to measure pH."},{"Start":"05:57.565 ","End":"06:01.010","Text":"The concentration of the acid and the original solution can be calculated from"},{"Start":"06:01.010 ","End":"06:04.415","Text":"the volume and concentration of NaOH added, meaning titrated."},{"Start":"06:04.415 ","End":"06:09.005","Text":"This is the titration curve and it reveals the pKa of the weak acid."},{"Start":"06:09.005 ","End":"06:12.650","Text":"Consider the titration of 0.1 molar solution of acetic acid with"},{"Start":"06:12.650 ","End":"06:16.385","Text":"0.1 molar sodium hydroxide at 25 degrees Celsius."},{"Start":"06:16.385 ","End":"06:18.200","Text":"This is our base right here."},{"Start":"06:18.200 ","End":"06:20.829","Text":"This is what we\u0027re using to titrate."},{"Start":"06:20.829 ","End":"06:23.420","Text":"2 reversible equilibria are involved in the process."},{"Start":"06:23.420 ","End":"06:28.985","Text":"You have H_2O that dissociates to its ions H plus and OH minus and then you have HAc,"},{"Start":"06:28.985 ","End":"06:34.530","Text":"acetic acid that also dissociates to H plus and Ac minus."},{"Start":"06:34.530 ","End":"06:39.320","Text":"The equilibrium simultaneously conformed to their characteristic equilibrium constants,"},{"Start":"06:39.320 ","End":"06:45.035","Text":"which are respectively K_w equals the concentration of the 2 other products."},{"Start":"06:45.035 ","End":"06:49.935","Text":"Their product equals 1 times 10 to the negative 14 m squared."},{"Start":"06:49.935 ","End":"06:51.445","Text":"As for K_a,"},{"Start":"06:51.445 ","End":"06:56.750","Text":"we have the concentration of N and this is for the acid\u0027s proton H plus or"},{"Start":"06:56.750 ","End":"07:02.270","Text":"hydrogen ion and the Ac minus over the molecule of them,"},{"Start":"07:02.270 ","End":"07:08.445","Text":"both the actual acid HAc and this equals 1 times 74 times 10^5 molar."},{"Start":"07:08.445 ","End":"07:10.400","Text":"At the beginning of the titration,"},{"Start":"07:10.400 ","End":"07:12.350","Text":"before any sodium hydroxide is added,"},{"Start":"07:12.350 ","End":"07:15.020","Text":"the acetic acid is slightly ionized,"},{"Start":"07:15.020 ","End":"07:19.805","Text":"to an extent that can be calculated from its dissociation constant."},{"Start":"07:19.805 ","End":"07:21.800","Text":"As sodium hydroxide is introduced,"},{"Start":"07:21.800 ","End":"07:23.030","Text":"as NaOH is introduced,"},{"Start":"07:23.030 ","End":"07:26.690","Text":"the added OH from the sodium hydroxide"},{"Start":"07:26.690 ","End":"07:31.220","Text":"combines with the free H plus in the solution to form H_2O."},{"Start":"07:31.220 ","End":"07:36.020","Text":"At the midpoint, half of the original acetic acid has undergone dissociation,"},{"Start":"07:36.020 ","End":"07:37.920","Text":"it has done this,"},{"Start":"07:37.920 ","End":"07:41.675","Text":"now equals that of the proton acceptor."},{"Start":"07:41.675 ","End":"07:43.759","Text":"As free hydrogen is removed,"},{"Start":"07:43.759 ","End":"07:47.795","Text":"HAc dissociates further to satisfy its own equilibrium constant,"},{"Start":"07:47.795 ","End":"07:49.610","Text":"then that results at the titration,"},{"Start":"07:49.610 ","End":"07:52.685","Text":"is that more and more HAc ionizes,"},{"Start":"07:52.685 ","End":"07:57.085","Text":"forming Ac as the sodium hydroxide is added."},{"Start":"07:57.085 ","End":"07:59.930","Text":"We talked about the pH of acetic acid and acetate."},{"Start":"07:59.930 ","End":"08:03.470","Text":"It is equal to the pKa of acetic acid,"},{"Start":"08:03.470 ","End":"08:04.715","Text":"as you can see here."},{"Start":"08:04.715 ","End":"08:06.710","Text":"As the titration continues,"},{"Start":"08:06.710 ","End":"08:10.100","Text":"the remaining acetic acid is converted into acetate."},{"Start":"08:10.100 ","End":"08:11.285","Text":"If you see here,"},{"Start":"08:11.285 ","End":"08:13.085","Text":"we\u0027re starting with CH_3COOH,"},{"Start":"08:13.085 ","End":"08:15.140","Text":"this is where it starts."},{"Start":"08:15.140 ","End":"08:17.405","Text":"NaOH is being titrated,"},{"Start":"08:17.405 ","End":"08:19.580","Text":"as you could see here over time,"},{"Start":"08:19.580 ","End":"08:22.235","Text":"and over time you see this S-curve."},{"Start":"08:22.235 ","End":"08:27.710","Text":"What\u0027s happening is the pH is rising because base solution is being added."},{"Start":"08:27.710 ","End":"08:29.600","Text":"This is where the pH,"},{"Start":"08:29.600 ","End":"08:32.075","Text":"the pKa, 4.76."},{"Start":"08:32.075 ","End":"08:36.440","Text":"We\u0027re actually adding a little bit of acid that aren\u0027t very strong."},{"Start":"08:36.440 ","End":"08:40.790","Text":"We\u0027ll still leave it in this buffering region where it will stay."},{"Start":"08:40.790 ","End":"08:44.990","Text":"If you add enough of the sodium hydroxide or whatever base you are adding,"},{"Start":"08:44.990 ","End":"08:50.750","Text":"then it will break out of this buffering region and become a basic solution."},{"Start":"08:50.750 ","End":"08:55.375","Text":"To the endpoint of the titration occurs at p 87,"},{"Start":"08:55.375 ","End":"08:59.270","Text":"so looking here at the midpoint of the titration at which"},{"Start":"08:59.270 ","End":"09:03.320","Text":"exactly 0.5 equivalent of sodium hydroxide has been added,"},{"Start":"09:03.320 ","End":"09:06.875","Text":"1.5 of the original acetic acid has undergone dissociation."},{"Start":"09:06.875 ","End":"09:12.395","Text":"Therefore, the concentration of the proton donor, the CH_3COOH,"},{"Start":"09:12.395 ","End":"09:17.045","Text":"which is also referred to as HAc,"},{"Start":"09:17.045 ","End":"09:21.050","Text":"now equals that of the proton acceptor."},{"Start":"09:21.050 ","End":"09:25.505","Text":"As you see here, that can be generally termed Ac minus."},{"Start":"09:25.505 ","End":"09:29.030","Text":"In our case, it\u0027s CH_3COO minus."},{"Start":"09:29.030 ","End":"09:32.465","Text":"At this midpoint, a very important relationship holds,"},{"Start":"09:32.465 ","End":"09:36.380","Text":"pH of the equal molar solution of acetic acid and acetate"},{"Start":"09:36.380 ","End":"09:40.385","Text":"is exactly equal to the pKa of acetic acid,"},{"Start":"09:40.385 ","End":"09:48.830","Text":"pKa for 76, meaning the pH and the pKa here are equal and they are 4.76."},{"Start":"09:48.830 ","End":"09:51.200","Text":"Again, the pH of the equal molar solution of"},{"Start":"09:51.200 ","End":"09:54.799","Text":"acetic acid and acetate when they\u0027re equal N moles,"},{"Start":"09:54.799 ","End":"10:01.245","Text":"the pH equals the pKA of acidic acid, that is 4.76."},{"Start":"10:01.245 ","End":"10:06.935","Text":"All the acetic acid has lost its protons to OH minus to form H_2O and acetate."},{"Start":"10:06.935 ","End":"10:09.830","Text":"Through the titration, the 2 equilibria co-exist,"},{"Start":"10:09.830 ","End":"10:12.620","Text":"each conforming to its equilibrium constant."},{"Start":"10:12.620 ","End":"10:15.440","Text":"Now, here what you see is a comparison of"},{"Start":"10:15.440 ","End":"10:19.670","Text":"the titration curves of 3 weak acids with very different association curves,"},{"Start":"10:19.670 ","End":"10:22.495","Text":"acetic acid with pKa,"},{"Start":"10:22.495 ","End":"10:26.445","Text":"4.76, it\u0027s an acid to lower than 7."},{"Start":"10:26.445 ","End":"10:29.220","Text":"The hydrogen phosphate H_2PO_4,"},{"Start":"10:29.220 ","End":"10:31.370","Text":"by the H_2,"},{"Start":"10:31.370 ","End":"10:35.300","Text":"you could guess a little more acidic than neutral."},{"Start":"10:35.300 ","End":"10:37.940","Text":"The pKa for that is 6.86,"},{"Start":"10:37.940 ","End":"10:39.695","Text":"it\u0027s still lower than 7,"},{"Start":"10:39.695 ","End":"10:41.075","Text":"than the neutral pH,"},{"Start":"10:41.075 ","End":"10:43.340","Text":"it is therefore considered acidic."},{"Start":"10:43.340 ","End":"10:45.780","Text":"Then we have the ammonium ion,"},{"Start":"10:45.780 ","End":"10:47.600","Text":"this is our third example."},{"Start":"10:47.600 ","End":"10:50.194","Text":"Now as you could see, the S-curves are very similar."},{"Start":"10:50.194 ","End":"10:57.465","Text":"The ammonium ion NH_4 plus has the pKa of 9.25."},{"Start":"10:57.465 ","End":"11:00.505","Text":"This is the midpoint of titration."},{"Start":"11:00.505 ","End":"11:04.052","Text":"Again, this figure compares the titration curves,"},{"Start":"11:04.052 ","End":"11:08.840","Text":"the 3 weak acids with very different dissociation constants with acetic acid,"},{"Start":"11:08.840 ","End":"11:13.545","Text":"the hydrogen phosphate, and ammonium ion."},{"Start":"11:13.545 ","End":"11:16.100","Text":"These are the 3 that we are looking at here."},{"Start":"11:16.100 ","End":"11:17.540","Text":"We have this one,"},{"Start":"11:17.540 ","End":"11:20.015","Text":"this one, and this one."},{"Start":"11:20.015 ","End":"11:23.830","Text":"Now although the titration curves are these acids have the same shape,"},{"Start":"11:23.830 ","End":"11:29.090","Text":"they are displaced along the pH axis because the 3 acids have different strengths."},{"Start":"11:29.090 ","End":"11:31.730","Text":"Acetic acid with the highest K,"},{"Start":"11:31.730 ","End":"11:35.270","Text":"lowest pK of the 3 is the strongest,"},{"Start":"11:35.270 ","End":"11:37.775","Text":"loses its proton most readily."},{"Start":"11:37.775 ","End":"11:41.840","Text":"It is already have dissociated pH 4.76."},{"Start":"11:41.840 ","End":"11:48.779","Text":"The hydrogen phosphate loses a proton less readily being half associated at pH 6.86."},{"Start":"11:48.779 ","End":"11:52.010","Text":"Ammonium ion is the weakest acid with 3"},{"Start":"11:52.010 ","End":"11:57.395","Text":"and it does not become half to associate it until pH 9.25."},{"Start":"11:57.395 ","End":"11:59.990","Text":"The most important point about the titration curve of"},{"Start":"11:59.990 ","End":"12:02.750","Text":"weak acid is that it shows graphically that"},{"Start":"12:02.750 ","End":"12:09.065","Text":"a weak acid and its anion conjugate acid-base pair can act as a buffer."},{"Start":"12:09.065 ","End":"12:12.980","Text":"We should now be able to explain ionization of acids and bases toward"},{"Start":"12:12.980 ","End":"12:15.170","Text":"the behavior of aqueous solutions of weak acids and"},{"Start":"12:15.170 ","End":"12:18.780","Text":"bases and talk about titration curves."}],"ID":29361},{"Watched":false,"Name":"Exercise 13","Duration":"1m 29s","ChapterTopicVideoID":27649,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:01.410","Text":"Welcome to acids, bases,"},{"Start":"00:01.410 ","End":"00:03.795","Text":"and pKa dissociation constants."},{"Start":"00:03.795 ","End":"00:07.320","Text":"Define acids and bases by completing the following statements."},{"Start":"00:07.320 ","End":"00:11.685","Text":"A, acids may be defined as donors, B,"},{"Start":"00:11.685 ","End":"00:14.865","Text":"bases can be defined as, and C,"},{"Start":"00:14.865 ","End":"00:21.340","Text":"a proton donor and its corresponding proton acceptor make up a conjugate pair."},{"Start":"00:21.370 ","End":"00:24.410","Text":"Acids may be defined as what?"},{"Start":"00:24.410 ","End":"00:31.980","Text":"Generally, we saw acids can be written like this, etc."},{"Start":"00:31.980 ","End":"00:35.990","Text":"The thing in common is this proton."},{"Start":"00:35.990 ","End":"00:40.940","Text":"Can we say then that acids may be defined as proton donors?"},{"Start":"00:40.940 ","End":"00:45.035","Text":"Now bases can be defined as what happens."},{"Start":"00:45.035 ","End":"00:51.200","Text":"They absorb this, they take on this proton."},{"Start":"00:51.200 ","End":"00:54.350","Text":"Let\u0027s talk about sodium hydroxide,"},{"Start":"00:54.350 ","End":"00:59.000","Text":"NaOH that can be used as a basis for titration or whatever."},{"Start":"00:59.000 ","End":"01:00.680","Text":"You have the hydroxide,"},{"Start":"01:00.680 ","End":"01:08.240","Text":"it will take the proton that\u0027s been donated and becomes H_2O."},{"Start":"01:08.240 ","End":"01:12.725","Text":"So bases can be defined as proton acceptors."},{"Start":"01:12.725 ","End":"01:19.145","Text":"Now, you take a proton donor and its corresponding proton acceptor,"},{"Start":"01:19.145 ","End":"01:24.599","Text":"and you make a conjugate pair of what?"},{"Start":"01:24.850 ","End":"01:28.320","Text":"An acid-base pair."}],"ID":29362},{"Watched":false,"Name":"Exercise 14","Duration":"1m 22s","ChapterTopicVideoID":27650,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.850","Text":"Hi there. We\u0027re within water,"},{"Start":"00:02.850 ","End":"00:04.200","Text":"talking about acids, bases,"},{"Start":"00:04.200 ","End":"00:06.450","Text":"and pKa dissociation constants and"},{"Start":"00:06.450 ","End":"00:09.330","Text":"specifically testing our knowledge on the lesson that we have."},{"Start":"00:09.330 ","End":"00:12.870","Text":"Strong acids and bases have a similarity as do"},{"Start":"00:12.870 ","End":"00:17.115","Text":"weak acids and bases with regard to aqueous solutions. Expand on this."},{"Start":"00:17.115 ","End":"00:20.295","Text":"We\u0027re talking about strong acids and bases that have a similarity,"},{"Start":"00:20.295 ","End":"00:22.905","Text":"and weak acids and bases."},{"Start":"00:22.905 ","End":"00:25.350","Text":"Answer. Hydrochloric, sulfuric,"},{"Start":"00:25.350 ","End":"00:28.545","Text":"and nitric acids are examples of strong acids"},{"Start":"00:28.545 ","End":"00:32.235","Text":"which completely ionize in dilute aqueous solution."},{"Start":"00:32.235 ","End":"00:34.635","Text":"This means that they completely,"},{"Start":"00:34.635 ","End":"00:39.120","Text":"we talked about hydrochloric, separate into,"},{"Start":"00:39.120 ","End":"00:46.590","Text":"they\u0027re ionized into their ions in dilute aqueous solutions."},{"Start":"00:46.590 ","End":"00:51.290","Text":"Strong bases such as sodium hydroxide and potassium hydroxide,"},{"Start":"00:51.290 ","End":"00:54.750","Text":"KOH, are also completely ionized in dilute aqueous solution,"},{"Start":"00:54.750 ","End":"00:56.255","Text":"so in a similar fashion,"},{"Start":"00:56.255 ","End":"01:01.260","Text":"you can also say the NaOH or KOH would"},{"Start":"01:01.260 ","End":"01:06.605","Text":"completely dissociate to become an ionic form."},{"Start":"01:06.605 ","End":"01:11.195","Text":"On the other hand, weak acid and bases do not completely ionize when dissolved in water."},{"Start":"01:11.195 ","End":"01:18.235","Text":"They tend to have this back and forth in this whole dissociation reassociation."},{"Start":"01:18.235 ","End":"01:23.159","Text":"These are common biological systems and play important roles."}],"ID":29363},{"Watched":false,"Name":"Exercise 15","Duration":"3m 49s","ChapterTopicVideoID":27651,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.680","Text":"Hi there. Let\u0027s see if you can answer this question regarding acids,"},{"Start":"00:04.680 ","End":"00:07.770","Text":"bases, and pKa dissociation constants."},{"Start":"00:07.770 ","End":"00:12.075","Text":"Part 1, explain a titration curve and it\u0027s function."},{"Start":"00:12.075 ","End":"00:17.190","Text":"Titration curves are used to determine the amount of an acid in a given solution."},{"Start":"00:17.190 ","End":"00:20.010","Text":"How is this done? The acid is titrated with"},{"Start":"00:20.010 ","End":"00:23.460","Text":"a solution of a strong base usually sodium hydroxide,"},{"Start":"00:23.460 ","End":"00:25.950","Text":"NaOH of known concentration,"},{"Start":"00:25.950 ","End":"00:28.380","Text":"so this is added in increments."},{"Start":"00:28.380 ","End":"00:33.898","Text":"The base NaOH is added in small increments until the acid is consumed,"},{"Start":"00:33.898 ","End":"00:37.910","Text":"neutralized as determined with an indicator dye or"},{"Start":"00:37.910 ","End":"00:44.155","Text":"a pH meter so it will reach about 7 because that is the neutral pH."},{"Start":"00:44.155 ","End":"00:47.780","Text":"The concentration of the acid in the original solution can be calculated"},{"Start":"00:47.780 ","End":"00:51.310","Text":"from the volume and concentration of the sodium hydroxide added."},{"Start":"00:51.310 ","End":"00:57.169","Text":"The amount of base that needed to be added in order to neutralize the acid"},{"Start":"00:57.169 ","End":"01:04.555","Text":"gives an indication as to the concentration of the acid."},{"Start":"01:04.555 ","End":"01:10.805","Text":"Part 2, how does the titration curve relate to pKa and explain with an example?"},{"Start":"01:10.805 ","End":"01:15.310","Text":"pKa is analogous to pH and is defined by the equation"},{"Start":"01:15.310 ","End":"01:22.410","Text":"K_a = log of 1 over K_a and that equals the negative log of K_a."},{"Start":"01:22.410 ","End":"01:27.065","Text":"The stronger the acid is stronger tendency to dissociate a proton,"},{"Start":"01:27.065 ","End":"01:29.410","Text":"the lower it\u0027s pK."},{"Start":"01:29.410 ","End":"01:31.790","Text":"If you have a stronger acid,"},{"Start":"01:31.790 ","End":"01:39.620","Text":"it will dissociate to it\u0027s ions meaning it is dissociating the proton,"},{"Start":"01:39.620 ","End":"01:43.130","Text":"donating it, and it has a lower pKa."},{"Start":"01:43.130 ","End":"01:47.060","Text":"Now a plot of pH against the amount of sodium hydroxide added"},{"Start":"01:47.060 ","End":"01:51.230","Text":"a titration curve reveals the pKa of the weak acid."},{"Start":"01:51.230 ","End":"01:56.795","Text":"Consider the titration of 0.1 molar solution of acidic acid for simplicity,"},{"Start":"01:56.795 ","End":"02:04.110","Text":"denoted as HAc with 0.1 molars NaOH at 25 degrees Celsius."},{"Start":"02:04.110 ","End":"02:08.270","Text":"At the beginning of the titration the acidic acid is slightly ionized"},{"Start":"02:08.270 ","End":"02:12.695","Text":"to an extent that can be calculated from it\u0027s dissociation constant K_a equals,"},{"Start":"02:12.695 ","End":"02:18.095","Text":"the products over the reactants, the ionized product,"},{"Start":"02:18.095 ","End":"02:22.205","Text":"the dissociated product H plus Ac minus,"},{"Start":"02:22.205 ","End":"02:25.010","Text":"and the acidic acid HAc,"},{"Start":"02:25.010 ","End":"02:29.810","Text":"dissociation constant being 1.74 times 10 to the power of 5."},{"Start":"02:29.810 ","End":"02:31.295","Text":"If you look in here,"},{"Start":"02:31.295 ","End":"02:36.350","Text":"we have the CH_3COOH was just the acidic acid,"},{"Start":"02:36.350 ","End":"02:39.230","Text":"and at the beginning it\u0027s slightly ionized."},{"Start":"02:39.230 ","End":"02:41.600","Text":"NaOH is introduced sodium hydroxide."},{"Start":"02:41.600 ","End":"02:44.990","Text":"The added OH minus hydroxide ion"},{"Start":"02:44.990 ","End":"02:49.130","Text":"combines with the free hydrogen ion in the solution to form H_2O."},{"Start":"02:49.130 ","End":"02:50.975","Text":"While this is happening,"},{"Start":"02:50.975 ","End":"02:54.950","Text":"you\u0027re finding that the solution is becoming less and less acidic and"},{"Start":"02:54.950 ","End":"03:00.110","Text":"more and more water molecules make it closer to the neutral as the pH is increasing."},{"Start":"03:00.110 ","End":"03:02.270","Text":"As NaOH is titrated,"},{"Start":"03:02.270 ","End":"03:05.180","Text":"you see the curve going up because"},{"Start":"03:05.180 ","End":"03:08.510","Text":"the pH is increasing and becoming less acidic and then you"},{"Start":"03:08.510 ","End":"03:11.750","Text":"get this midpoint buffering region until you get to"},{"Start":"03:11.750 ","End":"03:15.365","Text":"7 and that is the neutralization spot."},{"Start":"03:15.365 ","End":"03:18.540","Text":"Where the pH is neutral,"},{"Start":"03:18.540 ","End":"03:24.680","Text":"you have the same concentration or molarity of acid and base,"},{"Start":"03:24.680 ","End":"03:26.960","Text":"therefore it is neutral."},{"Start":"03:26.960 ","End":"03:32.240","Text":"This happens to an extent that satisfies the equilibrium relationship in equation"},{"Start":"03:32.240 ","End":"03:37.125","Text":"K_w equals the 2 concentration of the products,"},{"Start":"03:37.125 ","End":"03:39.960","Text":"and that equals 1 times 10 to the negative 14, M^2."},{"Start":"03:39.960 ","End":"03:46.065","Text":"Remember each one if they\u0027re equal can be 10 to the negative 7 but together,"},{"Start":"03:46.065 ","End":"03:48.970","Text":"this is where it stands."}],"ID":29364},{"Watched":false,"Name":"Exercise 16","Duration":"1m 28s","ChapterTopicVideoID":27652,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.120","Text":"Hi there, we have another exercise about acids,"},{"Start":"00:03.120 ","End":"00:05.640","Text":"bases, and pKa dissociation constants."},{"Start":"00:05.640 ","End":"00:08.395","Text":"Which does the midpoint of the titration curve signify?"},{"Start":"00:08.395 ","End":"00:11.610","Text":"The midpoint of the titration curve is where exactly 0.5 of"},{"Start":"00:11.610 ","End":"00:15.630","Text":"the original acidic acid or whatever acid it is has undergone"},{"Start":"00:15.630 ","End":"00:19.050","Text":"dissociation by the titrated equivalent of"},{"Start":"00:19.050 ","End":"00:23.265","Text":"half of the sodium hydroxide or whatever base that\u0027s being used to titrate,"},{"Start":"00:23.265 ","End":"00:25.955","Text":"so that the concentration of the proton donor,"},{"Start":"00:25.955 ","End":"00:27.736","Text":"which is the acid, in this case,"},{"Start":"00:27.736 ","End":"00:29.240","Text":"acidic acid HAc,"},{"Start":"00:29.240 ","End":"00:32.720","Text":"now equals that of the proton acceptor Ac minus."},{"Start":"00:32.720 ","End":"00:35.090","Text":"If we use the example of acetic acid and acetate,"},{"Start":"00:35.090 ","End":"00:37.160","Text":"the midpoint of the titration is where half of"},{"Start":"00:37.160 ","End":"00:40.580","Text":"the original acidic acid has undergone dissociation,"},{"Start":"00:40.580 ","End":"00:44.330","Text":"so that the concentration of the proton donor equals the acceptor."},{"Start":"00:44.330 ","End":"00:47.715","Text":"At this midpoint, a very important relationship holds."},{"Start":"00:47.715 ","End":"00:49.310","Text":"If you\u0027re seeing here,"},{"Start":"00:49.310 ","End":"00:53.660","Text":"the pH of the acetic acid and acetate is equal to the pKa of acetic acid."},{"Start":"00:53.660 ","End":"00:58.710","Text":"Pka is 4.76, and it gives us the buffering region."},{"Start":"00:58.710 ","End":"01:00.260","Text":"The titration is continued."},{"Start":"01:00.260 ","End":"01:04.980","Text":"The remaining acidic acid is gradually converted into acetate."},{"Start":"01:05.020 ","End":"01:09.725","Text":"So CH_3COOH is donating the protons and it is slowly,"},{"Start":"01:09.725 ","End":"01:14.210","Text":"gradually converted into acetate, CH_3COO-."},{"Start":"01:14.210 ","End":"01:17.390","Text":"The endpoint of the titration occurs at around pH 7."},{"Start":"01:17.390 ","End":"01:20.780","Text":"That\u0027s where they are equal and neutralize each other."},{"Start":"01:20.780 ","End":"01:27.900","Text":"So all of acetic acid has lost its protons to OH minus to form H_2O and acetate."}],"ID":29365},{"Watched":false,"Name":"Exercise 17","Duration":"2m 44s","ChapterTopicVideoID":27653,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.820","Text":"Hi, welcome to acids bases,"},{"Start":"00:02.820 ","End":"00:04.920","Text":"and pKa dissociation constants."},{"Start":"00:04.920 ","End":"00:07.800","Text":"We\u0027re testing our knowledge on the lesson we covered."},{"Start":"00:07.800 ","End":"00:09.990","Text":"Explain what can be observed in the figure below"},{"Start":"00:09.990 ","End":"00:12.810","Text":"depicting the titration curves of 3 acids."},{"Start":"00:12.810 ","End":"00:16.140","Text":"If you look here, you have titration curve of 3 acids,"},{"Start":"00:16.140 ","End":"00:19.695","Text":"you have CH_3COOH,"},{"Start":"00:19.695 ","End":"00:22.575","Text":"you have H_2PO_4,"},{"Start":"00:22.575 ","End":"00:25.615","Text":"and you have NH_4+."},{"Start":"00:25.615 ","End":"00:28.110","Text":"The figure compares the titration curves of"},{"Start":"00:28.110 ","End":"00:32.955","Text":"3 weak acids with very different dissociation constants."},{"Start":"00:32.955 ","End":"00:36.030","Text":"Remember, a weak acid means it contributes a proton,"},{"Start":"00:36.030 ","End":"00:39.900","Text":"but doesn\u0027t completely dissociate in solution,"},{"Start":"00:39.900 ","End":"00:42.855","Text":"aqueous solution as do strong acids."},{"Start":"00:42.855 ","End":"00:46.700","Text":"Acetic acid, the first one as you get to see here is the lowest,"},{"Start":"00:46.700 ","End":"00:48.740","Text":"very similar parallel curves shapes,"},{"Start":"00:48.740 ","End":"00:51.940","Text":"but its pKa is 4.76,"},{"Start":"00:51.940 ","End":"00:56.090","Text":"meaning it donates the proton more readily than some of the other ones."},{"Start":"00:56.090 ","End":"01:01.550","Text":"Dihydrogen phosphate H_2PO_4 has a pKa that is somewhat higher than"},{"Start":"01:01.550 ","End":"01:08.400","Text":"acetic acid and it\u0027s close to neutral 7, it is 6.86."},{"Start":"01:08.400 ","End":"01:14.705","Text":"If you see here it\u0027s a little above that of acetic acid."},{"Start":"01:14.705 ","End":"01:17.060","Text":"Then we have our third example,"},{"Start":"01:17.060 ","End":"01:19.205","Text":"ammonium ion NH_4+,"},{"Start":"01:19.205 ","End":"01:23.800","Text":"see at the top it has a high pKa, 9.25."},{"Start":"01:23.800 ","End":"01:28.595","Text":"These 3 curves show you similar behavior,"},{"Start":"01:28.595 ","End":"01:30.125","Text":"yet different pKas,"},{"Start":"01:30.125 ","End":"01:34.010","Text":"different tendencies of donating hydrogens."},{"Start":"01:34.010 ","End":"01:36.580","Text":"Acetic acid with the highest Ka,"},{"Start":"01:36.580 ","End":"01:41.500","Text":"lowest pKa of the 3 is the strongest."},{"Start":"01:41.500 ","End":"01:45.320","Text":"It loses its proton most readily."},{"Start":"01:45.320 ","End":"01:53.250","Text":"We have the pKa because remember that is the log pKa for acetic acid are the lowest."},{"Start":"01:53.250 ","End":"01:57.350","Text":"This means that half of it is dissociated pH 4.76,"},{"Start":"01:57.350 ","End":"01:59.030","Text":"that is the midpoint,"},{"Start":"01:59.030 ","End":"02:01.955","Text":"the rank that we also referred to as the buffer range."},{"Start":"02:01.955 ","End":"02:04.180","Text":"That is where it is somewhat equal,"},{"Start":"02:04.180 ","End":"02:07.535","Text":"half of the acetic acid is dissociated."},{"Start":"02:07.535 ","End":"02:09.485","Text":"If we look at the hydrogen phosphate,"},{"Start":"02:09.485 ","End":"02:14.705","Text":"it loses a proton less readily because it has a higher pKa."},{"Start":"02:14.705 ","End":"02:19.160","Text":"It\u0027s half dissociated at pH 6.86,"},{"Start":"02:19.160 ","End":"02:22.685","Text":"meaning more needed to be added in"},{"Start":"02:22.685 ","End":"02:27.810","Text":"order for the neutralization to occur and reach the buffer region."},{"Start":"02:27.810 ","End":"02:29.520","Text":"Now, as for ammonium ion,"},{"Start":"02:29.520 ","End":"02:31.965","Text":"it is the weakest acid of 3,"},{"Start":"02:31.965 ","End":"02:34.920","Text":"and we see that with the highest pKa,"},{"Start":"02:34.920 ","End":"02:41.340","Text":"half dissociated this ammonium ion in a pH of 9.25."},{"Start":"02:41.340 ","End":"02:44.970","Text":"Significantly higher than all the other ones."}],"ID":29366},{"Watched":false,"Name":"Exercise 18","Duration":"1m 47s","ChapterTopicVideoID":27654,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.840","Text":"Welcome to another exercise within the topic and session of acids,"},{"Start":"00:03.840 ","End":"00:06.735","Text":"bases and pKa, dissociation constants."},{"Start":"00:06.735 ","End":"00:08.595","Text":"Which statement is false?"},{"Start":"00:08.595 ","End":"00:11.070","Text":"Acids donate hydrogen ions, H^+,"},{"Start":"00:11.070 ","End":"00:13.935","Text":"bases donate hydroxide ions, OH^-."},{"Start":"00:13.935 ","End":"00:18.195","Text":"B, both addition of bases and acids can change the pH of a solution."},{"Start":"00:18.195 ","End":"00:21.810","Text":"C, acids and bases will not neutralize each other."},{"Start":"00:21.810 ","End":"00:26.260","Text":"D, acids and bases can mix together."},{"Start":"00:26.870 ","End":"00:30.530","Text":"Acids donate hydrogen ions H^+."},{"Start":"00:30.530 ","End":"00:33.110","Text":"Yes, we can agree that that is true."},{"Start":"00:33.110 ","End":"00:36.770","Text":"Bases donate hydroxide ions OH^-."},{"Start":"00:36.770 ","End":"00:46.355","Text":"We can consider them as donating OH^- or as accepting the hydrogen ions."},{"Start":"00:46.355 ","End":"00:48.440","Text":"This sounds true."},{"Start":"00:48.440 ","End":"00:50.500","Text":"Let\u0027s go over the next one."},{"Start":"00:50.500 ","End":"00:55.385","Text":"B, both addition of bases and acids can change the pH of a solution."},{"Start":"00:55.385 ","End":"00:58.745","Text":"The more acid you add, the pH decreases."},{"Start":"00:58.745 ","End":"01:00.620","Text":"So this is a true statement therefore,"},{"Start":"01:00.620 ","End":"01:04.640","Text":"it can\u0027t be our statement as we want a false one."},{"Start":"01:04.640 ","End":"01:07.565","Text":"Acids and bases will not neutralize each other."},{"Start":"01:07.565 ","End":"01:09.470","Text":"Well, when we look at the titration curve,"},{"Start":"01:09.470 ","End":"01:12.980","Text":"we said the end of the titration curve,"},{"Start":"01:12.980 ","End":"01:16.580","Text":"you had added enough base to neutralize the acid."},{"Start":"01:16.580 ","End":"01:18.560","Text":"If you continue adding base at that point,"},{"Start":"01:18.560 ","End":"01:21.720","Text":"it\u0027s no longer associating the acid and neutralizing."},{"Start":"01:21.720 ","End":"01:24.350","Text":"This sounds like it may be the correct answer,"},{"Start":"01:24.350 ","End":"01:28.265","Text":"but let\u0027s just go to D. Acids and bases can mix together."},{"Start":"01:28.265 ","End":"01:32.240","Text":"Well, of course that\u0027s the whole concept of when we\u0027re doing a titration curve,"},{"Start":"01:32.240 ","End":"01:36.755","Text":"we\u0027re adding a base to the acid to assess the concentration of the acid."},{"Start":"01:36.755 ","End":"01:38.810","Text":"So this can\u0027t be false."},{"Start":"01:38.810 ","End":"01:41.840","Text":"We know it\u0027s true and that leaves us with C. Acids and"},{"Start":"01:41.840 ","End":"01:46.560","Text":"bases will not neutralize each other because yes, they will."}],"ID":29367},{"Watched":false,"Name":"Exercise 19","Duration":"1m 57s","ChapterTopicVideoID":27655,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.540","Text":"Let\u0027s see your proficiency and understanding of acids,"},{"Start":"00:03.540 ","End":"00:06.270","Text":"bases and pKa dissociation constants."},{"Start":"00:06.270 ","End":"00:11.280","Text":"An acidic solution has a high concentration of blank;"},{"Start":"00:11.280 ","End":"00:14.400","Text":"hydroxide ions, hydrogen ions,"},{"Start":"00:14.400 ","End":"00:18.225","Text":"carboxylic aids, or sodium."},{"Start":"00:18.225 ","End":"00:24.270","Text":"If we go back to the definition of acidic solution and how we use various definitions,"},{"Start":"00:24.270 ","End":"00:29.385","Text":"but 1 of them as a proton donor,"},{"Start":"00:29.385 ","End":"00:32.775","Text":"and we said the base is the proton acceptor."},{"Start":"00:32.775 ","End":"00:34.935","Text":"Well, then what is a proton?"},{"Start":"00:34.935 ","End":"00:39.855","Text":"A proton actually being the hydrogen ion,"},{"Start":"00:39.855 ","End":"00:45.695","Text":"the positive most basics small unit and therefore it\u0027s proton."},{"Start":"00:45.695 ","End":"00:49.520","Text":"So an acidic solution has a higher concentration of what?"},{"Start":"00:49.520 ","End":"00:53.190","Text":"Hydroxide ions even though water completely dissociates to it,"},{"Start":"00:53.190 ","End":"00:54.770","Text":"if we think of bases,"},{"Start":"00:54.770 ","End":"00:59.855","Text":"we talk about sodium hydroxide or potassium hydroxide."},{"Start":"00:59.855 ","End":"01:02.180","Text":"When we look at the hydroxide, this,"},{"Start":"01:02.180 ","End":"01:04.940","Text":"in essence, is what makes it a base."},{"Start":"01:04.940 ","End":"01:11.690","Text":"Therefore, I would say this is not the case, not hydroxide ions."},{"Start":"01:11.690 ","End":"01:15.050","Text":"Hydrogen ions, we again mentioned that a second ago."},{"Start":"01:15.050 ","End":"01:21.320","Text":"This is associated with acids. So this makes sense."},{"Start":"01:21.320 ","End":"01:23.515","Text":"It\u0027s what we\u0027ve covered. It\u0027s a proton."},{"Start":"01:23.515 ","End":"01:25.840","Text":"Acids are proton donors."},{"Start":"01:25.840 ","End":"01:27.295","Text":"Let\u0027s move forward."},{"Start":"01:27.295 ","End":"01:32.690","Text":"Carboxylic aids, but we really didn\u0027t talk about this in reference or regard to"},{"Start":"01:32.690 ","End":"01:38.960","Text":"acids and bases and the pH and nor did we specifically talk about sodium."},{"Start":"01:38.960 ","End":"01:41.345","Text":"We talked about sodium hydroxide,"},{"Start":"01:41.345 ","End":"01:44.255","Text":"but not as sodium as an element on its own."},{"Start":"01:44.255 ","End":"01:48.050","Text":"So I would say C is not the correct answer nor is D,"},{"Start":"01:48.050 ","End":"01:49.775","Text":"and it leaves us with B."},{"Start":"01:49.775 ","End":"01:54.230","Text":"An acidic solution has a high concentration of hydrogen ions,"},{"Start":"01:54.230 ","End":"01:57.180","Text":"also known as protons."}],"ID":29368},{"Watched":false,"Name":"Titration Curves, and Buffers Part 1","Duration":"9m 25s","ChapterTopicVideoID":28151,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.600","Text":"Hi there. We\u0027re going to be talking about Titration Curves and Buffers"},{"Start":"00:03.600 ","End":"00:07.970","Text":"within the topic of ionization of water in the chapter on water."},{"Start":"00:07.970 ","End":"00:09.240","Text":"By the end of this section,"},{"Start":"00:09.240 ","End":"00:11.490","Text":"you should be able to define buffers,"},{"Start":"00:11.490 ","End":"00:14.985","Text":"identify and understand the buffering region of a titration curve,"},{"Start":"00:14.985 ","End":"00:17.415","Text":"and use the Henderson-Hasselbach equation."},{"Start":"00:17.415 ","End":"00:19.515","Text":"We\u0027re going to split this into 2 parts."},{"Start":"00:19.515 ","End":"00:22.830","Text":"In Part 1, we will focus on defining buffers and"},{"Start":"00:22.830 ","End":"00:26.370","Text":"identifying and understanding the buffering region of a titration curve."},{"Start":"00:26.370 ","End":"00:29.835","Text":"Almost every biological process is pH-dependent."},{"Start":"00:29.835 ","End":"00:33.840","Text":"A small change in pH produces a large change in the rate of the process."},{"Start":"00:33.840 ","End":"00:36.390","Text":"This is true not only for the many reactions in which"},{"Start":"00:36.390 ","End":"00:39.944","Text":"the H+ the hydrogen ions is a direct participant,"},{"Start":"00:39.944 ","End":"00:44.615","Text":"but also for those in which there is no apparent role for H+ for hydrogen ions."},{"Start":"00:44.615 ","End":"00:49.250","Text":"Enzymes that catalyze cellular reactions and many of the molecules in which they"},{"Start":"00:49.250 ","End":"00:54.304","Text":"act contain ionizable groups with characteristic pKa values."},{"Start":"00:54.304 ","End":"00:56.510","Text":"The protonated amino and carboxyl groups of"},{"Start":"00:56.510 ","End":"00:58.700","Text":"amino acids and the phosphate groups of nucleotides,"},{"Start":"00:58.700 ","End":"01:01.114","Text":"for example, function as weak acids."},{"Start":"01:01.114 ","End":"01:06.200","Text":"Their are ionic state depends on the pH of the surrounding medium."},{"Start":"01:06.200 ","End":"01:09.739","Text":"Ionic interactions are among the forces that stabilize"},{"Start":"01:09.739 ","End":"01:14.705","Text":"a protein molecule and allow an enzyme to recognize and binds its substrate."},{"Start":"01:14.705 ","End":"01:20.495","Text":"Cells and organisms maintain a specific and constant cytosolic pH."},{"Start":"01:20.495 ","End":"01:23.660","Text":"Keeping biomolecules in the optimal ionic state,"},{"Start":"01:23.660 ","End":"01:26.275","Text":"usually near pH 7."},{"Start":"01:26.275 ","End":"01:33.350","Text":"In multicellular organisms, the pH of extracellular fluids is also tightly regulated."},{"Start":"01:33.350 ","End":"01:39.590","Text":"Constancy of pH is achieved primarily by biological buffers,"},{"Start":"01:39.590 ","End":"01:41.090","Text":"mixtures of weak acids,"},{"Start":"01:41.090 ","End":"01:42.560","Text":"and their conjugate bases."},{"Start":"01:42.560 ","End":"01:46.415","Text":"We will understand this term even better after this lesson."},{"Start":"01:46.415 ","End":"01:48.590","Text":"Buffers are aqueous systems,"},{"Start":"01:48.590 ","End":"01:50.810","Text":"remember, water-based systems,"},{"Start":"01:50.810 ","End":"01:56.800","Text":"that resists changes in pH when small amounts of acid,"},{"Start":"01:56.800 ","End":"01:59.755","Text":"H+ or base, OH- are added."},{"Start":"01:59.755 ","End":"02:02.960","Text":"A buffer system consists of weak acid,"},{"Start":"02:02.960 ","End":"02:07.190","Text":"the proton donor, and its conjugate base, the proton acceptor."},{"Start":"02:07.190 ","End":"02:09.545","Text":"This should be familiar from the previous lesson."},{"Start":"02:09.545 ","End":"02:11.450","Text":"As an example, a mixture of"},{"Start":"02:11.450 ","End":"02:15.620","Text":"equal concentrations of acetic acid and acetate ion, as we see here,"},{"Start":"02:15.620 ","End":"02:18.500","Text":"acetic acid and acetate ion,"},{"Start":"02:18.500 ","End":"02:23.120","Text":"found at the midpoint of the titration curve is a buffer system."},{"Start":"02:23.120 ","End":"02:24.410","Text":"As you can see here,"},{"Start":"02:24.410 ","End":"02:26.870","Text":"it\u0027s stating it as being a buffering region."},{"Start":"02:26.870 ","End":"02:32.850","Text":"This is the midpoint and it is when there\u0027s a mixture of equal concentrations of both."},{"Start":"02:32.850 ","End":"02:38.120","Text":"The titration curve of acetic acid has a relatively flat zone,"},{"Start":"02:38.120 ","End":"02:45.115","Text":"extending 1 pH unit on either side of its midpoint pH of 4.76."},{"Start":"02:45.115 ","End":"02:47.830","Text":"If you see here, the midpoint pH is 4.76,"},{"Start":"02:47.830 ","End":"02:49.835","Text":"pH equals the pKa here,"},{"Start":"02:49.835 ","End":"02:51.990","Text":"and it extends about 1 either way,"},{"Start":"02:51.990 ","End":"02:57.330","Text":"376, 576 1 below 476-376,"},{"Start":"02:57.330 ","End":"02:59.100","Text":"and 1 above is 576."},{"Start":"02:59.100 ","End":"03:04.345","Text":"In this zone, an amount of hydrogen ion or hydroxide ion,"},{"Start":"03:04.345 ","End":"03:08.270","Text":"H+ or OH- added to the system has"},{"Start":"03:08.270 ","End":"03:13.350","Text":"much less effect on pH than the same amount added outside the buffer range."},{"Start":"03:13.350 ","End":"03:16.070","Text":"If it was added here or here the same amount,"},{"Start":"03:16.070 ","End":"03:23.120","Text":"it would affect the pH much more than when it is added when it is in the buffer region."},{"Start":"03:23.120 ","End":"03:29.250","Text":"This relatively flat zone is the buffering region of the acetic acid acetate buffer pair."},{"Start":"03:29.250 ","End":"03:30.920","Text":"These act as a pair."},{"Start":"03:30.920 ","End":"03:32.735","Text":"In the middle here,"},{"Start":"03:32.735 ","End":"03:35.660","Text":"this midpoint, they\u0027re equal in concentration."},{"Start":"03:35.660 ","End":"03:41.810","Text":"Acetic acid and acetate or acetate ion equal concentrations in the midpoint where there\u0027s"},{"Start":"03:41.810 ","End":"03:45.170","Text":"this buffering region and these act in"},{"Start":"03:45.170 ","End":"03:49.730","Text":"this buffering region as an acetic acid acetate buffer pair."},{"Start":"03:49.730 ","End":"03:52.130","Text":"At the midpoint of the buffering region,"},{"Start":"03:52.130 ","End":"03:55.880","Text":"where the concentration of the proton donor equals that of the proton acceptor,"},{"Start":"03:55.880 ","End":"03:57.155","Text":"as you can see here,"},{"Start":"03:57.155 ","End":"03:59.359","Text":"they\u0027re said to be equal; the concentrations."},{"Start":"03:59.359 ","End":"04:05.790","Text":"Remember that square brackets signify concentration."},{"Start":"04:05.790 ","End":"04:09.275","Text":"In that midpoint of the buffering region,"},{"Start":"04:09.275 ","End":"04:13.114","Text":"the buffering power of the system is maximum,"},{"Start":"04:13.114 ","End":"04:18.319","Text":"meaning its pH changes least on addition of the acid or base,"},{"Start":"04:18.319 ","End":"04:20.240","Text":"the H+ or OH-."},{"Start":"04:20.240 ","End":"04:24.590","Text":"The pH of the acetate buffer system does change slightly when a small amount"},{"Start":"04:24.590 ","End":"04:28.955","Text":"of H+ or OH- of acid or base is added,"},{"Start":"04:28.955 ","End":"04:31.340","Text":"but this change is very small compared with"},{"Start":"04:31.340 ","End":"04:35.495","Text":"a pH change that would result in the same amount of H+ or OH-"},{"Start":"04:35.495 ","End":"04:39.290","Text":"of acid or base or add it to pure water or to a solution"},{"Start":"04:39.290 ","End":"04:43.114","Text":"of the salt of a strong acid and a strong base such as NaCl,"},{"Start":"04:43.114 ","End":"04:45.695","Text":"sodium chloride, which has no buffering power."},{"Start":"04:45.695 ","End":"04:50.360","Text":"Now, when we\u0027re saying H+ or OH- acid or base,"},{"Start":"04:50.360 ","End":"04:53.840","Text":"we are not saying that we\u0027re actually just adding this."},{"Start":"04:53.840 ","End":"04:56.375","Text":"It could be in the form of HCl."},{"Start":"04:56.375 ","End":"04:58.250","Text":"That would be our acid because,"},{"Start":"04:58.250 ","End":"05:00.500","Text":"upon addition to an aqueous solution,"},{"Start":"05:00.500 ","End":"05:03.740","Text":"it becomes H+ and Cl-."},{"Start":"05:03.740 ","End":"05:07.790","Text":"OH, sodium hydroxide, same idea."},{"Start":"05:07.790 ","End":"05:11.735","Text":"Upon addition to an aqueous solution becomes,"},{"Start":"05:11.735 ","End":"05:13.790","Text":"these are just examples of stronger ones."},{"Start":"05:13.790 ","End":"05:17.750","Text":"Buffering results from 2 reversible reaction equilibria occurring in a solution of"},{"Start":"05:17.750 ","End":"05:23.305","Text":"nearly equal concentrations of a proton donor and its conjugate proton acceptor."},{"Start":"05:23.305 ","End":"05:27.590","Text":"The idea is that there is a reversible reaction going"},{"Start":"05:27.590 ","End":"05:31.730","Text":"between acetic acid and it breaks into"},{"Start":"05:31.730 ","End":"05:35.675","Text":"acetic acid and the proton and acetate"},{"Start":"05:35.675 ","End":"05:41.195","Text":"with accepting or absorbing proton and it dissociating."},{"Start":"05:41.195 ","End":"05:43.340","Text":"These are 2 reversible reactions that"},{"Start":"05:43.340 ","End":"05:46.070","Text":"happen and they have their own equilibria and they occur in"},{"Start":"05:46.070 ","End":"05:49.850","Text":"the solution of these equal concentrations"},{"Start":"05:49.850 ","End":"05:52.670","Text":"of the proton donor and its conjugate proton acceptor."},{"Start":"05:52.670 ","End":"05:59.720","Text":"In this figure, what we see is a visual explanation of how a buffer system works."},{"Start":"05:59.720 ","End":"06:02.870","Text":"H+ or OH- is added to a buffer."},{"Start":"06:02.870 ","End":"06:07.790","Text":"The result is a small change in the ratio of the relative concentrations of"},{"Start":"06:07.790 ","End":"06:13.820","Text":"the weak acid and its anion and thus a small change in pH."},{"Start":"06:13.820 ","End":"06:16.790","Text":"The decrease in concentration of 1 component of"},{"Start":"06:16.790 ","End":"06:20.135","Text":"the system is balanced exactly by an increase in the other."},{"Start":"06:20.135 ","End":"06:25.745","Text":"The sum of the buffer components does not change, only their ratio."},{"Start":"06:25.745 ","End":"06:31.010","Text":"Each conjugate acid pair has a characteristic pH zone in which it is an effective buffer."},{"Start":"06:31.010 ","End":"06:37.520","Text":"The H2PO_4- vs HPO_4 2- pair has a pKa of"},{"Start":"06:37.520 ","End":"06:41.090","Text":"6.86 and thus can serve as an effective buffer system"},{"Start":"06:41.090 ","End":"06:45.130","Text":"between approximately 5.9 and 7.9 pH."},{"Start":"06:45.130 ","End":"06:49.610","Text":"The NH_4+ ammonium versus NH_3 ammonia pair with a pKa of"},{"Start":"06:49.610 ","End":"06:54.740","Text":"9.25 can act as a buffer between approximately 8.3 and 10.3."},{"Start":"06:54.740 ","End":"06:57.110","Text":"You have these buffers with"},{"Start":"06:57.110 ","End":"07:02.315","Text":"their own different pH zones where that is their buffering region."},{"Start":"07:02.315 ","End":"07:06.950","Text":"If we\u0027re looking at the acetic acid acetate pair as buffer system,"},{"Start":"07:06.950 ","End":"07:11.180","Text":"the system is capable of absorbing either H+ or"},{"Start":"07:11.180 ","End":"07:15.710","Text":"OH- through the reversibility of the dissociation of acetic acid,"},{"Start":"07:15.710 ","End":"07:18.740","Text":"the proton donor, which is represented here."},{"Start":"07:18.740 ","End":"07:22.910","Text":"We\u0027ve seen this before in the previous lecture as HAc."},{"Start":"07:22.910 ","End":"07:24.215","Text":"This is acetic acid."},{"Start":"07:24.215 ","End":"07:31.265","Text":"It contains a reserve of bound H+ which can be released to neutralize an addition of OH-."},{"Start":"07:31.265 ","End":"07:33.980","Text":"If OH- is added to the system,"},{"Start":"07:33.980 ","End":"07:41.795","Text":"this reserve hydrogen can combine with the OH- and form H2O, the water molecule."},{"Start":"07:41.795 ","End":"07:44.975","Text":"This happens because the product H+ an OH-"},{"Start":"07:44.975 ","End":"07:50.120","Text":"transiently exceeds the K_w of 1 times 10^-14m^2."},{"Start":"07:50.120 ","End":"07:53.785","Text":"Remember we talked about this in the previous lecture."},{"Start":"07:53.785 ","End":"07:57.785","Text":"This is basically the K_w for water."},{"Start":"07:57.785 ","End":"07:59.810","Text":"When adding one of these,"},{"Start":"07:59.810 ","End":"08:04.085","Text":"there being a transient change in the K_w."},{"Start":"08:04.085 ","End":"08:08.735","Text":"The equilibrium quickly adjusts so that this product equals and goes back"},{"Start":"08:08.735 ","End":"08:14.360","Text":"to this K_w at equilibrium at 25 degrees Celsius,"},{"Start":"08:14.360 ","End":"08:18.410","Text":"thus transiently reducing the concentration of H+."},{"Start":"08:18.410 ","End":"08:20.255","Text":"So you\u0027re taking OH-,"},{"Start":"08:20.255 ","End":"08:25.370","Text":"you\u0027re adding it and it will now have to try to reduce a little bit of the H+ that\u0027s"},{"Start":"08:25.370 ","End":"08:30.800","Text":"been added and it will turn into the water molecule and try to maintain this K_w."},{"Start":"08:30.800 ","End":"08:33.350","Text":"Now the quotient, the concentration of the ions of"},{"Start":"08:33.350 ","End":"08:38.000","Text":"the acetic acid over acetic acid is less than K_w,"},{"Start":"08:38.000 ","End":"08:44.255","Text":"so basically now you need HAc dissociate further to restore equilibrium."},{"Start":"08:44.255 ","End":"08:51.425","Text":"Similarly, the conjugate base Ac- can react with H plus ions added to the system."},{"Start":"08:51.425 ","End":"08:55.135","Text":"Again, the 2 ionization reactions simultaneously come to equilibrium."},{"Start":"08:55.135 ","End":"08:58.280","Text":"These conjugate acid-base pairs such as acetic acid and"},{"Start":"08:58.280 ","End":"09:03.470","Text":"acetate ion tends to resist a change in pH when small amounts of acid or base are added."},{"Start":"09:03.470 ","End":"09:08.450","Text":"Buffering action is simply the consequence of 2 reversible reactions taking place"},{"Start":"09:08.450 ","End":"09:10.940","Text":"simultaneously and reaching their points of"},{"Start":"09:10.940 ","End":"09:15.940","Text":"equilibrium as governed by their equilibrium constants, K_w and K_a."},{"Start":"09:15.940 ","End":"09:20.900","Text":"With this, we completed part 1 of titration curves and buffers and you should be able"},{"Start":"09:20.900 ","End":"09:23.090","Text":"to define buffers on your own and identify"},{"Start":"09:23.090 ","End":"09:26.310","Text":"and understand the buffering region of a titration curve."}],"ID":29369},{"Watched":false,"Name":"Titration Curves, and Buffers Part 2","Duration":"5m 46s","ChapterTopicVideoID":28147,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.500 ","End":"00:05.130","Text":"Hi there. Welcome back to titration curves and buffers."},{"Start":"00:05.130 ","End":"00:07.830","Text":"This is the second part within ionization of water."},{"Start":"00:07.830 ","End":"00:10.800","Text":"In this section, we will focus on relating pH,"},{"Start":"00:10.800 ","End":"00:13.065","Text":"pKa and buffer concentration,"},{"Start":"00:13.065 ","End":"00:15.645","Text":"understanding the Henderson-Hasselbach equation"},{"Start":"00:15.645 ","End":"00:18.510","Text":"and use the Henderson-Hasselbach equation."},{"Start":"00:18.510 ","End":"00:21.480","Text":"It\u0027s simple expression relates pH,"},{"Start":"00:21.480 ","End":"00:24.275","Text":"pKa and buffer concentration."},{"Start":"00:24.275 ","End":"00:29.045","Text":"If you look at the titration curves of acidic acid H_2PO_4 and NH_4,"},{"Start":"00:29.045 ","End":"00:30.860","Text":"they have nearly identical shapes,"},{"Start":"00:30.860 ","End":"00:34.865","Text":"suggesting that these curves reflect a fundamental law or relationship,"},{"Start":"00:34.865 ","End":"00:37.095","Text":"which is indeed the case."},{"Start":"00:37.095 ","End":"00:38.450","Text":"What we mentioned before,"},{"Start":"00:38.450 ","End":"00:39.875","Text":"if you look at these,"},{"Start":"00:39.875 ","End":"00:44.870","Text":"they\u0027re midpoint of the curve where it\u0027s somewhat flat."},{"Start":"00:44.870 ","End":"00:47.195","Text":"This is where it\u0027s relatively flat."},{"Start":"00:47.195 ","End":"00:50.509","Text":"For looking at acidic acid,"},{"Start":"00:50.509 ","End":"00:57.320","Text":"remember up here looking its pH it\u0027s about 4.76,"},{"Start":"00:57.320 ","End":"01:01.295","Text":"so then it\u0027s buffering region is 376-576."},{"Start":"01:01.295 ","End":"01:09.970","Text":"If we are looking now at H_2PO_4- vs H_2PO_42-,"},{"Start":"01:09.970 ","End":"01:12.050","Text":"you see the middle,"},{"Start":"01:12.050 ","End":"01:16.100","Text":"about the midpoint of this plateau."},{"Start":"01:16.100 ","End":"01:18.890","Text":"This flat region is about here,"},{"Start":"01:18.890 ","End":"01:22.715","Text":"and that ends up being about 6.86."},{"Start":"01:22.715 ","End":"01:30.560","Text":"The buffering region of 1 below and 1 above is 6.86, is 586-706."},{"Start":"01:30.560 ","End":"01:34.580","Text":"In this region where acid or base are added,"},{"Start":"01:34.580 ","End":"01:37.855","Text":"it maintains this pH."},{"Start":"01:37.855 ","End":"01:40.625","Text":"Then looking at ammonium and ammonia,"},{"Start":"01:40.625 ","End":"01:44.330","Text":"NH_4 plus and NH_3,"},{"Start":"01:44.330 ","End":"01:50.660","Text":"you see the region, the midpoint here comes up to about here,"},{"Start":"01:50.660 ","End":"01:54.560","Text":"which ends up being like 9.25."},{"Start":"01:54.560 ","End":"01:59.495","Text":"Therefore, the buffer region of that is 8.25 and 10.25."},{"Start":"01:59.495 ","End":"02:04.865","Text":"You\u0027re seeing a similar relationship between all 3"},{"Start":"02:04.865 ","End":"02:10.790","Text":"except that the midpoint is found at a different pH where they have equal amounts,"},{"Start":"02:10.790 ","End":"02:15.515","Text":"where the concentration of the 2 conjugate acid-base pairs are equal,"},{"Start":"02:15.515 ","End":"02:19.640","Text":"it happens at a different pH and therefore they\u0027re buffering region even"},{"Start":"02:19.640 ","End":"02:24.400","Text":"though similar and how it looks as a different pH."},{"Start":"02:24.400 ","End":"02:31.745","Text":"If you look here, this is percent titrated of OH added of the total amount can be added."},{"Start":"02:31.745 ","End":"02:33.890","Text":"This shape of a titration curve of"},{"Start":"02:33.890 ","End":"02:37.894","Text":"any weak acid is described by the Henderson-Hasselbach equation,"},{"Start":"02:37.894 ","End":"02:39.920","Text":"which is important for understanding"},{"Start":"02:39.920 ","End":"02:43.790","Text":"buffer action acid-base balance in the blood and tissues of vertebrates."},{"Start":"02:43.790 ","End":"02:47.840","Text":"This equation is simply a useful way of"},{"Start":"02:47.840 ","End":"02:52.205","Text":"restating the expression for the dissociation constant of an acid."},{"Start":"02:52.205 ","End":"02:57.200","Text":"For the dissociation of a weak acid HA into H+ and"},{"Start":"02:57.200 ","End":"03:06.349","Text":"A- Henderson-Hasselbach equation states that pH equals pKa plus log of A minus over HA."},{"Start":"03:06.349 ","End":"03:08.710","Text":"Or stated more generally,"},{"Start":"03:08.710 ","End":"03:14.945","Text":"pH equals pKa plus log of the proton acceptor or a proton donor."},{"Start":"03:14.945 ","End":"03:19.520","Text":"Proton acceptor, it would generally be our base and"},{"Start":"03:19.520 ","End":"03:24.290","Text":"the proton donor will be our acid HA and A minus,"},{"Start":"03:24.290 ","End":"03:31.525","Text":"if we think of acidic acid HAC, and AC minus."},{"Start":"03:31.525 ","End":"03:34.595","Text":"Now this equation for the titration curve of"},{"Start":"03:34.595 ","End":"03:37.130","Text":"all weak acids and enables"},{"Start":"03:37.130 ","End":"03:39.859","Text":"us to deduce some number of important quantitative relationships."},{"Start":"03:39.859 ","End":"03:43.220","Text":"For example, it shows why the pKa of a weak acid"},{"Start":"03:43.220 ","End":"03:46.940","Text":"is equal to the pH of the solution at the midpoint of its titration."},{"Start":"03:46.940 ","End":"03:48.605","Text":"It at that point,"},{"Start":"03:48.605 ","End":"03:51.925","Text":"HA equals A minus."},{"Start":"03:51.925 ","End":"03:55.295","Text":"If you see the acid and base equal each other,"},{"Start":"03:55.295 ","End":"03:58.805","Text":"the conjugate pair, their concentrations equal each other."},{"Start":"03:58.805 ","End":"04:01.175","Text":"If their concentrations equal each other,"},{"Start":"04:01.175 ","End":"04:02.510","Text":"it means it\u0027s the same,"},{"Start":"04:02.510 ","End":"04:06.570","Text":"so is like saying for just this right here,"},{"Start":"04:06.570 ","End":"04:10.355","Text":"that pKa plus log,"},{"Start":"04:10.355 ","End":"04:14.330","Text":"and we\u0027re just going to save the equal each other."},{"Start":"04:14.330 ","End":"04:16.378","Text":"They are going to be the same,"},{"Start":"04:16.378 ","End":"04:18.710","Text":"you can either say A minus or HA plus,"},{"Start":"04:18.710 ","End":"04:23.930","Text":"A minus equals HA plus A minus for both,"},{"Start":"04:23.930 ","End":"04:26.375","Text":"or it could be HA for both."},{"Start":"04:26.375 ","End":"04:34.410","Text":"Either way. The same number in a fraction divided by itself equals 1,"},{"Start":"04:34.410 ","End":"04:37.375","Text":"so this equals 1."},{"Start":"04:37.375 ","End":"04:43.860","Text":"Therefore, you can now say pH equals pKa plus log 1."},{"Start":"04:43.860 ","End":"04:47.150","Text":"Well, the logarithm of 1 is 0."},{"Start":"04:47.150 ","End":"04:49.415","Text":"If you don\u0027t remember why I put it in your calculator,"},{"Start":"04:49.415 ","End":"04:52.910","Text":"meaning pH equals pKa plus 0."},{"Start":"04:52.910 ","End":"04:56.745","Text":"You can say now pH equals pKa."},{"Start":"04:56.745 ","End":"05:02.300","Text":"That explains why these are the same at this midpoint."},{"Start":"05:02.300 ","End":"05:04.520","Text":"To summarize everything we\u0027ve covered here,"},{"Start":"05:04.520 ","End":"05:07.640","Text":"a mixture of a weak acid or base and its salt resist"},{"Start":"05:07.640 ","End":"05:11.570","Text":"changes in pH caused by the addition of H plus or OH minus,"},{"Start":"05:11.570 ","End":"05:14.420","Text":"meaning acid or base."},{"Start":"05:14.420 ","End":"05:18.125","Text":"The mixture thus functions as a buffer."},{"Start":"05:18.125 ","End":"05:20.060","Text":"The pH of the solution of a weak acid or base and"},{"Start":"05:20.060 ","End":"05:22.430","Text":"itself is given by the Henderson-Hasselbach equation,"},{"Start":"05:22.430 ","End":"05:23.675","Text":"which is what we see here."},{"Start":"05:23.675 ","End":"05:31.489","Text":"pH equals pKa plus log of A minus concentration of A minus over HA."},{"Start":"05:31.489 ","End":"05:33.770","Text":"This is the acid."},{"Start":"05:33.770 ","End":"05:37.235","Text":"Upon completion of titration curves and buffers,"},{"Start":"05:37.235 ","End":"05:39.830","Text":"you should now be able to define buffers,"},{"Start":"05:39.830 ","End":"05:41.960","Text":"identify and understand the buffering region of"},{"Start":"05:41.960 ","End":"05:47.220","Text":"a titration curve and use the Henderson-Hasselbach equation."}],"ID":29370},{"Watched":false,"Name":"Exercise 20","Duration":"1m 16s","ChapterTopicVideoID":27674,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.270","Text":"Hello, we talked about titration curves and buffers,"},{"Start":"00:03.270 ","End":"00:05.550","Text":"and now let\u0027s do some exercises."},{"Start":"00:05.550 ","End":"00:07.500","Text":"Define buffers and their significance."},{"Start":"00:07.500 ","End":"00:09.820","Text":"Buffers are aqueous system, water based,"},{"Start":"00:10.000 ","End":"00:14.340","Text":"that resists changes in pH when small amounts of acid,"},{"Start":"00:14.340 ","End":"00:16.890","Text":"H plus, or base, OH minus, are added."},{"Start":"00:16.890 ","End":"00:19.028","Text":"Buffer system consists of a weak acid,"},{"Start":"00:19.028 ","End":"00:23.415","Text":"the proton donor and its conjugate base, the proton acceptor."},{"Start":"00:23.415 ","End":"00:27.000","Text":"Buffering results from 2 reversible reaction equilibria occurring in"},{"Start":"00:27.000 ","End":"00:30.690","Text":"a solution of nearly equal concentrations of a proton donor,"},{"Start":"00:30.690 ","End":"00:32.805","Text":"and its conjugate, proton acceptor."},{"Start":"00:32.805 ","End":"00:35.640","Text":"Almost every biological process is pH dependent;"},{"Start":"00:35.640 ","End":"00:39.809","Text":"a small change in pH produces a large change in the rate of the processes,"},{"Start":"00:39.809 ","End":"00:45.030","Text":"and this is super crucial in many reactions and situations."},{"Start":"00:45.030 ","End":"00:46.730","Text":"Cells and organisms maintain"},{"Start":"00:46.730 ","End":"00:51.980","Text":"a specific and constant cytosolic pH keeping biomolecules in their optimal ionic state,"},{"Start":"00:51.980 ","End":"00:54.690","Text":"usually near pH 7."},{"Start":"00:54.690 ","End":"00:56.900","Text":"In multicellular organisms, the pH of"},{"Start":"00:56.900 ","End":"01:00.800","Text":"extracellular fluids is also tightly regulated because this also"},{"Start":"01:00.800 ","End":"01:07.340","Text":"affects reactions all around and the state of ions and molecules surrounding the cells."},{"Start":"01:07.340 ","End":"01:12.035","Text":"This constancy of pH is achieved primarily by biological buffers,"},{"Start":"01:12.035 ","End":"01:16.170","Text":"these mixtures of weak acids and their conjugate bases."}],"ID":29371},{"Watched":false,"Name":"Exercise 21","Duration":"4m 2s","ChapterTopicVideoID":27675,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.070","Text":"Hi, welcome back to titration curves and"},{"Start":"00:02.070 ","End":"00:04.590","Text":"buffers as we are testing your knowledge on this."},{"Start":"00:04.590 ","End":"00:06.615","Text":"What is the buffering region?"},{"Start":"00:06.615 ","End":"00:12.075","Text":"Answer. The buffering region is the midpoint of the titration curve."},{"Start":"00:12.075 ","End":"00:15.390","Text":"That flat zone, if you remember from this figure,"},{"Start":"00:15.390 ","End":"00:20.170","Text":"that is extending about 1 pH unit on either side of its midpoint pH."},{"Start":"00:20.170 ","End":"00:24.810","Text":"This is the midpoint pH where it\u0027s also equal to pKa and"},{"Start":"00:24.810 ","End":"00:30.150","Text":"1 pH above and below is the buffering region."},{"Start":"00:30.150 ","End":"00:33.810","Text":"In this zone an amount of H+ or OH- added to"},{"Start":"00:33.810 ","End":"00:36.390","Text":"the system has much less effect"},{"Start":"00:36.390 ","End":"00:39.130","Text":"on the pH than the same amount added outside buffer range."},{"Start":"00:39.130 ","End":"00:47.270","Text":"If we add x amount of H+ in this region versus if we add it over here,"},{"Start":"00:47.270 ","End":"00:51.890","Text":"we will see here a greater change in the pH."},{"Start":"00:51.890 ","End":"00:55.370","Text":"It will reduce much more than when here,"},{"Start":"00:55.370 ","End":"00:56.960","Text":"because if you just look by points,"},{"Start":"00:56.960 ","End":"00:58.385","Text":"how much is added."},{"Start":"00:58.385 ","End":"01:01.610","Text":"When you see here, it remains similar pH,"},{"Start":"01:01.610 ","End":"01:06.095","Text":"this pH versus this pH versus this pH,"},{"Start":"01:06.095 ","End":"01:09.160","Text":"they\u0027re all above 4, so this would be,"},{"Start":"01:09.160 ","End":"01:14.050","Text":"let\u0027s say 4.2 and this would be 4.3,"},{"Start":"01:14.050 ","End":"01:15.670","Text":"and this would be 4.4."},{"Start":"01:15.670 ","End":"01:20.465","Text":"Whereas here, the same amount of OH minus added,"},{"Start":"01:20.465 ","End":"01:26.900","Text":"you\u0027ll have a jump that it goes from 3 to more like 3.6."},{"Start":"01:26.900 ","End":"01:29.675","Text":"Or if you have here where you\u0027re adding,"},{"Start":"01:29.675 ","End":"01:31.145","Text":"for example H,"},{"Start":"01:31.145 ","End":"01:35.250","Text":"you will see a drop from 3-2."},{"Start":"01:35.250 ","End":"01:41.000","Text":"The changes are much smaller in the buffering region because it is"},{"Start":"01:41.000 ","End":"01:47.500","Text":"that point where it\u0027s that flat region of the titration curve."},{"Start":"01:47.500 ","End":"01:50.900","Text":"At the midpoint of the buffering region where the concentration of"},{"Start":"01:50.900 ","End":"01:55.320","Text":"the proton donor exactly equals that of the proton acceptor,"},{"Start":"01:55.320 ","End":"01:58.010","Text":"in this figure we\u0027re talking about acetate,"},{"Start":"01:58.010 ","End":"02:01.220","Text":"the buffering power of the system is maximal,"},{"Start":"02:01.220 ","End":"02:07.345","Text":"meaning it\u0027s pH changes at least on addition of H plus or OH minus of acid or base."},{"Start":"02:07.345 ","End":"02:10.760","Text":"Here you see at this midpoint,"},{"Start":"02:10.760 ","End":"02:14.090","Text":"the concentrations of the 2 are equal,"},{"Start":"02:14.090 ","End":"02:15.335","Text":"the acid and the base."},{"Start":"02:15.335 ","End":"02:21.400","Text":"The pH point at this point in the titration curve is equal to its pKa."},{"Start":"02:21.400 ","End":"02:24.410","Text":"The pH of the acetate buffer system does change"},{"Start":"02:24.410 ","End":"02:27.140","Text":"slightly when a small amount of H+ or OH- is added."},{"Start":"02:27.140 ","End":"02:30.005","Text":"But this change is very small compared with the pH change that would"},{"Start":"02:30.005 ","End":"02:33.120","Text":"result with the same amount of H+ or OH- were"},{"Start":"02:33.120 ","End":"02:35.390","Text":"added to pure water or to a solution of"},{"Start":"02:35.390 ","End":"02:39.395","Text":"the salt of a strong acid and strong base such as sodium chloride,"},{"Start":"02:39.395 ","End":"02:41.855","Text":"NaCl, which has no buffering power."},{"Start":"02:41.855 ","End":"02:49.340","Text":"Each conjugate acid pair has a characteristic pH zone in which is an effective buffer."},{"Start":"02:49.340 ","End":"02:54.635","Text":"If we look here, the H_2PO_4 versus HPO_4^2 buffer."},{"Start":"02:54.635 ","End":"02:58.550","Text":"These here, they have a pKa of 6.86,"},{"Start":"02:58.550 ","End":"03:02.370","Text":"that\u0027s higher than the pKa of acidic acid and acetate."},{"Start":"03:02.370 ","End":"03:07.190","Text":"For H_2PO_4^2 minus consider an effective buffer system"},{"Start":"03:07.190 ","End":"03:11.960","Text":"between approximately 5.9 and 7.9,"},{"Start":"03:11.960 ","End":"03:14.795","Text":"so 5.86 and 7.86."},{"Start":"03:14.795 ","End":"03:22.265","Text":"The ammonia ammonium conjugate acid-base pair have a pKa of 9.25 much higher,"},{"Start":"03:22.265 ","End":"03:23.570","Text":"much more basic,"},{"Start":"03:23.570 ","End":"03:25.595","Text":"and this can act as a buffer, thus,"},{"Start":"03:25.595 ","End":"03:32.525","Text":"between approximately 8.25-10.25 or let\u0027s say 8.3-10.3."},{"Start":"03:32.525 ","End":"03:34.955","Text":"Now, having these different buffering regions"},{"Start":"03:34.955 ","End":"03:38.720","Text":"is beneficial also knowing them because if we do"},{"Start":"03:38.720 ","End":"03:45.500","Text":"want to test things and try out things and you want different pH regions,"},{"Start":"03:45.500 ","End":"03:48.020","Text":"you need to add things that are way more acidic,"},{"Start":"03:48.020 ","End":"03:52.545","Text":"you can play and use different buffering systems,"},{"Start":"03:52.545 ","End":"03:54.800","Text":"different conjugate pairs that have"},{"Start":"03:54.800 ","End":"04:02.610","Text":"different buffering regions with their different pH and match it to what your object is."}],"ID":29372},{"Watched":false,"Name":"Exercise 22","Duration":"1m 41s","ChapterTopicVideoID":27676,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.295","Text":"Hi there. We\u0027re talking about"},{"Start":"00:02.295 ","End":"00:06.360","Text":"information we learned in the lesson about titration curves, and buffers."},{"Start":"00:06.360 ","End":"00:11.775","Text":"What can be said according to the lesson about concentrations of the buffer components?"},{"Start":"00:11.775 ","End":"00:14.865","Text":"When H plus or OH minus is added to a buffer,"},{"Start":"00:14.865 ","End":"00:16.230","Text":"talking about acid or base,"},{"Start":"00:16.230 ","End":"00:18.150","Text":"the result is a small change in the ratio of"},{"Start":"00:18.150 ","End":"00:21.315","Text":"the relative concentrations of the weak acid and its anion,"},{"Start":"00:21.315 ","End":"00:23.580","Text":"and thus a small change in pH."},{"Start":"00:23.580 ","End":"00:27.300","Text":"The decrease in concentration of 1 component of the system"},{"Start":"00:27.300 ","End":"00:31.350","Text":"is balanced exactly by an increase in the other."},{"Start":"00:31.350 ","End":"00:36.495","Text":"The sum of the buffer components does not change, only their ratio."},{"Start":"00:36.495 ","End":"00:38.815","Text":"When you add 1,"},{"Start":"00:38.815 ","End":"00:40.970","Text":"either acid or base,"},{"Start":"00:40.970 ","End":"00:47.780","Text":"they will adjust with the interaction with their counterpart and water to"},{"Start":"00:47.780 ","End":"00:51.680","Text":"balance the increase so that the sum of"},{"Start":"00:51.680 ","End":"00:55.610","Text":"the buffer components does not change, only their ratio."},{"Start":"00:55.610 ","End":"00:58.175","Text":"That is when we talked about, for example,"},{"Start":"00:58.175 ","End":"01:02.635","Text":"the Kw of equaling 1 times 10 to the negative 14,"},{"Start":"01:02.635 ","End":"01:04.650","Text":"safe for the dissociation of water or not."},{"Start":"01:04.650 ","End":"01:06.480","Text":"This will remain the same,"},{"Start":"01:06.480 ","End":"01:08.750","Text":"and in order for this to remain the same,"},{"Start":"01:08.750 ","End":"01:12.500","Text":"we said the H plus the equilibrium"},{"Start":"01:12.500 ","End":"01:17.795","Text":"equals OH minus which with each 1 being 10 to the negative 7."},{"Start":"01:17.795 ","End":"01:20.930","Text":"But now if 1 of these increases,"},{"Start":"01:20.930 ","End":"01:23.630","Text":"this will have to decrease."},{"Start":"01:23.630 ","End":"01:27.365","Text":"That together combined,"},{"Start":"01:27.365 ","End":"01:30.650","Text":"the buffer components concentration is 1 times 10 to the"},{"Start":"01:30.650 ","End":"01:34.325","Text":"negative 14 because together sent to the negative 14."},{"Start":"01:34.325 ","End":"01:37.115","Text":"If 1 of them goes up or down,"},{"Start":"01:37.115 ","End":"01:41.520","Text":"the other 1 needs to adjust up or down as well."}],"ID":29373},{"Watched":false,"Name":"Exercise 23","Duration":"1m 36s","ChapterTopicVideoID":27677,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.890 ","End":"00:05.350","Text":"Hey there, let\u0027s test our knowledge on Titration curves and Buffers."},{"Start":"00:05.350 ","End":"00:08.445","Text":"What is the Henderson-Hasselbach equation?"},{"Start":"00:08.445 ","End":"00:10.860","Text":"The shape of the titration curve of any weak acid"},{"Start":"00:10.860 ","End":"00:12.975","Text":"is described by the Henderson-Hasselbach equation,"},{"Start":"00:12.975 ","End":"00:15.360","Text":"which is important for understanding buffer action and"},{"Start":"00:15.360 ","End":"00:17.835","Text":"acid-base balance in the blood and tissues of vertebrates."},{"Start":"00:17.835 ","End":"00:21.090","Text":"This equation is simply a useful way of restating"},{"Start":"00:21.090 ","End":"00:24.930","Text":"the expression for the dissociation constant of an acid,"},{"Start":"00:24.930 ","End":"00:30.830","Text":"for the dissociation of a weak acid HA into H+ and A-."},{"Start":"00:30.830 ","End":"00:39.185","Text":"The Henderson-Hasselbach equation is pH=pKa +log of A- over HA."},{"Start":"00:39.185 ","End":"00:42.800","Text":"To state it in a more general way,"},{"Start":"00:42.800 ","End":"00:49.285","Text":"pH =pKa + log of proton acceptor over proton donor."},{"Start":"00:49.285 ","End":"00:51.915","Text":"The proton acceptor A-,"},{"Start":"00:51.915 ","End":"00:58.750","Text":"that is also our base and the proton donor is the acid HA."},{"Start":"00:58.750 ","End":"01:03.050","Text":"For example, if we talk about acetic acid and acetate,"},{"Start":"01:03.050 ","End":"01:09.680","Text":"acetic acid would be here and acetate would be up top."},{"Start":"01:09.680 ","End":"01:13.250","Text":"Now this equation fits the titration curve of all weak acids and"},{"Start":"01:13.250 ","End":"01:17.255","Text":"enables us to deduce a number of important quantitative relationships."},{"Start":"01:17.255 ","End":"01:20.090","Text":"The Henderson-Hasselbach allows us to calculate"},{"Start":"01:20.090 ","End":"01:24.140","Text":"pKa given pH and the molar ratio of proton donor-acceptor to"},{"Start":"01:24.140 ","End":"01:27.140","Text":"calculate pH given the pKa and the molar ratio of"},{"Start":"01:27.140 ","End":"01:31.655","Text":"proton donor and acceptor and calculate the molar ratio."},{"Start":"01:31.655 ","End":"01:35.820","Text":"A proton donor and acceptor given pH and pKa."}],"ID":29374},{"Watched":false,"Name":"Exercise 24","Duration":"7m 52s","ChapterTopicVideoID":27678,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.758","Text":"We\u0027re back and Titration Curves and Buffers."},{"Start":"00:03.758 ","End":"00:08.880","Text":"We are going to solve some problems using the Henderson-Hasselbalch equation."},{"Start":"00:08.880 ","End":"00:12.450","Text":"Now, we\u0027re actually going to be actively doing some problems."},{"Start":"00:12.450 ","End":"00:15.390","Text":"We have the equation as pH equals pKa"},{"Start":"00:15.390 ","End":"00:19.245","Text":"plus logarithm of a proton acceptor over proton donor."},{"Start":"00:19.245 ","End":"00:25.455","Text":"Just remember that generally this is our base and this is our acid."},{"Start":"00:25.455 ","End":"00:27.225","Text":"Let\u0027s start."},{"Start":"00:27.225 ","End":"00:28.620","Text":"Part I."},{"Start":"00:28.620 ","End":"00:34.590","Text":"Calculate the pKa of lactic acid given that when the concentration of lactic acid is"},{"Start":"00:34.590 ","End":"00:40.640","Text":"0.01M and the concentration of lactate is 0.087M,"},{"Start":"00:40.640 ","End":"00:44.045","Text":"the pH is 4.8."},{"Start":"00:44.045 ","End":"00:46.500","Text":"This could be a little scary. Oh My God."},{"Start":"00:46.500 ","End":"00:49.880","Text":"There\u0027s these things with lactic acid. Doesn\u0027t matter."},{"Start":"00:49.880 ","End":"00:55.430","Text":"We want to calculate the pKa and we were given lactic acid."},{"Start":"00:55.430 ","End":"00:58.940","Text":"We know what is lactic acid, it\u0027s the donor."},{"Start":"00:58.940 ","End":"01:06.815","Text":"We have the concentration of our donor as being 0.01M and we have of lactate."},{"Start":"01:06.815 ","End":"01:11.785","Text":"Lactate, ate, is our base."},{"Start":"01:11.785 ","End":"01:17.940","Text":"We have our acceptor and we are given the pH."},{"Start":"01:17.940 ","End":"01:20.355","Text":"Our pH is 4.8."},{"Start":"01:20.355 ","End":"01:24.980","Text":"Now, this is a mathematical equation where we are given"},{"Start":"01:24.980 ","End":"01:32.105","Text":"these parameters that we can replace and are left to find and solve for pKa."},{"Start":"01:32.105 ","End":"01:34.160","Text":"We write out the equation."},{"Start":"01:34.160 ","End":"01:37.310","Text":"I find it always easier for me to go step by step"},{"Start":"01:37.310 ","End":"01:40.760","Text":"and write everything out because it also drills it into your head,"},{"Start":"01:40.760 ","End":"01:43.310","Text":"because if you are then under pressure and trying to"},{"Start":"01:43.310 ","End":"01:46.190","Text":"go for the exam and you\u0027re a little stressed,"},{"Start":"01:46.190 ","End":"01:48.065","Text":"if you write it out,"},{"Start":"01:48.065 ","End":"01:49.684","Text":"even if you make a mistake,"},{"Start":"01:49.684 ","End":"01:51.350","Text":"you can go back and be like, Oh My God,"},{"Start":"01:51.350 ","End":"01:55.843","Text":"I put acetate as my proton donor and acetic acid as my proton acceptor."},{"Start":"01:55.843 ","End":"01:58.310","Text":"But no. Acid is the donor."},{"Start":"01:58.310 ","End":"02:00.645","Text":"First off, we take the step"},{"Start":"02:00.645 ","End":"02:03.452","Text":"and we replace with information that we\u0027re given in the problem,"},{"Start":"02:03.452 ","End":"02:07.910","Text":"in the question, and we write it out replacing the information here."},{"Start":"02:07.910 ","End":"02:14.670","Text":"I will say pKa plus log of lactate we said"},{"Start":"02:14.670 ","End":"02:24.650","Text":"is 0.087 molar over 0.01 molar for lactic acid."},{"Start":"02:24.650 ","End":"02:30.185","Text":"Now, we want to solve for pKa because we actually have pH which is 4.80."},{"Start":"02:30.185 ","End":"02:32.480","Text":"To solve for pKa,"},{"Start":"02:32.480 ","End":"02:34.745","Text":"we actually want to take this"},{"Start":"02:34.745 ","End":"02:38.570","Text":"algebraically and move it to the other side which means we would"},{"Start":"02:38.570 ","End":"02:47.350","Text":"have pH minus log of our fraction equals pKa."},{"Start":"02:47.350 ","End":"02:57.720","Text":"Now reverse it and move for ease pKa equals our pH minus log of the fraction."},{"Start":"02:57.720 ","End":"03:02.280","Text":"Now if we look we have pKa equals our pH,"},{"Start":"03:02.280 ","End":"03:03.950","Text":"we said is 4.8,"},{"Start":"03:03.950 ","End":"03:07.125","Text":"minus the log of lactate,"},{"Start":"03:07.125 ","End":"03:11.810","Text":"0.087 over lactic acid 0.01."},{"Start":"03:11.810 ","End":"03:13.355","Text":"They are both molars,"},{"Start":"03:13.355 ","End":"03:16.100","Text":"so we no longer have to write it because if we have"},{"Start":"03:16.100 ","End":"03:19.430","Text":"the same they cancel out and then just"},{"Start":"03:19.430 ","End":"03:25.275","Text":"putting it into the calculator or even just looking at the facts that"},{"Start":"03:25.275 ","End":"03:31.505","Text":"it\u0027s 87 divided by 10 because it\u0027s at the same decimal point."},{"Start":"03:31.505 ","End":"03:36.290","Text":"It is 8.7. Again, if this is confusing to you if you just put it in"},{"Start":"03:36.290 ","End":"03:42.155","Text":"a calculator you\u0027ll see that 0.087 over 0.01 is 8.7."},{"Start":"03:42.155 ","End":"03:48.110","Text":"Another way to look at it is like saying 8.7"},{"Start":"03:48.110 ","End":"03:54.745","Text":"times 10 to the negative,"},{"Start":"03:54.745 ","End":"03:57.455","Text":"you have a decimal point 1, 2, negative 2 and the same for here."},{"Start":"03:57.455 ","End":"04:03.105","Text":"We have it would be like saying 1 times 10^negative 2."},{"Start":"04:03.105 ","End":"04:04.695","Text":"This divided by this."},{"Start":"04:04.695 ","End":"04:07.560","Text":"This cancels out and equals 8.7."},{"Start":"04:07.560 ","End":"04:09.170","Text":"If that was confusing don\u0027t worry about it."},{"Start":"04:09.170 ","End":"04:13.850","Text":"It\u0027s just for those of you that like math and want to understand."},{"Start":"04:13.850 ","End":"04:17.110","Text":"If you put it again in a calculator divide it,"},{"Start":"04:17.110 ","End":"04:22.250","Text":"you will get 8.7 and then you are left with 4.8."},{"Start":"04:22.250 ","End":"04:26.080","Text":"That was our pH minus log 8.7."},{"Start":"04:26.080 ","End":"04:32.380","Text":"That\u0027s just solving for the fraction and once you put log 8.7 in the calculator you get"},{"Start":"04:32.380 ","End":"04:37.560","Text":"0.94 and therefore pKa is 4.8 minus"},{"Start":"04:37.560 ","End":"04:43.305","Text":"0.94 and you get your pKa as 3.9."},{"Start":"04:43.305 ","End":"04:45.595","Text":"Let\u0027s go to Part II."},{"Start":"04:45.595 ","End":"04:48.635","Text":"Hopefully now it will be a little bit easier and less scary."},{"Start":"04:48.635 ","End":"04:57.980","Text":"Calculate the pH of a mixture of 0.1M acetic acid and 0.2M sodium acetate."},{"Start":"04:57.980 ","End":"05:02.530","Text":"The pKa_ of acidic acid is 4.76."},{"Start":"05:02.530 ","End":"05:08.100","Text":"Again, if we put these and place them in to our formula,"},{"Start":"05:08.100 ","End":"05:10.220","Text":"pH of the mixture is what we\u0027re going for."},{"Start":"05:10.220 ","End":"05:13.610","Text":"Acetic acid is our proton donor."},{"Start":"05:13.610 ","End":"05:15.220","Text":"This would be down here."},{"Start":"05:15.220 ","End":"05:20.735","Text":"Sodium acetate, that will be our proton acceptor."},{"Start":"05:20.735 ","End":"05:23.380","Text":"Now remember, we said these in"},{"Start":"05:23.380 ","End":"05:26.690","Text":"a fraction in the same units they will cancel each other out."},{"Start":"05:26.690 ","End":"05:32.955","Text":"The pKa that we\u0027re given as 4.76 and now looking at the fraction,"},{"Start":"05:32.955 ","End":"05:36.710","Text":"we can reduce it based on the relationship between the numerator and denominator,"},{"Start":"05:36.710 ","End":"05:39.988","Text":"or take a minute to solve this on the calculator,"},{"Start":"05:39.988 ","End":"05:42.225","Text":"but it\u0027s basically 2 to 1."},{"Start":"05:42.225 ","End":"05:44.495","Text":"As going with we solve with that relationship,"},{"Start":"05:44.495 ","End":"05:49.265","Text":"what it means is that we have 4.76 plus log 2."},{"Start":"05:49.265 ","End":"05:52.160","Text":"I\u0027ll give you a minute to plug log 2 into"},{"Start":"05:52.160 ","End":"05:58.410","Text":"your calculator and you should be getting that it is 0.3,"},{"Start":"05:58.410 ","End":"06:04.469","Text":"so pH=4.76 plus 0.3 and now solving for that,"},{"Start":"06:04.469 ","End":"06:09.120","Text":"taking a minute, pH=5.1."},{"Start":"06:09.120 ","End":"06:15.150","Text":"Just to drill this concept of these calculations into your head, here\u0027s another one."},{"Start":"06:15.150 ","End":"06:19.100","Text":"Calculate the ratio of the concentrations of acetate and acidic acid"},{"Start":"06:19.100 ","End":"06:23.690","Text":"required in a buffer system of pH 5.30."},{"Start":"06:23.690 ","End":"06:30.885","Text":"Now we\u0027re given the pH as 5.3 and we want to solve this ratio."},{"Start":"06:30.885 ","End":"06:33.485","Text":"This is what we are looking for."},{"Start":"06:33.485 ","End":"06:35.405","Text":"But then what about pKa?"},{"Start":"06:35.405 ","End":"06:39.710","Text":"PKa is something that is known for each pair and just to remind you,"},{"Start":"06:39.710 ","End":"06:47.910","Text":"we actually just covered this before but the pKa of acetic acid is 4.76,"},{"Start":"06:47.910 ","End":"06:53.370","Text":"so pKa of acetic acid 4.76."},{"Start":"06:53.370 ","End":"06:56.460","Text":"We can put that here."},{"Start":"06:56.460 ","End":"06:58.160","Text":"How do we isolate log?"},{"Start":"06:58.160 ","End":"07:01.460","Text":"Well, we do an antilog of the other side."},{"Start":"07:01.460 ","End":"07:02.915","Text":"To get rid of the log,"},{"Start":"07:02.915 ","End":"07:05.665","Text":"we want to do an antilog."},{"Start":"07:05.665 ","End":"07:08.795","Text":"If you don\u0027t remember this then trust me on it."},{"Start":"07:08.795 ","End":"07:14.210","Text":"We take this antilog and now we place the 5.3 for the pH,"},{"Start":"07:14.210 ","End":"07:16.265","Text":"the 4.76 for the pKa."},{"Start":"07:16.265 ","End":"07:19.940","Text":"This results in 0.54."},{"Start":"07:19.940 ","End":"07:25.755","Text":"Now we put that here to solve this in your calculator."},{"Start":"07:25.755 ","End":"07:31.010","Text":"Take that minute. Solve it yourself and you should end up"},{"Start":"07:31.010 ","End":"07:36.740","Text":"with the value of the ratio of the proton acceptors to proton donor,"},{"Start":"07:36.740 ","End":"07:39.650","Text":"of the base to acid as being,"},{"Start":"07:39.650 ","End":"07:43.655","Text":"did you put it in your calculator antilog of 0.54?"},{"Start":"07:43.655 ","End":"07:48.030","Text":"You should come up with 3.5."},{"Start":"07:48.030 ","End":"07:53.040","Text":"With this, hopefully you\u0027re not as scared of these calculations anymore."}],"ID":29375},{"Watched":false,"Name":"Exercise 25","Duration":"3m 36s","ChapterTopicVideoID":27679,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.845","Text":"Hey. Welcome back to exercises on titration curves and buffers."},{"Start":"00:04.845 ","End":"00:08.655","Text":"A basic solution has a pH and can be neutralized by?"},{"Start":"00:08.655 ","End":"00:10.170","Text":"Multiple choice."},{"Start":"00:10.170 ","End":"00:12.615","Text":"Let\u0027s go. A basic solution has"},{"Start":"00:12.615 ","End":"00:19.620","Text":"a low pH and can be neutralized by adding more hydrogen ions."},{"Start":"00:19.620 ","End":"00:21.765","Text":"Well, let\u0027s try to think."},{"Start":"00:21.765 ","End":"00:24.975","Text":"Our pH scale from the previous lesson,"},{"Start":"00:24.975 ","End":"00:28.440","Text":"we know that we have our pH scale 1 through 14 with 7 being neutral,"},{"Start":"00:28.440 ","End":"00:32.655","Text":"so is low or high, basic or acidic."},{"Start":"00:32.655 ","End":"00:33.870","Text":"A basic solution,"},{"Start":"00:33.870 ","End":"00:35.355","Text":"is it low or high?"},{"Start":"00:35.355 ","End":"00:37.469","Text":"If it is low,"},{"Start":"00:37.469 ","End":"00:39.195","Text":"what would neutralize it?"},{"Start":"00:39.195 ","End":"00:43.865","Text":"Our hydrogen ions, are they acid or base?"},{"Start":"00:43.865 ","End":"00:46.730","Text":"Let\u0027s give you a little hint."},{"Start":"00:46.730 ","End":"00:48.590","Text":"This is the hydrogen ion."},{"Start":"00:48.590 ","End":"00:50.030","Text":"Not going to say anything else."},{"Start":"00:50.030 ","End":"00:51.650","Text":"We\u0027re going to move forward to b."},{"Start":"00:51.650 ","End":"01:00.200","Text":"A basic solution has a high pH and can be neutralized by adding more hydroxide ions."},{"Start":"01:00.200 ","End":"01:02.750","Text":"Hydroxide ions."},{"Start":"01:02.750 ","End":"01:05.435","Text":"Again, acid or base."},{"Start":"01:05.435 ","End":"01:11.270","Text":"Do we remember our acid or base is high or low?"},{"Start":"01:11.270 ","End":"01:15.800","Text":"Let\u0027s go to c. A basic solution has a low pH and can be"},{"Start":"01:15.800 ","End":"01:20.614","Text":"neutralized by removing hydrogen ions."},{"Start":"01:20.614 ","End":"01:24.625","Text":"Removing these hydrogen ions."},{"Start":"01:24.625 ","End":"01:27.845","Text":"Now let\u0027s talk about d. A basic solution has"},{"Start":"01:27.845 ","End":"01:35.170","Text":"a high pH and can be neutralized by removing hydroxide ions."},{"Start":"01:35.170 ","End":"01:39.450","Text":"Last but not least, none of the above."},{"Start":"01:39.450 ","End":"01:43.835","Text":"The lower end of the pH scale is actually acidic"},{"Start":"01:43.835 ","End":"01:49.370","Text":"giving the high end the alkali basic side."},{"Start":"01:49.370 ","End":"01:51.785","Text":"If we have a basic solution,"},{"Start":"01:51.785 ","End":"01:54.440","Text":"the pH would be high."},{"Start":"01:54.440 ","End":"02:01.100","Text":"We can eliminate a and c. This leaves us with b,"},{"Start":"02:01.100 ","End":"02:05.630","Text":"d, or e. A basic solution has a high pH."},{"Start":"02:05.630 ","End":"02:08.300","Text":"What can neutralize a base?"},{"Start":"02:08.300 ","End":"02:12.290","Text":"A base can be neutralized by an acid."},{"Start":"02:12.290 ","End":"02:15.215","Text":"If we have hydroxide,"},{"Start":"02:15.215 ","End":"02:20.525","Text":"OH-, is that a base or an acid or hydrogen?"},{"Start":"02:20.525 ","End":"02:27.470","Text":"Well, OH is our representation of a base whereas H+ is our acid."},{"Start":"02:27.470 ","End":"02:30.290","Text":"If we have a high basic solution,"},{"Start":"02:30.290 ","End":"02:32.935","Text":"a high pH, what would we want to add?"},{"Start":"02:32.935 ","End":"02:34.955","Text":"We want to get it to be neutral,"},{"Start":"02:34.955 ","End":"02:41.825","Text":"we need to lower the pH which means we actually need to add something acidic."},{"Start":"02:41.825 ","End":"02:46.205","Text":"Adding an H plus would be better versus adding more base because"},{"Start":"02:46.205 ","End":"02:51.390","Text":"adding more base should result in our pH going even higher."},{"Start":"02:51.390 ","End":"02:55.095","Text":"It can\u0027t be adding more base."},{"Start":"02:55.095 ","End":"03:00.560","Text":"Now, can we remove hydroxide ions and basically remove"},{"Start":"03:00.560 ","End":"03:06.950","Text":"base from this and therefore somewhat neutralize it?"},{"Start":"03:06.950 ","End":"03:10.265","Text":"In theory, that could be correct."},{"Start":"03:10.265 ","End":"03:14.120","Text":"If we go with that one and we skip e,"},{"Start":"03:14.120 ","End":"03:16.505","Text":"it means we\u0027ve eliminated b as well,"},{"Start":"03:16.505 ","End":"03:22.490","Text":"we\u0027ve eliminated c. We think d can be correct because if we remove hydroxide ions,"},{"Start":"03:22.490 ","End":"03:27.980","Text":"it means we\u0027re removing basic molecules out of this."},{"Start":"03:27.980 ","End":"03:36.060","Text":"In theory, our pH will be lowered therefore d would be our correct answer."}],"ID":29376},{"Watched":false,"Name":"Biological Buffers","Duration":"9m 40s","ChapterTopicVideoID":27681,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.625","Text":"Hi there. We\u0027re within the chapter on water,"},{"Start":"00:02.625 ","End":"00:05.370","Text":"covering topic of ionization of water."},{"Start":"00:05.370 ","End":"00:09.464","Text":"We will be talking further about biological buffers."},{"Start":"00:09.464 ","End":"00:10.680","Text":"By the end of this section,"},{"Start":"00:10.680 ","End":"00:12.960","Text":"you will be able to understand biological buffers,"},{"Start":"00:12.960 ","End":"00:14.940","Text":"name important biological buffer systems,"},{"Start":"00:14.940 ","End":"00:17.295","Text":"and know the importance of pH regulation."},{"Start":"00:17.295 ","End":"00:18.810","Text":"Biological buffers."},{"Start":"00:18.810 ","End":"00:20.880","Text":"The intracellular and extracellular fluids of"},{"Start":"00:20.880 ","End":"00:26.955","Text":"multicellular organisms have a characteristic and nearly constant pH."},{"Start":"00:26.955 ","End":"00:30.420","Text":"The organisms\u0027 first line of defense against"},{"Start":"00:30.420 ","End":"00:34.680","Text":"changes in internal pH is provided by buffer systems."},{"Start":"00:34.680 ","End":"00:40.315","Text":"The cytoplasm of most cells contain high concentration of proteins,"},{"Start":"00:40.315 ","End":"00:46.955","Text":"which contain many amino acids with functional groups that are weak acids or weak bases."},{"Start":"00:46.955 ","End":"00:50.834","Text":"For example, the side chain of histidine has a pKa of 6."},{"Start":"00:50.834 ","End":"00:53.120","Text":"Proteins containing histidine residues,"},{"Start":"00:53.120 ","End":"00:56.525","Text":"therefore, buffer effectively near neutral pH."},{"Start":"00:56.525 ","End":"00:58.685","Text":"Nucleotides such as ATP,"},{"Start":"00:58.685 ","End":"01:01.205","Text":"as well as many low molecular weight metabolites,"},{"Start":"01:01.205 ","End":"01:06.365","Text":"contain ionizable groups that can contribute buffering power to the cytoplasm."},{"Start":"01:06.365 ","End":"01:10.340","Text":"Some highly specialized organelles and extracellular compartments"},{"Start":"01:10.340 ","End":"01:13.955","Text":"have high concentrations of compounds that contribute buffering capacity."},{"Start":"01:13.955 ","End":"01:16.850","Text":"Organic acids buffer the vacuoles of plant cells."},{"Start":"01:16.850 ","End":"01:18.670","Text":"Ammonia buffers urine."},{"Start":"01:18.670 ","End":"01:23.420","Text":"What you see here is the amino acid histidine as mentioned,"},{"Start":"01:23.420 ","End":"01:27.515","Text":"and it is a component of proteins."},{"Start":"01:27.515 ","End":"01:32.000","Text":"Proteins are made up of amino acids."},{"Start":"01:32.000 ","End":"01:35.060","Text":"Remember, we said the short for amino acid, Xa,"},{"Start":"01:35.060 ","End":"01:39.395","Text":"1 amino acid, histidine,"},{"Start":"01:39.395 ","End":"01:41.390","Text":"is a weak acid."},{"Start":"01:41.390 ","End":"01:44.840","Text":"It is a proton donor."},{"Start":"01:44.840 ","End":"01:48.125","Text":"Here\u0027s the proton, here\u0027s our hydrogen,"},{"Start":"01:48.125 ","End":"01:52.145","Text":"and it can actually dissociate from it."},{"Start":"01:52.145 ","End":"01:54.515","Text":"You see this reversible reaction here,"},{"Start":"01:54.515 ","End":"01:59.030","Text":"where you have the histidine after it\u0027s detached,"},{"Start":"01:59.030 ","End":"02:01.100","Text":"dissociated from the proton,"},{"Start":"02:01.100 ","End":"02:02.330","Text":"from the hydrogen ion,"},{"Start":"02:02.330 ","End":"02:03.664","Text":"and in essence,"},{"Start":"02:03.664 ","End":"02:06.470","Text":"acts as an acid."},{"Start":"02:06.470 ","End":"02:14.325","Text":"The pKa of the protonated nitrogen of the side chain is 6."},{"Start":"02:14.325 ","End":"02:19.940","Text":"This nitrogen side chain can donate the hydrogen,"},{"Start":"02:19.940 ","End":"02:25.535","Text":"and this reversible reaction has the pKa of 6."},{"Start":"02:25.535 ","End":"02:31.915","Text":"It allows proteins that contain histidine to act as buffers."},{"Start":"02:31.915 ","End":"02:34.730","Text":"This is an example of a biological buffer,"},{"Start":"02:34.730 ","End":"02:41.255","Text":"2 especially important buffers are the phosphate and bicarbonate systems."},{"Start":"02:41.255 ","End":"02:43.250","Text":"The phosphate buffer system,"},{"Start":"02:43.250 ","End":"02:46.910","Text":"which acts in the cytoplasm of all cells,"},{"Start":"02:46.910 ","End":"02:50.690","Text":"consists of H_2PO_4 minus as"},{"Start":"02:50.690 ","End":"02:57.315","Text":"the proton donor and H_2PO_4^2 minus as the proton acceptor."},{"Start":"02:57.315 ","End":"03:02.120","Text":"What you see here, the reversible reaction is between the proton donor,"},{"Start":"03:02.120 ","End":"03:06.560","Text":"see it\u0027s donated the proton and the proton acceptor."},{"Start":"03:06.560 ","End":"03:14.220","Text":"The phosphate buffer system is maximally effective at a pH close to its pKa of 6.86,"},{"Start":"03:14.220 ","End":"03:20.390","Text":"and thus, it tends to resist pH changes in the range between about 5.9 and 7.9."},{"Start":"03:20.390 ","End":"03:25.580","Text":"If you remember before we talked about that plateau,"},{"Start":"03:25.580 ","End":"03:27.245","Text":"it is the buffering region."},{"Start":"03:27.245 ","End":"03:29.720","Text":"If it\u0027s 6.86,"},{"Start":"03:29.720 ","End":"03:31.625","Text":"1 above and 1 below,"},{"Start":"03:31.625 ","End":"03:38.090","Text":"it would be 7.86 and 1 below 5.86."},{"Start":"03:38.090 ","End":"03:47.730","Text":"Surrounding these out, it would be 5.9 and 7.9,"},{"Start":"03:47.730 ","End":"03:50.345","Text":"as you see right here."},{"Start":"03:50.345 ","End":"03:53.450","Text":"It is therefore an effective buffer in biological fluids."},{"Start":"03:53.450 ","End":"03:54.620","Text":"In mammals, for example,"},{"Start":"03:54.620 ","End":"04:03.100","Text":"extracellular fluids and most cytoplasmic compartments have a pH in the range of 6.9-7.4."},{"Start":"04:03.100 ","End":"04:05.480","Text":"In order to buffer these pHs,"},{"Start":"04:05.480 ","End":"04:08.240","Text":"you want a buffer region that includes this."},{"Start":"04:08.240 ","End":"04:12.920","Text":"Therefore, the phosphate buffer system is a good buffer system"},{"Start":"04:12.920 ","End":"04:17.660","Text":"for organisms and their cellular environment and extracellular fluids."},{"Start":"04:17.660 ","End":"04:23.000","Text":"While I mentioned, this is used for the cytoplasm and the extracellular fluid."},{"Start":"04:23.000 ","End":"04:25.685","Text":"We also have the blood plasma,"},{"Start":"04:25.685 ","End":"04:27.260","Text":"which is buffered, in part,"},{"Start":"04:27.260 ","End":"04:29.735","Text":"by the bicarbonate system, which we see here."},{"Start":"04:29.735 ","End":"04:32.180","Text":"This buffer system is complex because 1 of its components,"},{"Start":"04:32.180 ","End":"04:34.595","Text":"carbonic acid, H_2CO_3,"},{"Start":"04:34.595 ","End":"04:37.170","Text":"is formed from dissolved carbon dioxide in water."},{"Start":"04:37.170 ","End":"04:39.335","Text":"This is how we signify that it\u0027s dissolved,"},{"Start":"04:39.335 ","End":"04:41.390","Text":"and it happens in a reversible reaction."},{"Start":"04:41.390 ","End":"04:43.700","Text":"You have CO_2 that\u0027s dissolved with water,"},{"Start":"04:43.700 ","End":"04:48.225","Text":"and it\u0027s interchangeable with H_2CO_3, the carbonic acid."},{"Start":"04:48.225 ","End":"04:51.080","Text":"The reaction formula for this,"},{"Start":"04:51.080 ","End":"04:53.450","Text":"and this we\u0027ll call K_2 is H_2CO_3,"},{"Start":"04:53.450 ","End":"04:56.150","Text":"the carbonic acid over the reactants,"},{"Start":"04:56.150 ","End":"04:58.435","Text":"which is CO_2 dissolved in H_2O."},{"Start":"04:58.435 ","End":"05:00.845","Text":"Now, making this even more complex,"},{"Start":"05:00.845 ","End":"05:04.520","Text":"carbon dioxide is a gas under normal conditions and the concentration of"},{"Start":"05:04.520 ","End":"05:08.705","Text":"dissolved CO_2 is the result of equilibration with CO_2 of a gas phase."},{"Start":"05:08.705 ","End":"05:13.790","Text":"You have CO_2 gas irreversible with dissolved CO_2 with water,"},{"Start":"05:13.790 ","End":"05:16.040","Text":"so then, you have this other formula."},{"Start":"05:16.040 ","End":"05:20.420","Text":"This makes this buffer systems complex because it actually is dependent"},{"Start":"05:20.420 ","End":"05:25.445","Text":"on all equilibrium of these reactions."},{"Start":"05:25.445 ","End":"05:31.340","Text":"The pH of a bicarbonate buffer system depends on the concentration of H_2CO_3,"},{"Start":"05:31.340 ","End":"05:35.685","Text":"carbonic acid, and HCO_3 minus,"},{"Start":"05:35.685 ","End":"05:38.645","Text":"the proton donor and acceptor components."},{"Start":"05:38.645 ","End":"05:42.335","Text":"The concentration of H_2CO_3 of the carbonic acid,"},{"Start":"05:42.335 ","End":"05:45.530","Text":"in turn, depends on the concentration of dissolved CO_2,"},{"Start":"05:45.530 ","End":"05:48.725","Text":"which in turn depends on the concentration of CO_2"},{"Start":"05:48.725 ","End":"05:52.520","Text":"in the gas phase called the partial pressure of CO_2."},{"Start":"05:52.520 ","End":"05:55.370","Text":"Thus, the pH of the bicarbonate buffer exposed"},{"Start":"05:55.370 ","End":"05:58.249","Text":"to a gas phase is ultimately determined by the concentration"},{"Start":"05:58.249 ","End":"06:04.115","Text":"of HCO_3 minus in the aqueous phase and the partial pressure of CO2 in the gas phase."},{"Start":"06:04.115 ","End":"06:05.360","Text":"Bottom line to say,"},{"Start":"06:05.360 ","End":"06:07.490","Text":"we have 2 main,"},{"Start":"06:07.490 ","End":"06:09.830","Text":"2 important biological buffer systems,"},{"Start":"06:09.830 ","End":"06:11.954","Text":"1 is the phosphate and 1 bicarbonate,"},{"Start":"06:11.954 ","End":"06:17.390","Text":"with the bicarbonate being a much more complex system than the others."},{"Start":"06:17.390 ","End":"06:19.685","Text":"Biological implications."},{"Start":"06:19.685 ","End":"06:21.635","Text":"What does this actually all mean?"},{"Start":"06:21.635 ","End":"06:25.865","Text":"Human blood plasma has a pH close to 7.4 normally."},{"Start":"06:25.865 ","End":"06:29.825","Text":"Should the pH regulating mechanisms fail,"},{"Start":"06:29.825 ","End":"06:34.835","Text":"the pH of the blood can fall to even 6.8 or below,"},{"Start":"06:34.835 ","End":"06:37.205","Text":"leading to irreparable cell damage and death."},{"Start":"06:37.205 ","End":"06:38.690","Text":"We said in other diseases,"},{"Start":"06:38.690 ","End":"06:41.465","Text":"the pH may rise to lethal levels."},{"Start":"06:41.465 ","End":"06:43.475","Text":"Meaning, it\u0027s not just 1 way."},{"Start":"06:43.475 ","End":"06:46.175","Text":"It can fall or rise in either way."},{"Start":"06:46.175 ","End":"06:50.180","Text":"Although many aspects of cell structure and function are influenced by pH,"},{"Start":"06:50.180 ","End":"06:55.285","Text":"it is the catalytic activity of enzymes that is especially sensitive."},{"Start":"06:55.285 ","End":"07:02.495","Text":"Enzymes typically show maximum catalytic activity at a characteristic pH,"},{"Start":"07:02.495 ","End":"07:05.420","Text":"and it\u0027s called the pH optimum."},{"Start":"07:05.420 ","End":"07:07.610","Text":"As you can see in the figure here,"},{"Start":"07:07.610 ","End":"07:11.660","Text":"you have this range where these enzymes,"},{"Start":"07:11.660 ","End":"07:14.690","Text":"this pepsin, this is trypsin alkaline phosphatase,"},{"Start":"07:14.690 ","End":"07:18.570","Text":"where it has maximum activity at different pH."},{"Start":"07:18.570 ","End":"07:21.920","Text":"Pepsin, it\u0027s at an acidic pH,"},{"Start":"07:21.920 ","End":"07:24.710","Text":"which makes sense to where it sits in our body."},{"Start":"07:24.710 ","End":"07:26.225","Text":"We have it in our gut."},{"Start":"07:26.225 ","End":"07:29.855","Text":"You have trypsin that it\u0027s a higher pH above 6."},{"Start":"07:29.855 ","End":"07:31.888","Text":"You have alkaline phosphatase."},{"Start":"07:31.888 ","End":"07:33.770","Text":"Alkaline, that means,"},{"Start":"07:33.770 ","End":"07:35.315","Text":"in a way, basic."},{"Start":"07:35.315 ","End":"07:38.280","Text":"That\u0027s at a higher basic pH."},{"Start":"07:38.280 ","End":"07:42.455","Text":"Basically, the catalytic activity of enzymes"},{"Start":"07:42.455 ","End":"07:46.295","Text":"will often decline sharply on either side of the optimum pH."},{"Start":"07:46.295 ","End":"07:48.440","Text":"You see it\u0027s very steep."},{"Start":"07:48.440 ","End":"07:52.280","Text":"It\u0027s very efficient at the optimum pH,"},{"Start":"07:52.280 ","End":"07:54.050","Text":"and then aside from it,"},{"Start":"07:54.050 ","End":"07:56.569","Text":"it drops very rapidly."},{"Start":"07:56.569 ","End":"07:58.820","Text":"Thus, a small change in pH can make"},{"Start":"07:58.820 ","End":"08:02.900","Text":"the large difference in the rate of some crucial enzyme-catalyzed reactions."},{"Start":"08:02.900 ","End":"08:04.475","Text":"Going back to this figure,"},{"Start":"08:04.475 ","End":"08:10.670","Text":"I briefly mentioned pepsin is a digestive enzyme secreted into gastric juice,"},{"Start":"08:10.670 ","End":"08:12.770","Text":"so it makes sense."},{"Start":"08:12.770 ","End":"08:15.185","Text":"The acidic environment, therefore,"},{"Start":"08:15.185 ","End":"08:20.990","Text":"needs to have the ability to function at this low pH at the acidic environment."},{"Start":"08:20.990 ","End":"08:25.670","Text":"Trypsin, a digestive enzyme that acts in the small intestine,"},{"Start":"08:25.670 ","End":"08:27.470","Text":"has a different pH."},{"Start":"08:27.470 ","End":"08:29.990","Text":"Small intestine has a different environment of pH,"},{"Start":"08:29.990 ","End":"08:32.810","Text":"and the alkaline phosphatase of bone tissue is"},{"Start":"08:32.810 ","End":"08:36.665","Text":"a hydrolytic enzyme thought to aid in bone mineralization."},{"Start":"08:36.665 ","End":"08:42.765","Text":"Then in the bones, we tend to have more of that pH that\u0027s closer to 7."},{"Start":"08:42.765 ","End":"08:45.875","Text":"But still, more an alkaline environment,"},{"Start":"08:45.875 ","End":"08:50.225","Text":"more basic environment than you would find in the digestive tract."},{"Start":"08:50.225 ","End":"08:53.450","Text":"All this has to do with the biological implications."},{"Start":"08:53.450 ","End":"08:57.890","Text":"Biological control of pH of cells and body fluids is therefore"},{"Start":"08:57.890 ","End":"09:03.205","Text":"central in its importance in metabolism and cellular activities."},{"Start":"09:03.205 ","End":"09:05.030","Text":"If we summarize this,"},{"Start":"09:05.030 ","End":"09:06.230","Text":"in cells and tissues,"},{"Start":"09:06.230 ","End":"09:08.600","Text":"phosphate and bicarbonate buffer systems maintain"},{"Start":"09:08.600 ","End":"09:13.835","Text":"intracellular and extracellular fluids at their optimum physiological pH,"},{"Start":"09:13.835 ","End":"09:16.160","Text":"which is usually close to pH 7."},{"Start":"09:16.160 ","End":"09:19.400","Text":"Enzymes generally work optimally at this pH,"},{"Start":"09:19.400 ","End":"09:23.780","Text":"the pH of the environment where they are adapted to"},{"Start":"09:23.780 ","End":"09:28.670","Text":"and maintain good rate of function and reactions within these environments."},{"Start":"09:28.670 ","End":"09:33.800","Text":"At this point, you should understand the concept of biological buffers,"},{"Start":"09:33.800 ","End":"09:35.960","Text":"name important biological buffer systems."},{"Start":"09:35.960 ","End":"09:37.670","Text":"We specifically talked about 2,"},{"Start":"09:37.670 ","End":"09:40.950","Text":"and know the importance of pH regulation."}],"ID":29377},{"Watched":false,"Name":"Exercise 26","Duration":"1m 33s","ChapterTopicVideoID":28148,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:07.154","Text":"Hi there, welcome to a section of biological buffers and we will start with an exercise."},{"Start":"00:07.154 ","End":"00:11.475","Text":"How do proteins in the cytoplasm contribute to cellular pH?"},{"Start":"00:11.475 ","End":"00:13.350","Text":"The intracellular and extracellular fluids of"},{"Start":"00:13.350 ","End":"00:16.800","Text":"multi-cellular organisms have a characteristic nearly constant pH,"},{"Start":"00:16.800 ","End":"00:19.215","Text":"which is crucial for proper functioning."},{"Start":"00:19.215 ","End":"00:22.380","Text":"The organisms\u0027 first line of defense against changes in"},{"Start":"00:22.380 ","End":"00:25.740","Text":"internal pH is provided by buffer systems."},{"Start":"00:25.740 ","End":"00:30.885","Text":"The cytoplasm of most cells contains high concentrations of proteins,"},{"Start":"00:30.885 ","End":"00:36.740","Text":"which contain many amino acids with functional groups that are weak acids or weak bases."},{"Start":"00:36.740 ","End":"00:41.480","Text":"These contribute buffering capacity to the cytoplasm or to the cell."},{"Start":"00:41.480 ","End":"00:46.265","Text":"For example, we talked about the side chain of histidine,"},{"Start":"00:46.265 ","End":"00:49.120","Text":"which has a pKa of 6."},{"Start":"00:49.120 ","End":"00:52.220","Text":"Proteins containing histidine residues therefore buffer"},{"Start":"00:52.220 ","End":"00:56.315","Text":"effectively near-neutral pH around 6."},{"Start":"00:56.315 ","End":"00:58.160","Text":"So if it has a pKa of 6,"},{"Start":"00:58.160 ","End":"01:01.760","Text":"it means its buffering region is between 5 and 7."},{"Start":"01:01.760 ","End":"01:06.604","Text":"Therefore, it buffers effectively near the neutral pH."},{"Start":"01:06.604 ","End":"01:11.810","Text":"Nucleotides such as ATP as well as many low molecular weight metabolites contain"},{"Start":"01:11.810 ","End":"01:17.165","Text":"ionizable groups that can contribute buffering power to the cytoplasm."},{"Start":"01:17.165 ","End":"01:19.610","Text":"Some highly specialized organelles and"},{"Start":"01:19.610 ","End":"01:22.820","Text":"extracellular compartments have high concentrations of compounds that"},{"Start":"01:22.820 ","End":"01:25.610","Text":"contribute buffering capacity as well as"},{"Start":"01:25.610 ","End":"01:28.820","Text":"organic acids that buffer the vacuoles of plants cells,"},{"Start":"01:28.820 ","End":"01:32.040","Text":"ammonia buffers in urine, etc."}],"ID":29378},{"Watched":false,"Name":"Exercise 27","Duration":"3m 12s","ChapterTopicVideoID":27656,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.260 ","End":"00:05.220","Text":"Hey there, we are within an exercise covering biological buffers."},{"Start":"00:05.220 ","End":"00:09.145","Text":"2 important biological buffers were mentioned in the lesson,"},{"Start":"00:09.145 ","End":"00:11.350","Text":"name and explain 1 of these."},{"Start":"00:11.350 ","End":"00:15.610","Text":"The 2 important biological buffers are the phosphate and bicarbonate systems."},{"Start":"00:15.610 ","End":"00:18.790","Text":"Let\u0027s start with the phosphate buffer system,"},{"Start":"00:18.790 ","End":"00:23.320","Text":"which acts in the cytoplasm of all cells and consists of H_2PO_4 minus"},{"Start":"00:23.320 ","End":"00:28.255","Text":"as a proton donor and H_2PO_4^2- as proton acceptor."},{"Start":"00:28.255 ","End":"00:30.639","Text":"It\u0027s a reversible reaction between"},{"Start":"00:30.639 ","End":"00:33.370","Text":"the proton donor and the proton acceptors as seen here,"},{"Start":"00:33.370 ","End":"00:37.660","Text":"H_2PO_4- is donating the proton"},{"Start":"00:37.660 ","End":"00:42.485","Text":"you have here and you have H_2PO_4^2- as the proton acceptor."},{"Start":"00:42.485 ","End":"00:44.930","Text":"The phosphate buffer system is maximally effective"},{"Start":"00:44.930 ","End":"00:48.830","Text":"at a pH close to its pKa, which is 6.86."},{"Start":"00:48.830 ","End":"00:55.930","Text":"Thus it tends to resist pH changes in the range between 5.9 and 7.9."},{"Start":"00:55.930 ","End":"01:03.390","Text":"Remember we talked about the buffering region being about 1 pH below and above."},{"Start":"01:03.390 ","End":"01:08.565","Text":"If you have 5.86 and 7.86 rounding it up,"},{"Start":"01:08.565 ","End":"01:15.890","Text":"it\u0027s like 7.9 and 5.9 and that is the buffering region,"},{"Start":"01:15.890 ","End":"01:20.555","Text":"rendering it able to resist pH changes in this range."},{"Start":"01:20.555 ","End":"01:26.630","Text":"It is therefore an effective buffer in biological fluids and in mammals, for example,"},{"Start":"01:26.630 ","End":"01:30.140","Text":"extracellular fluids and most cytoplasmic compartments have a pH"},{"Start":"01:30.140 ","End":"01:33.760","Text":"in the range of 6.9 through 7.4,"},{"Start":"01:33.760 ","End":"01:37.400","Text":"which means it falls within this range."},{"Start":"01:37.400 ","End":"01:46.145","Text":"If you have this and you have the upper and lower limit being 5.9 and 7.9,"},{"Start":"01:46.145 ","End":"01:50.250","Text":"these fall within this buffering region."},{"Start":"01:50.250 ","End":"01:54.560","Text":"The second buffer system we mentioned is the bicarbonate system."},{"Start":"01:54.560 ","End":"01:58.820","Text":"This one is consisting of carbonic acid H_2CO_3 as"},{"Start":"01:58.820 ","End":"02:03.650","Text":"proton donor and bicarbonate HCO3 minus as the proton acceptor."},{"Start":"02:03.650 ","End":"02:05.750","Text":"You see the reversible reaction here,"},{"Start":"02:05.750 ","End":"02:07.025","Text":"the K for the reaction."},{"Start":"02:07.025 ","End":"02:11.180","Text":"The bicarbonate system is involved in the buffering of"},{"Start":"02:11.180 ","End":"02:16.055","Text":"blood plasma since blood plasma is buffered in part by the system."},{"Start":"02:16.055 ","End":"02:18.650","Text":"This buffer system is more complex than"},{"Start":"02:18.650 ","End":"02:22.280","Text":"other conjugate acid-base pairs because 1 of its components,"},{"Start":"02:22.280 ","End":"02:24.965","Text":"carbonic acid H_2CO_3,"},{"Start":"02:24.965 ","End":"02:28.910","Text":"is formed from dissolved carbon dioxide,"},{"Start":"02:28.910 ","End":"02:32.250","Text":"CO_2 designated by small d and water."},{"Start":"02:32.250 ","End":"02:35.885","Text":"In a reversible reaction that is as seen here,"},{"Start":"02:35.885 ","End":"02:40.490","Text":"CO_2 dissolved with water forms H_2CO_3,"},{"Start":"02:40.490 ","End":"02:43.055","Text":"and this is a reversible reaction."},{"Start":"02:43.055 ","End":"02:46.520","Text":"CO_2 is normally found in gas form and it"},{"Start":"02:46.520 ","End":"02:52.925","Text":"also then interchanges to the dissolved form in water."},{"Start":"02:52.925 ","End":"02:58.955","Text":"There is actually another reaction that plays a role in this system."},{"Start":"02:58.955 ","End":"03:03.874","Text":"If you mentioned either 1 of these biological buffer systems,"},{"Start":"03:03.874 ","End":"03:11.939","Text":"either phosphate buffer system or the bicarbonate system, you are golden."}],"ID":29379},{"Watched":false,"Name":"Exercise 28","Duration":"1m 18s","ChapterTopicVideoID":27657,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.670","Text":"Hi there, welcome back to biological buffers, with another exercise."},{"Start":"00:05.670 ","End":"00:09.090","Text":"Biological control of the pH of cells and"},{"Start":"00:09.090 ","End":"00:12.315","Text":"body fluids is of central importance for proper functioning."},{"Start":"00:12.315 ","End":"00:17.099","Text":"What are biological implications of a change in pH of human blood plasma?"},{"Start":"00:17.099 ","End":"00:20.640","Text":"We\u0027ve talked about this in 2 directions."},{"Start":"00:20.640 ","End":"00:24.705","Text":"Human and blood plasma normally has a pH close to 7.4."},{"Start":"00:24.705 ","End":"00:28.920","Text":"If the pH regulating mechanisms fail or become overwhelmed,"},{"Start":"00:28.920 ","End":"00:31.710","Text":"as may happen in severe uncontrolled diabetes,"},{"Start":"00:31.710 ","End":"00:37.185","Text":"for example, when an overproduction of metabolic acids cause acidosis,"},{"Start":"00:37.185 ","End":"00:40.440","Text":"meaning the pH decreases."},{"Start":"00:40.440 ","End":"00:43.060","Text":"Acidosis, right?"},{"Start":"00:43.060 ","End":"00:47.030","Text":"Acid, meaning it is of lower pH,"},{"Start":"00:47.030 ","End":"00:52.835","Text":"acidic pH, pH of the blood can fall to 6.8 or below,"},{"Start":"00:52.835 ","End":"00:55.790","Text":"leading to irreparable cell damage and death."},{"Start":"00:55.790 ","End":"01:01.535","Text":"In other diseases, the pH may rise to lethal levels by becoming more basic."},{"Start":"01:01.535 ","End":"01:08.210","Text":"So either way, pH needs to be kept at close proximity to 7.4 because"},{"Start":"01:08.210 ","End":"01:11.690","Text":"either a dropped basic levels or a rise to"},{"Start":"01:11.690 ","End":"01:17.670","Text":"acidic levels can cause grave damage to functioning."}],"ID":29380},{"Watched":false,"Name":"Exercise 29","Duration":"1m 43s","ChapterTopicVideoID":27658,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.765","Text":"Welcome to another exercise within Biological Buffers."},{"Start":"00:03.765 ","End":"00:06.120","Text":"What is especially sensitive with regard to"},{"Start":"00:06.120 ","End":"00:09.720","Text":"proper cell functions and what is the pH optimum?"},{"Start":"00:09.720 ","End":"00:15.014","Text":"Although many aspects of cell structure and function are influenced by pH,"},{"Start":"00:15.014 ","End":"00:20.145","Text":"it is the catalytic activity of enzymes that is especially sensitive."},{"Start":"00:20.145 ","End":"00:25.140","Text":"Enzymes typically show maximum catalytic activity at a characteristic pH,"},{"Start":"00:25.140 ","End":"00:27.090","Text":"called the pH optimum."},{"Start":"00:27.090 ","End":"00:31.520","Text":"Their catalytic activity often declines sharply on either side of the optimum pH."},{"Start":"00:31.520 ","End":"00:33.435","Text":"As can be seen here in the figure,"},{"Start":"00:33.435 ","End":"00:35.130","Text":"you have the percent maximum activity."},{"Start":"00:35.130 ","End":"00:36.900","Text":"This is the percent maximum activity,"},{"Start":"00:36.900 ","End":"00:38.105","Text":"almost 100 percent,"},{"Start":"00:38.105 ","End":"00:41.445","Text":"and it is at a specific pH."},{"Start":"00:41.445 ","End":"00:43.625","Text":"Thus a small change in pH can make"},{"Start":"00:43.625 ","End":"00:47.165","Text":"a large difference in the rate of some crucial enzyme-catalyzed reactions."},{"Start":"00:47.165 ","End":"00:49.565","Text":"So if you\u0027re looking at any one of these,"},{"Start":"00:49.565 ","End":"00:53.150","Text":"let\u0027s say this is for alkaline phosphatase."},{"Start":"00:53.150 ","End":"00:54.635","Text":"It\u0027s around 9,"},{"Start":"00:54.635 ","End":"00:56.675","Text":"pH of around 9."},{"Start":"00:56.675 ","End":"00:58.315","Text":"I don\u0027t know 2,"},{"Start":"00:58.315 ","End":"01:01.380","Text":"and our gut, it\u0027s around pH of 2."},{"Start":"01:01.380 ","End":"01:04.655","Text":"We have trypsin and that\u0027s around 7."},{"Start":"01:04.655 ","End":"01:06.710","Text":"When you see pepsin,"},{"Start":"01:06.710 ","End":"01:08.825","Text":"when it goes up to pH 3,"},{"Start":"01:08.825 ","End":"01:13.865","Text":"its activity drops by 50 percent with one pH change."},{"Start":"01:13.865 ","End":"01:17.930","Text":"If you have alkaline phosphatase at 9,"},{"Start":"01:17.930 ","End":"01:20.420","Text":"if we look at trypsin or it\u0027s around 7,"},{"Start":"01:20.420 ","End":"01:22.460","Text":"if we drop it to 5,"},{"Start":"01:22.460 ","End":"01:26.165","Text":"it is below 50 percent activity."},{"Start":"01:26.165 ","End":"01:30.530","Text":"This signifies the importance of that pH range"},{"Start":"01:30.530 ","End":"01:35.465","Text":"for enzymatic activity to be optimal and efficient."},{"Start":"01:35.465 ","End":"01:38.555","Text":"The pH optimum differs between enzymes,"},{"Start":"01:38.555 ","End":"01:42.550","Text":"as was seen and signified here."}],"ID":29381},{"Watched":false,"Name":"Exercise 30","Duration":"48s","ChapterTopicVideoID":27659,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.025","Text":"Hey, there. We\u0027re within biological buffers and we are testing our knowledge."},{"Start":"00:05.025 ","End":"00:09.045","Text":"How do buffers prevent pH changes?"},{"Start":"00:09.045 ","End":"00:11.069","Text":"Well, by this time,"},{"Start":"00:11.069 ","End":"00:13.125","Text":"this should be an easy answer for you guys."},{"Start":"00:13.125 ","End":"00:15.440","Text":"Buffers absorb the free hydrogen ions and"},{"Start":"00:15.440 ","End":"00:18.605","Text":"hydroxide ions that result from chemical reactions."},{"Start":"00:18.605 ","End":"00:20.390","Text":"Because they can bond to these ions,"},{"Start":"00:20.390 ","End":"00:24.035","Text":"they prevent increases or decreases in pH."},{"Start":"00:24.035 ","End":"00:27.905","Text":"An example of a buffer system is the bicarbonate system in the human body."},{"Start":"00:27.905 ","End":"00:31.040","Text":"This system is able to absorb hydrogen and hydroxide ions,"},{"Start":"00:31.040 ","End":"00:35.120","Text":"preventing changes in pH and enabling cells to function properly."},{"Start":"00:35.120 ","End":"00:39.139","Text":"Of course, this is within the range of the buffering region"},{"Start":"00:39.139 ","End":"00:43.280","Text":"that is relevant for each buffer system,"},{"Start":"00:43.280 ","End":"00:48.690","Text":"and if you remember, that changes from buffer system to buffer system."}],"ID":29382},{"Watched":false,"Name":"Water as a Reactant","Duration":"7m 16s","ChapterTopicVideoID":27680,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.480","Text":"Hi there. We\u0027re within Ionization of Water in the chapter of Water,"},{"Start":"00:03.480 ","End":"00:06.345","Text":"and we will be talking about water as a reactant."},{"Start":"00:06.345 ","End":"00:08.910","Text":"By the end of this section, we\u0027ll be able to understand water as"},{"Start":"00:08.910 ","End":"00:12.465","Text":"a reactant and define hydrolysis and condensation reactions."},{"Start":"00:12.465 ","End":"00:18.321","Text":"Water is not just the solvent in which the chemical reactions of living cells occur."},{"Start":"00:18.321 ","End":"00:25.085","Text":"It is very often a direct participant in such cellular reactions."},{"Start":"00:25.085 ","End":"00:28.970","Text":"The formation of ATP from ADP and inorganic phosphate is"},{"Start":"00:28.970 ","End":"00:33.860","Text":"a condensation reaction in which the elements of water are eliminated."},{"Start":"00:33.860 ","End":"00:37.010","Text":"It condensates. In other word,"},{"Start":"00:37.010 ","End":"00:43.040","Text":"it is a reaction in which 2 molecules join into a larger one and eject a water molecule."},{"Start":"00:43.040 ","End":"00:45.185","Text":"When we think of condensation,"},{"Start":"00:45.185 ","End":"00:48.110","Text":"we think of water being released, or eliminated,"},{"Start":"00:48.110 ","End":"00:51.245","Text":"or reduced in the specific system that we\u0027re talking,"},{"Start":"00:51.245 ","End":"00:53.315","Text":"that is, condensate it."},{"Start":"00:53.315 ","End":"00:57.860","Text":"The reverse of this reaction is a hydrolysis reaction."},{"Start":"00:57.860 ","End":"01:00.530","Text":"It\u0027s basically cleavage,"},{"Start":"01:00.530 ","End":"01:03.830","Text":"accompanied by the addition of the element of water."},{"Start":"01:03.830 ","End":"01:08.000","Text":"Biological hydrolysis can also be explained as the cleavage of biomolecules where"},{"Start":"01:08.000 ","End":"01:10.580","Text":"water molecule is consumed to effect"},{"Start":"01:10.580 ","End":"01:13.760","Text":"the separation of a larger molecule into component parts."},{"Start":"01:13.760 ","End":"01:16.730","Text":"This also comes from Greek,"},{"Start":"01:16.730 ","End":"01:18.680","Text":"as many of the other terms we covered in"},{"Start":"01:18.680 ","End":"01:22.430","Text":"this course and generally in biology and chemistry."},{"Start":"01:22.430 ","End":"01:26.160","Text":"\"Hydro\" in Greek means water,"},{"Start":"01:26.160 ","End":"01:29.435","Text":"and \"lysis\", to unbind."},{"Start":"01:29.435 ","End":"01:34.710","Text":"So you have hydrolysis, water and unbinding."},{"Start":"01:34.710 ","End":"01:38.898","Text":"You\u0027re taking water, you\u0027re introducing it into a molecule,"},{"Start":"01:38.898 ","End":"01:42.424","Text":"you\u0027re causing it to unbind,"},{"Start":"01:42.424 ","End":"01:47.030","Text":"and now you will have 2 molecules because water was added."},{"Start":"01:47.030 ","End":"01:50.300","Text":"So if you see here, you have this,"},{"Start":"01:50.300 ","End":"01:54.560","Text":"what we would call the main molecule of ATP,"},{"Start":"01:54.560 ","End":"01:58.595","Text":"and you have water being added to it."},{"Start":"01:58.595 ","End":"02:02.105","Text":"The water was taken up by this molecule,"},{"Start":"02:02.105 ","End":"02:06.019","Text":"and it allowed to break it up so that,"},{"Start":"02:06.019 ","End":"02:15.830","Text":"right here, water came and added to this oxygen right here and became this phosphate."},{"Start":"02:15.830 ","End":"02:19.190","Text":"You have the OH here, and basically,"},{"Start":"02:19.190 ","End":"02:25.205","Text":"you have the triphosphate had now turned into a diphosphate,"},{"Start":"02:25.205 ","End":"02:29.090","Text":"ATP to ADP, and reverse."},{"Start":"02:29.090 ","End":"02:31.310","Text":"These can come together,"},{"Start":"02:31.310 ","End":"02:33.335","Text":"the hydrogen from here,"},{"Start":"02:33.335 ","End":"02:34.880","Text":"the OH from here,"},{"Start":"02:34.880 ","End":"02:37.775","Text":"together they combine and make H_2O,"},{"Start":"02:37.775 ","End":"02:41.825","Text":"which is released, and they are now 1 molecule."},{"Start":"02:41.825 ","End":"02:46.880","Text":"Hydrolysis reactions are also responsible for the enzymatic depolymerization,"},{"Start":"02:46.880 ","End":"02:50.960","Text":"which means the process of converting a polymer into a monomer or a mixture of monomers,"},{"Start":"02:50.960 ","End":"02:54.555","Text":"they making a polymer a non-polymer."},{"Start":"02:54.555 ","End":"02:58.970","Text":"It is responsible for the enzymatic depolymerization of proteins,"},{"Start":"02:58.970 ","End":"03:02.544","Text":"carbohydrates, and nucleic acids."},{"Start":"03:02.544 ","End":"03:06.275","Text":"Reiterating these terms, condensation reaction,"},{"Start":"03:06.275 ","End":"03:10.340","Text":"you have ADP plus this phosphate and OH,"},{"Start":"03:10.340 ","End":"03:12.220","Text":"you actually squeeze out,"},{"Start":"03:12.220 ","End":"03:17.345","Text":"you condense, you take out the water and the hydrogen from here,"},{"Start":"03:17.345 ","End":"03:20.750","Text":"and you result with the triphosphate because"},{"Start":"03:20.750 ","End":"03:24.740","Text":"this phosphate combines with the diphosphate."},{"Start":"03:24.740 ","End":"03:27.035","Text":"They become a bigger molecule,"},{"Start":"03:27.035 ","End":"03:32.945","Text":"and the OH from this phosphate and the hydrogen from here combine,"},{"Start":"03:32.945 ","End":"03:35.840","Text":"and you get H_2O."},{"Start":"03:35.840 ","End":"03:38.900","Text":"The opposite of this is the hydrolysis reaction,"},{"Start":"03:38.900 ","End":"03:43.670","Text":"where you actually are adding water into it and taking a molecule, a macromolecule,"},{"Start":"03:43.670 ","End":"03:47.060","Text":"and breaking it up into 2 by introducing water,"},{"Start":"03:47.060 ","End":"03:51.850","Text":"hydrolyzing this molecule so it breaks apart into 2 molecules."},{"Start":"03:51.850 ","End":"03:53.930","Text":"Hydrolysis reaction is catalyzed by enzymes,"},{"Start":"03:53.930 ","End":"03:56.624","Text":"called hydrolases, are exergonic,"},{"Start":"03:56.624 ","End":"03:58.745","Text":"meaning, they release energy."},{"Start":"03:58.745 ","End":"04:01.325","Text":"So we can say enzymatic depolarization,"},{"Start":"04:01.325 ","End":"04:05.075","Text":"catalyzed by the enzyme hydrolase, is exergonic."},{"Start":"04:05.075 ","End":"04:08.412","Text":"Polymerization, on the other hand, is endergonic."},{"Start":"04:08.412 ","End":"04:10.099","Text":"So this releases energy,"},{"Start":"04:10.099 ","End":"04:12.750","Text":"and this requires energy,"},{"Start":"04:12.750 ","End":"04:16.310","Text":"taking the 2 molecules and making them into 1,"},{"Start":"04:16.310 ","End":"04:23.420","Text":"where you\u0027re actually doing condensation and water is being released, that is endergonic."},{"Start":"04:23.420 ","End":"04:26.660","Text":"Cells circumvent the thermodynamic obstacle by"},{"Start":"04:26.660 ","End":"04:31.175","Text":"coupling endergonic condensation reactions to exergonic processes,"},{"Start":"04:31.175 ","End":"04:36.040","Text":"such as breakage of the anhydride bond in ATP."},{"Start":"04:36.040 ","End":"04:43.400","Text":"Water and carbon dioxide are the end products of the oxidation of fuel, such as glucose."},{"Start":"04:43.400 ","End":"04:46.280","Text":"The overall reaction is glucose,"},{"Start":"04:46.280 ","End":"04:49.924","Text":"C_6 H_12 O_6 plus 6 molecules of oxygen,"},{"Start":"04:49.924 ","End":"04:55.145","Text":"resulting in 6 molecules of carbon dioxide and 6 molecules of water."},{"Start":"04:55.145 ","End":"04:59.600","Text":"The metabolic water formed by oxidation of foods and stored"},{"Start":"04:59.600 ","End":"05:04.820","Text":"fats is actually enough to allow some animals in very dry habitats,"},{"Start":"05:04.820 ","End":"05:06.550","Text":"like kangaroos, camels, etc.,"},{"Start":"05:06.550 ","End":"05:11.210","Text":"to survive for extended periods without drinking water."},{"Start":"05:11.210 ","End":"05:17.150","Text":"The CO_2 produced by glucose oxidation is converted in erythrocytes,"},{"Start":"05:17.150 ","End":"05:18.530","Text":"which are red blood cells,"},{"Start":"05:18.530 ","End":"05:24.800","Text":"to the more soluble HCO_3- in a reaction catalyzed by the enzyme, carbonic anhydrase."},{"Start":"05:24.800 ","End":"05:28.080","Text":"That\u0027s what you see here, so you have CO_2 plus H_2O,"},{"Start":"05:28.080 ","End":"05:29.840","Text":"or carbon dioxide plus water."},{"Start":"05:29.840 ","End":"05:32.689","Text":"It\u0027s an irreversible reaction that,"},{"Start":"05:32.689 ","End":"05:35.925","Text":"upon hydrolysis, or adding of water,"},{"Start":"05:35.925 ","End":"05:41.494","Text":"you get HCO_3- plus H. To reiterate, in this reaction,"},{"Start":"05:41.494 ","End":"05:46.160","Text":"water is a substrate as well as a participant in the proton transfer by forming"},{"Start":"05:46.160 ","End":"05:51.280","Text":"a network of hydrogen-bonded water molecules through which proton-hopping occurs."},{"Start":"05:51.280 ","End":"05:55.670","Text":"Green plants and algae use solar energy,"},{"Start":"05:55.670 ","End":"05:57.320","Text":"the energy of sunlight,"},{"Start":"05:57.320 ","End":"06:00.905","Text":"to split water in the process of photosynthesis."},{"Start":"06:00.905 ","End":"06:05.370","Text":"So what you see here is water molecules, 2 of them,"},{"Start":"06:05.370 ","End":"06:12.370","Text":"plus 2A results in oxygen plus 2AH_2."},{"Start":"06:13.250 ","End":"06:18.650","Text":"In this reaction, A is an electron-accepting species."},{"Start":"06:18.650 ","End":"06:23.599","Text":"It just represents nothing which varies with the type of photosynthetic organism."},{"Start":"06:23.599 ","End":"06:27.620","Text":"You have this electron-accepting species, you have the water,"},{"Start":"06:27.620 ","End":"06:35.065","Text":"and it will accept the hydrogen and become 2AH_2."},{"Start":"06:35.065 ","End":"06:39.140","Text":"Water here acts as the electron donor."},{"Start":"06:39.140 ","End":"06:41.060","Text":"In an oxidation-reduction sequence,"},{"Start":"06:41.060 ","End":"06:43.355","Text":"that is fundamental to all life."},{"Start":"06:43.355 ","End":"06:47.480","Text":"The main point to take home from this is that water is both a solvent in which"},{"Start":"06:47.480 ","End":"06:52.969","Text":"metabolic reactions occur and a reactant in many biochemical processes,"},{"Start":"06:52.969 ","End":"06:56.815","Text":"including hydrolysis, condensation, and oxidation-reduction reactions."},{"Start":"06:56.815 ","End":"07:00.500","Text":"To summarize the 2 reaction type mentioned in this lesson,"},{"Start":"07:00.500 ","End":"07:05.990","Text":"hydrolysis adds water to break down a bigger molecule,"},{"Start":"07:05.990 ","End":"07:10.845","Text":"whereas condensation builds up by removing water."},{"Start":"07:10.845 ","End":"07:13.879","Text":"So now you should understand water as a reactant"},{"Start":"07:13.879 ","End":"07:17.940","Text":"and define hydrolysis and condensation reaction."}],"ID":29383},{"Watched":false,"Name":"Exercise 31","Duration":"2m 32s","ChapterTopicVideoID":27644,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.250","Text":"Here we are in an exercise coming from the topic of Water as a Reactant."},{"Start":"00:05.250 ","End":"00:07.110","Text":"Part 1, in this lesson,"},{"Start":"00:07.110 ","End":"00:08.760","Text":"we learned that water is not just the solvent in"},{"Start":"00:08.760 ","End":"00:10.785","Text":"which chemical reactions of living cells occur,"},{"Start":"00:10.785 ","End":"00:13.755","Text":"rather it\u0027s very often a reactant itself."},{"Start":"00:13.755 ","End":"00:16.590","Text":"What are the 2 main types of reactions mentioned in which"},{"Start":"00:16.590 ","End":"00:19.995","Text":"a water molecule is involved as a reactant?"},{"Start":"00:19.995 ","End":"00:23.730","Text":"Water was mentioned to be a direct participant in these 2 types of"},{"Start":"00:23.730 ","End":"00:27.840","Text":"reactions: hydrolysis reaction and condensation reaction."},{"Start":"00:27.840 ","End":"00:32.400","Text":"Part 2, define these 2 types of reactions and give an example of each."},{"Start":"00:32.400 ","End":"00:35.610","Text":"Water is a direct participant in these 2 types of reactions."},{"Start":"00:35.610 ","End":"00:39.525","Text":"Hydrolysis reaction is the reverse of a condensation reaction."},{"Start":"00:39.525 ","End":"00:42.260","Text":"Hydrolysis reaction is any chemical reaction in which"},{"Start":"00:42.260 ","End":"00:46.400","Text":"a molecule of water breaks 1 or more chemical bonds."},{"Start":"00:46.400 ","End":"00:49.400","Text":"In other words, one in which cleavage,"},{"Start":"00:49.400 ","End":"00:52.190","Text":"accompanied by the addition of water elements occurs,"},{"Start":"00:52.190 ","End":"00:54.590","Text":"and we use the term elements because it isn\u0027t"},{"Start":"00:54.590 ","End":"00:57.350","Text":"the entire water molecule that is added to the other reactants,"},{"Start":"00:57.350 ","End":"01:00.275","Text":"rather it\u0027s the elements H plus and OH minus."},{"Start":"01:00.275 ","End":"01:02.810","Text":"Condensation reaction, on the other hand,"},{"Start":"01:02.810 ","End":"01:05.780","Text":"is one in which the elements of water are eliminated,"},{"Start":"01:05.780 ","End":"01:12.500","Text":"removed from the participating molecules and resulting in water molecules H_2O,"},{"Start":"01:12.500 ","End":"01:15.150","Text":"that is, you could say released."},{"Start":"01:15.150 ","End":"01:19.310","Text":"Now we mentioned the reactions involving ATP and ADP."},{"Start":"01:19.310 ","End":"01:26.150","Text":"An example of a condensation reaction is one in which ADP and inorganic phosphate are"},{"Start":"01:26.150 ","End":"01:30.620","Text":"converted into ATP by"},{"Start":"01:30.620 ","End":"01:34.685","Text":"the elimination of water elements and resulting in a water molecule."},{"Start":"01:34.685 ","End":"01:38.915","Text":"Now the reverse of this is the hydrolysis reaction in which"},{"Start":"01:38.915 ","End":"01:44.300","Text":"ADP is formed by an addition of a water molecule to ATP,"},{"Start":"01:44.300 ","End":"01:48.245","Text":"which breaks it apart into these 2 molecules,"},{"Start":"01:48.245 ","End":"01:50.405","Text":"ATP and organic phosphate."},{"Start":"01:50.405 ","End":"01:54.019","Text":"So what you see here is these reversible reactions."},{"Start":"01:54.019 ","End":"01:58.990","Text":"You have ATP where water is added to it, hydrolysis,"},{"Start":"01:58.990 ","End":"02:05.180","Text":"but breaking apart this molecule so that now you have"},{"Start":"02:05.180 ","End":"02:12.905","Text":"2 molecules and the water was absorbed into these in order to form the 2 molecules."},{"Start":"02:12.905 ","End":"02:15.255","Text":"Whereas on the other hand, if you want,"},{"Start":"02:15.255 ","End":"02:19.526","Text":"consider taking the organic phosphate and the ADP."},{"Start":"02:19.526 ","End":"02:22.385","Text":"In order to combine them together,"},{"Start":"02:22.385 ","End":"02:27.730","Text":"you need to combine the H and the OH from both and release water,"},{"Start":"02:27.730 ","End":"02:32.400","Text":"and now they\u0027ve become 1 larger molecule."}],"ID":29384},{"Watched":false,"Name":"Exercise 32","Duration":"1m 21s","ChapterTopicVideoID":27645,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.085","Text":"Welcome to Water as a Reactant,"},{"Start":"00:02.085 ","End":"00:05.865","Text":"and we are covering an exercise testing our knowledge on this."},{"Start":"00:05.865 ","End":"00:09.945","Text":"Hydrolysis and condensation reactions are the reverse 1 of the other."},{"Start":"00:09.945 ","End":"00:11.610","Text":"With regard to energy investment,"},{"Start":"00:11.610 ","End":"00:15.050","Text":"do they require investment of energy or result in the release of energy,"},{"Start":"00:15.050 ","End":"00:18.105","Text":"and what are the terms relating to energy?"},{"Start":"00:18.105 ","End":"00:23.730","Text":"Hydrolysis reactions, catalyzed by enzymes called hydrolases,"},{"Start":"00:23.730 ","End":"00:26.310","Text":"are almost always exergonic."},{"Start":"00:26.310 ","End":"00:28.755","Text":"By producing 2 molecules from 1,"},{"Start":"00:28.755 ","End":"00:32.685","Text":"they lead to an increase in the randomness of the system."},{"Start":"00:32.685 ","End":"00:36.824","Text":"The formation of cellular polymers from their simple subunits"},{"Start":"00:36.824 ","End":"00:40.790","Text":"by simple reversal of hydrolysis,"},{"Start":"00:40.790 ","End":"00:45.080","Text":"meaning by condensation reactions would be endergonic,"},{"Start":"00:45.080 ","End":"00:48.050","Text":"therefore, does not occur spontaneously."},{"Start":"00:48.050 ","End":"00:49.955","Text":"We can say,"},{"Start":"00:49.955 ","End":"00:53.960","Text":"enzymatic depolymerization, taking a polymer and breaking it apart,"},{"Start":"00:53.960 ","End":"00:59.890","Text":"catalyzed by the enzyme hydrolase, is exergonic,"},{"Start":"00:59.890 ","End":"01:03.800","Text":"while polymerization, creating a polymer,"},{"Start":"01:03.800 ","End":"01:07.775","Text":"a multi-part unit, is endergonic."},{"Start":"01:07.775 ","End":"01:11.000","Text":"Now, reminding you that depolymerization means"},{"Start":"01:11.000 ","End":"01:14.780","Text":"breaking apart molecules with many components into individual components,"},{"Start":"01:14.780 ","End":"01:21.300","Text":"monomers, while polymerization is forming polymers from monomers."}],"ID":29385},{"Watched":false,"Name":"Exercise 33","Duration":"1m 3s","ChapterTopicVideoID":27646,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.435","Text":"We\u0027re in the section of water as a reactant and we are going over an exercise together."},{"Start":"00:06.435 ","End":"00:09.960","Text":"Cells are faced with a thermodynamic obstacle in which"},{"Start":"00:09.960 ","End":"00:13.605","Text":"crucial polymerization reactions are endergonic,"},{"Start":"00:13.605 ","End":"00:16.395","Text":"meaning they require an investment of energy."},{"Start":"00:16.395 ","End":"00:21.045","Text":"How do cells overcome this obstacle in order to form the much-needed polymers?"},{"Start":"00:21.045 ","End":"00:27.060","Text":"There\u0027s an investment of energy that is needed and thus it doesn\u0027t occur spontaneously."},{"Start":"00:27.060 ","End":"00:28.815","Text":"How do the cells overcome this?"},{"Start":"00:28.815 ","End":"00:31.970","Text":"Cells circumvent this thermodynamic obstacle by coupling"},{"Start":"00:31.970 ","End":"00:36.155","Text":"endergonic condensation reactions to exergonic processes,"},{"Start":"00:36.155 ","End":"00:39.290","Text":"such as breakage of the anhydride bond in ATP,"},{"Start":"00:39.290 ","End":"00:44.335","Text":"which results in the release of energy which can then be used to form a polymer."},{"Start":"00:44.335 ","End":"00:53.090","Text":"The idea is to take a reaction that results in the release of energy and then to utilize"},{"Start":"00:53.090 ","End":"01:03.030","Text":"that energy in order to do the polymerization reactions that require energy investment."}],"ID":29386},{"Watched":false,"Name":"Exercise 34","Duration":"1m 49s","ChapterTopicVideoID":27647,"CourseChapterTopicPlaylistID":274667,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.420","Text":"Hi, there. Welcome to another exercise within water as a reactant."},{"Start":"00:04.420 ","End":"00:08.265","Text":"Water and carbon dioxide are the end products of the oxidation of fuels,"},{"Start":"00:08.265 ","End":"00:09.540","Text":"such as glucose,"},{"Start":"00:09.540 ","End":"00:12.555","Text":"while green plants and algae use solar energy,"},{"Start":"00:12.555 ","End":"00:13.770","Text":"the energy of sunlight,"},{"Start":"00:13.770 ","End":"00:17.985","Text":"along with water molecules in the process of photosynthesis."},{"Start":"00:17.985 ","End":"00:20.145","Text":"Show these 2 reactions."},{"Start":"00:20.145 ","End":"00:23.400","Text":"Water and carbon dioxide are the end products of the oxidation of fuels."},{"Start":"00:23.400 ","End":"00:26.040","Text":"We said glucose is an example of this,"},{"Start":"00:26.040 ","End":"00:28.020","Text":"and this is glucose,"},{"Start":"00:28.020 ","End":"00:36.289","Text":"C_6H_12O_6 plus oxygen results in carbon dioxide and water."},{"Start":"00:36.289 ","End":"00:44.390","Text":"This water and carbon are the products of the oxidation of fuels."},{"Start":"00:44.390 ","End":"00:47.120","Text":"We also mentioned that the metabolic water"},{"Start":"00:47.120 ","End":"00:49.910","Text":"formed by oxidation of foods and stored fats is actually"},{"Start":"00:49.910 ","End":"00:55.820","Text":"enough to allow some animals in very dry habitats like kangaroos,"},{"Start":"00:55.820 ","End":"00:59.795","Text":"camels, etc., to survive extended periods without drinking of water."},{"Start":"00:59.795 ","End":"01:06.380","Text":"This water hydrates organisms that need that in dry arid environment."},{"Start":"01:06.380 ","End":"01:10.190","Text":"Now, green plants and algae use solar energy, light energy,"},{"Start":"01:10.190 ","End":"01:14.300","Text":"to split water in the process of photosynthesis."},{"Start":"01:14.300 ","End":"01:19.080","Text":"You have the reaction as being 2H_2O plus"},{"Start":"01:19.080 ","End":"01:25.570","Text":"2A light investment results in O_2 and 2AH_2."},{"Start":"01:25.570 ","End":"01:27.425","Text":"Now in this reaction,"},{"Start":"01:27.425 ","End":"01:30.795","Text":"A is an electron accepting species."},{"Start":"01:30.795 ","End":"01:37.020","Text":"It represents a species that accepts electrons during the process in photosynthesis,"},{"Start":"01:37.020 ","End":"01:40.505","Text":"and this varies with the type of photosynthetic organism."},{"Start":"01:40.505 ","End":"01:43.880","Text":"Water is the electron donor in"},{"Start":"01:43.880 ","End":"01:49.440","Text":"an oxidation-reduction sequence that is fundamental to all life."}],"ID":29387}],"Thumbnail":null,"ID":274667},{"Name":"Biological Aspects of Water","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Fitness of the Aqueous Environment for Living Organisms","Duration":"3m 39s","ChapterTopicVideoID":28178,"CourseChapterTopicPlaylistID":277601,"HasSubtitles":true,"ThumbnailPath":"https://www.proprep.uk/Images/Videos_Thumbnails/28178.jpeg","UploadDate":"2021-12-25T11:29:51.0100000","DurationForVideoObject":"PT3M39S","Description":null,"MetaTitle":"Fitness of the Aqueous Environment for Living Organisms: Video + Workbook | Proprep","MetaDescription":"Water - Biological Aspects of Water. Watch the video made by an expert in the field. Download the workbook and maximize your learning.","Canonical":"https://www.proprep.uk/general-modules/all/biochemistry/water/biological-aspects-of-water/vid29412","VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.360","Text":"Hi there. Welcome to biological aspects of water."},{"Start":"00:03.360 ","End":"00:07.755","Text":"We will be talking about fitness of the aqueous environment for living organisms."},{"Start":"00:07.755 ","End":"00:10.500","Text":"Now, it\u0027s going to be taking all the information we learned about"},{"Start":"00:10.500 ","End":"00:14.655","Text":"water and seeing how it enables life."},{"Start":"00:14.655 ","End":"00:15.840","Text":"By the end of the section,"},{"Start":"00:15.840 ","End":"00:19.695","Text":"you\u0027ll be able to describe the properties of water that contribute to biological life,"},{"Start":"00:19.695 ","End":"00:23.055","Text":"and how organisms utilize water\u0027s properties for their benefit."},{"Start":"00:23.055 ","End":"00:25.545","Text":"As mentioned early on in the course,"},{"Start":"00:25.545 ","End":"00:27.390","Text":"life likely started in the water,"},{"Start":"00:27.390 ","End":"00:31.130","Text":"so organisms have effectively adapted to"},{"Start":"00:31.130 ","End":"00:33.620","Text":"their aqueous environment and have evolved"},{"Start":"00:33.620 ","End":"00:36.365","Text":"means of exploiting the unusual properties of water."},{"Start":"00:36.365 ","End":"00:39.410","Text":"Water, which requires great energy investment to"},{"Start":"00:39.410 ","End":"00:42.770","Text":"raise its temperature of 1 gram by 1 Celsius,"},{"Start":"00:42.770 ","End":"00:45.665","Text":"essentially acts as a heat buffer,"},{"Start":"00:45.665 ","End":"00:51.380","Text":"keeping the temperature of an organism relatively constant as the temperature of"},{"Start":"00:51.380 ","End":"00:54.980","Text":"the surrounding fluctuates and as heat is generated as"},{"Start":"00:54.980 ","End":"00:58.850","Text":"a byproduct of metabolism within the organism."},{"Start":"00:58.850 ","End":"01:04.400","Text":"Furthermore, some vertebrates exploit the high heat of vaporization of water by"},{"Start":"01:04.400 ","End":"01:11.035","Text":"using this losing excess body heat to evaporate sweat."},{"Start":"01:11.035 ","End":"01:12.920","Text":"This is how humans,"},{"Start":"01:12.920 ","End":"01:15.230","Text":"for example, stay cool."},{"Start":"01:15.230 ","End":"01:20.540","Text":"Other cases are dogs where they basically do this by their panting,"},{"Start":"01:20.540 ","End":"01:22.505","Text":"with their tongue out when they go;"},{"Start":"01:22.505 ","End":"01:29.254","Text":"they are actually allowing also the heat to be released by this action."},{"Start":"01:29.254 ","End":"01:34.730","Text":"The high degree of internal cohesion of liquid water due to hydrogen bonding is"},{"Start":"01:34.730 ","End":"01:41.190","Text":"utilized by plants for transporting dissolved nutrients from the roots to the leaves."},{"Start":"01:41.190 ","End":"01:46.745","Text":"You have water and nutrients in the soil that need to be transported"},{"Start":"01:46.745 ","End":"01:52.685","Text":"up to the leaves in order to do photosynthesis, respiration, etc."},{"Start":"01:52.685 ","End":"01:54.125","Text":"Here what you see,"},{"Start":"01:54.125 ","End":"01:55.820","Text":"you have these water molecules."},{"Start":"01:55.820 ","End":"02:00.095","Text":"Here is the H to the oxygen,"},{"Start":"02:00.095 ","End":"02:02.690","Text":"the H here are the hydrogens in white,"},{"Start":"02:02.690 ","End":"02:04.190","Text":"and you have the oxygen and center."},{"Start":"02:04.190 ","End":"02:09.125","Text":"You see several of them and they interact hydrogen bond with each other,"},{"Start":"02:09.125 ","End":"02:17.225","Text":"and pull each other up as they go up the stem to the leaves and the rest of the plant."},{"Start":"02:17.225 ","End":"02:21.590","Text":"Even the density of ice which is lower than that of"},{"Start":"02:21.590 ","End":"02:25.460","Text":"liquid water has important biological consequences"},{"Start":"02:25.460 ","End":"02:27.875","Text":"of the life cycles of aquatic organism."},{"Start":"02:27.875 ","End":"02:29.990","Text":"Ponds freeze from the top down,"},{"Start":"02:29.990 ","End":"02:35.060","Text":"and the layer of ice at the top insulates the water below from frigid air preventing"},{"Start":"02:35.060 ","End":"02:40.850","Text":"the pond and the organisms in it from freezing solid at the lower levels as well,"},{"Start":"02:40.850 ","End":"02:47.120","Text":"and this allows for fish to survive and swim below the ice layer."},{"Start":"02:47.120 ","End":"02:50.540","Text":"Most fundamental to all organisms is the fact that"},{"Start":"02:50.540 ","End":"02:54.800","Text":"many physical and biological properties of cell macromolecules,"},{"Start":"02:54.800 ","End":"02:58.790","Text":"particularly the proteins and nucleic acids derive from"},{"Start":"02:58.790 ","End":"03:04.440","Text":"their interactions with water molecules of the surrounding medium."},{"Start":"03:04.440 ","End":"03:06.650","Text":"The influence of water on the course of"},{"Start":"03:06.650 ","End":"03:11.525","Text":"biological evolution has been profound and determinative."},{"Start":"03:11.525 ","End":"03:14.450","Text":"If life forms have evolved elsewhere in the universe,"},{"Start":"03:14.450 ","End":"03:18.515","Text":"they are unlikely to resemble those of Earth unless they\u0027re extraterrestrial."},{"Start":"03:18.515 ","End":"03:24.970","Text":"Origin is also a place in which plentiful liquid water is available."},{"Start":"03:24.970 ","End":"03:26.780","Text":"With this, we have completed"},{"Start":"03:26.780 ","End":"03:31.325","Text":"this section going over fitness of the aqueous environment for living organisms."},{"Start":"03:31.325 ","End":"03:35.180","Text":"You should describe properties of water that contribute to biological life,"},{"Start":"03:35.180 ","End":"03:39.900","Text":"and how organisms utilize water\u0027s properties for their benefits."}],"ID":29412},{"Watched":false,"Name":"Exercise 1","Duration":"47s","ChapterTopicVideoID":28179,"CourseChapterTopicPlaylistID":277601,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.490","Text":"Hi there. Welcome to the exercise portion of"},{"Start":"00:02.490 ","End":"00:06.165","Text":"Fitness of the Aqueous Environment for Living Organisms."},{"Start":"00:06.165 ","End":"00:08.835","Text":"It can be said that water acts as a heat buffer."},{"Start":"00:08.835 ","End":"00:13.350","Text":"What does this mean, and how does this contribute to viability of organisms?"},{"Start":"00:13.350 ","End":"00:16.770","Text":"Water, which requires great energy investment to"},{"Start":"00:16.770 ","End":"00:20.295","Text":"raise its temperature of 1 gram by 1 degree Celsius,"},{"Start":"00:20.295 ","End":"00:22.350","Text":"essentially acts as a heat buffer keeping"},{"Start":"00:22.350 ","End":"00:25.125","Text":"the temperature of an organism relatively constant,"},{"Start":"00:25.125 ","End":"00:27.945","Text":"even if the temperature of the surroundings fluctuate,"},{"Start":"00:27.945 ","End":"00:30.520","Text":"and though heat is generated as a byproduct of"},{"Start":"00:30.520 ","End":"00:35.145","Text":"organisms\u0027 metabolism within their cells and their own environment."},{"Start":"00:35.145 ","End":"00:39.240","Text":"Furthermore, some vertebrates exploit the high heat of vaporization of water"},{"Start":"00:39.240 ","End":"00:43.350","Text":"by using excess body heat to evaporate sweat,"},{"Start":"00:43.350 ","End":"00:46.660","Text":"like in the case of humans."}],"ID":29413},{"Watched":false,"Name":"Exercise 2","Duration":"31s","ChapterTopicVideoID":28176,"CourseChapterTopicPlaylistID":277601,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.550","Text":"Hi, welcome back to another exercise covering"},{"Start":"00:02.550 ","End":"00:06.570","Text":"this section of Fitness of Aqueous Environment for Living Organisms."},{"Start":"00:06.570 ","End":"00:11.325","Text":"Explain how water in solid form is inducive of aquatic life."},{"Start":"00:11.325 ","End":"00:13.980","Text":"Water in solid form is ice."},{"Start":"00:13.980 ","End":"00:15.300","Text":"The density of ice,"},{"Start":"00:15.300 ","End":"00:17.210","Text":"which is lower than that of liquid water,"},{"Start":"00:17.210 ","End":"00:20.760","Text":"results in the liquid environment to freeze from the top down."},{"Start":"00:20.760 ","End":"00:22.890","Text":"This results in a layer of ice at the top"},{"Start":"00:22.890 ","End":"00:25.140","Text":"which insulates the water below from frigid air,"},{"Start":"00:25.140 ","End":"00:26.880","Text":"preventing the body of water,"},{"Start":"00:26.880 ","End":"00:31.630","Text":"and thus the organisms in it from freezing solid."}],"ID":29414},{"Watched":false,"Name":"Exercise 3","Duration":"45s","ChapterTopicVideoID":28177,"CourseChapterTopicPlaylistID":277601,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.610","Text":"Welcome to an exercise on Fitness of Aqueous Environment for Living Organisms."},{"Start":"00:05.610 ","End":"00:10.500","Text":"Describe a way that hydrogen bonding of water molecules contributes to plants\u0027 viability."},{"Start":"00:10.500 ","End":"00:13.980","Text":"Hydrogen bonding between water molecules results in cohesion."},{"Start":"00:13.980 ","End":"00:17.640","Text":"This high degree of internal cohesion of liquid water is utilized by plants"},{"Start":"00:17.640 ","End":"00:21.405","Text":"for transporting dissolved nutrients from the roots to the leaves,"},{"Start":"00:21.405 ","End":"00:23.505","Text":"which enables its function and growth."},{"Start":"00:23.505 ","End":"00:26.430","Text":"You see here the depiction of the water molecules,"},{"Start":"00:26.430 ","End":"00:27.510","Text":"you have the oxygen in red,"},{"Start":"00:27.510 ","End":"00:29.310","Text":"and the 2 hydrogens in white,"},{"Start":"00:29.310 ","End":"00:32.394","Text":"and as they move and they go up the stem,"},{"Start":"00:32.394 ","End":"00:35.765","Text":"they pull each other because of this cohesion,"},{"Start":"00:35.765 ","End":"00:37.970","Text":"and then they can go against gravity,"},{"Start":"00:37.970 ","End":"00:45.870","Text":"and move up to provide nutrition and water to the leaves and branches up top."}],"ID":29415}],"Thumbnail":null,"ID":277601}]

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