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This is mRNA we're talking about right over here. This is mRNA, but there's another type of RNA called tRNA that essentially brings these two characters together. So the tRNA, and I'm just gonna, it's got some structure here, I'm not drawing it completely right, but it's going to match right over here where maybe it ha... | DNA replication and RNA transcription and translation Khan Academy.mp3 |
And on this end, it was attached to this amino acid, and so it matches them together. And then you're gonna have another tRNA that might attach to amino acid two, which I will do in purple, amino acid two. And that just happens to coincide with, so it can complement right over here, so it attaches in the right place. S... | DNA replication and RNA transcription and translation Khan Academy.mp3 |
So it's A, a U right over here, this tRNA. And so it'll construct the sequence of amino acids. And as you put these amino acids together, then you are actually constructing a protein. So a protein is essentially a bunch of, a sequence of these amino acids put together. So a sequence of these amino acids put together. A... | DNA replication and RNA transcription and translation Khan Academy.mp3 |
So a protein is essentially a bunch of, a sequence of these amino acids put together. So a sequence of these amino acids put together. And these proteins are essentially the molecules that run life for the most part. Obviously, if you eat an animal, it's going to be made up of fat and sugars and proteins, but the prote... | DNA replication and RNA transcription and translation Khan Academy.mp3 |
What I want to do in this video is explore the idea of allele frequency. Allele frequency. And just as a reminder, an allele is a variant of a gene. You get a variant of a gene from your mother and you get another variant of the gene from the father. And so when we're talking about the allele, we're talking about that ... | Allele frequency.mp3 |
You get a variant of a gene from your mother and you get another variant of the gene from the father. And so when we're talking about the allele, we're talking about that specific variant that you got from your mother or your father. And we've seen this before. But now let's dig a little bit deeper. And to help us get ... | Allele frequency.mp3 |
But now let's dig a little bit deeper. And to help us get our heads around this, we'll start with a fairly common model for this. And we're gonna think about eye color. And obviously this is a very large simplification. But let's just assume that we have a population where there's only two variants of an eye color gene... | Allele frequency.mp3 |
And obviously this is a very large simplification. But let's just assume that we have a population where there's only two variants of an eye color gene. Let's first assume there is an eye color gene and let's assume there's two variants. One variant, one allele for eye color, we'll use the shorthand capital B. Let's sa... | Allele frequency.mp3 |
One variant, one allele for eye color, we'll use the shorthand capital B. Let's say that's the allele for brown. Brown eye color. And we're gonna assume that this one is dominant. It's dominant over the other allele. Now the other allele, we're gonna assume, is for blue eye color. And we'll represent that with a lowerc... | Allele frequency.mp3 |
And we're gonna assume that this one is dominant. It's dominant over the other allele. Now the other allele, we're gonna assume, is for blue eye color. And we'll represent that with a lowercase b. So that is blue eye color. And we're going to assume that this is recessive. So once again, this is review. | Allele frequency.mp3 |
And we'll represent that with a lowercase b. So that is blue eye color. And we're going to assume that this is recessive. So once again, this is review. Someone who has one of the big B alleles, the brown alleles. It doesn't matter what their other allele is going to be because it's either gonna be another brown or it'... | Allele frequency.mp3 |
So once again, this is review. Someone who has one of the big B alleles, the brown alleles. It doesn't matter what their other allele is going to be because it's either gonna be another brown or it's going to be a blue. They're going to show brown eyes. So this is going to be brown eyes. And this is going to be brown e... | Allele frequency.mp3 |
They're going to show brown eyes. So this is going to be brown eyes. And this is going to be brown eyes because the capital B is dominant. The only way to get blue eyes is to be, the only way to have blue eyes is to be a homozygote for the recessive allele. And all of that, of course, is review. We've seen that before.... | Allele frequency.mp3 |
The only way to get blue eyes is to be, the only way to have blue eyes is to be a homozygote for the recessive allele. And all of that, of course, is review. We've seen that before. But now let's think about allele frequency. And to think about that, I'll set up a very artificially small population. So let's say our po... | Allele frequency.mp3 |
But now let's think about allele frequency. And to think about that, I'll set up a very artificially small population. So let's say our population has exactly two people in it. Population has exactly two people in it, person one and person two. And let's say we're able to look into their DNA and figure out their genoty... | Allele frequency.mp3 |
Population has exactly two people in it, person one and person two. And let's say we're able to look into their DNA and figure out their genotypes. So person one, let's say, has a capital B allele, has a brown allele and a blue allele. While person two has two blue alleles. Now given that we know the genotypes in this ... | Allele frequency.mp3 |
While person two has two blue alleles. Now given that we know the genotypes in this artificially small population, now we can start thinking about the allele frequencies or the frequencies of the different alleles. So what do you think is going to be the frequency, the frequency of the brown allele in this population? ... | Allele frequency.mp3 |
And I encourage you to pause this video and think about this on your own. So I'm assuming you've had a go at it. So you might be tempted to say, oh, well it looks like one out of two people have it, maybe it's 50%. But that wouldn't be the right way to think about allele frequencies. And allele frequencies, you wanna d... | Allele frequency.mp3 |
But that wouldn't be the right way to think about allele frequencies. And allele frequencies, you wanna dig a little bit deeper and look at the individual alleles. And when you look at that, you say, okay, there's four individual alleles in this population of, or there's four variants in this, or there's literally four... | Allele frequency.mp3 |
And out of them, one of them carry, one of them is the capital B, is the capital B allele. And so we could say that that is going to be 0.25, or 25%. So once again, 20, 25% of the genes for eye color have the capital B allele, have the brown allele. Now we can do the same, we can ask ourselves the same question for the... | Allele frequency.mp3 |
Now we can do the same, we can ask ourselves the same question for the lowercase b allele. What fraction of the genes in this population are code for or represent the lowercase b, the blue allele? And once again, I encourage you to pause the video and think about it. Well, very similar idea. There's four genes in the p... | Allele frequency.mp3 |
Well, very similar idea. There's four genes in the population that are coding for eye color. Of them, one, two, three, one, two, three, code for or are the lowercase blue, are the lowercase blue allele. So that's 0.75, or 75%. 75% of the genes code for the lowercase, the blue allele, while 25 are the brown, are the bro... | Allele frequency.mp3 |
So that's 0.75, or 75%. 75% of the genes code for the lowercase, the blue allele, while 25 are the brown, are the brown allele. And I really wanna hit this point home, how this is different than, say, the phenotype frequency. If I asked you in the population, if I asked you the percent of brown-eyed people, brown-eyed ... | Allele frequency.mp3 |
If I asked you in the population, if I asked you the percent of brown-eyed people, brown-eyed people, so now I'm talking about phenotype, what would that be? Well, there's two people in the population, one of them is exhibiting brown eyes, so that's going to be 1.5. And similarly, if I were to ask you what is the perce... | Allele frequency.mp3 |
That too would be 1.5. This person is one of the two people, they're exhibiting blue eyes. But allele frequency, we're digging deeper. We're looking at the genotypes, and we're saying, well, out of the four genes here, one of them is the big B allele, so that's 25%, so 25% of the gene population codes for, is the brown... | Allele frequency.mp3 |
We're looking at the genotypes, and we're saying, well, out of the four genes here, one of them is the big B allele, so that's 25%, so 25% of the gene population codes for, is the brown allele, and 75% is the blue allele. And this is really important to internalize, because once we internalize this, then as we'll see, ... | Allele frequency.mp3 |
We can denote this, and this is just a convention that's often used, by the lowercase letter p, and we can use q, lowercase q, to denote the frequency. So p, lowercase p, is the frequency of the dominant allele, lowercase q, the frequency of the recessive allele. But what's true here? What's true of p, what's true, wha... | Allele frequency.mp3 |
What's true of p, what's true, what's going to be true of p plus q? What's going to be, what's p plus q going to be equal to? And I encourage you to pause the video again, and think about that. What is this going to be equal to? Well, when we started off, we said that there's only two potential, that's one of the assum... | Allele frequency.mp3 |
What is this going to be equal to? Well, when we started off, we said that there's only two potential, that's one of the assumptions we assumed. We assumed there's only two alleles in this population, and kind of the allele population for this, and this gene population for this trait. So the frequency of the dominant o... | Allele frequency.mp3 |
Well, if we were to look at a cell membrane, and just to be clear what we're looking at, if this is a cell right over here, if this is a cell, and this is its membrane, this is the membrane, it's kind of what keeps the cell, the inside of the cell separated from whatever is outside the cell, we're looking at a cross se... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
This is outside. And when you zoom in, when you zoom in, this little part right over here, this is actually a phospholipid bilayer that forms it. And so when you hear that, you might say, well, what is a phospholipid? And that's a good question, because when you understand what a phospholipid is, it starts to make sens... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And that's a good question, because when you understand what a phospholipid is, it starts to make sense why it would form a bilayer like this, and why it's the basis for so many membranes in biological systems. So this is indicative of a phospholipid. And as its name implies, and let me write that down, this is a phosp... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And in general, the word lipid, and we have a whole video on lipids, means something that doesn't dissolve so well in water. And that's true as the case of this phospholipid. You have these hydrocarbon tails that are coming from fatty acids. And so these hydrocarbon tails, they have no obvious charge or no obvious pola... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And so these hydrocarbon tails, they have no obvious charge or no obvious polarity. We know that water's a polar molecule. That's what gives us its hydrogen bonds, and it's attracted to itself. But these don't have those, and so they're not going to be attracted to the water, and the water's not going to be attracted t... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
But these don't have those, and so they're not going to be attracted to the water, and the water's not going to be attracted to them. And so these tails are hydrophobic. So you have hydrophobic, hydrophobic tails. And these are really kind of the lipid part of the phospholipids. And then you have the phosphate head. Yo... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And these are really kind of the lipid part of the phospholipids. And then you have the phosphate head. You have the phosphate head right over here. And as you can clearly see, this has some charge. Charged molecules do well in polar substances like water. They're going to dissolve well. And so this part right over her... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And as you can clearly see, this has some charge. Charged molecules do well in polar substances like water. They're going to dissolve well. And so this part right over here is going to be hydrophilic. And actually, molecules that have a hydrophilic part and a hydrophobic part, there's a special word for them. Amphipath... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And so this part right over here is going to be hydrophilic. And actually, molecules that have a hydrophilic part and a hydrophobic part, there's a special word for them. Amphipathic, a word that I sometimes have trouble saying. So phospholipids are amphipathic, amphipathic, which means that they have both a hydrophili... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
So phospholipids are amphipathic, amphipathic, which means that they have both a hydrophilic end, a part that is attracted to water, and a hydrophobic end that is not attracted to water. And hopefully that starts to explain why they organize themselves in this way. Because you can imagine, the hydrophilic heads are goi... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And the tails are hydrophobic. The water's going to go away from them, or they're going to go away from the water. And so they're just going to face each other, and they're going to be on the inside of the membrane. But the really cool thing is a structure like this, having this amphipathic molecule, allows things like... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
But the really cool thing is a structure like this, having this amphipathic molecule, allows things like these lipid bilayers, I should say, to form. And it's actually fascinating, we think, that if you go far back enough, even before life in cellular form formed, that you might have had phospholipids spontaneously for... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
Let me see if I can draw it relatively neatly. So I think I'll draw half of it, just because you get, well, I'll draw the whole thing. Hopefully you get the idea. So that would be one layer of the phosphate heads facing the outside. This is the inner layer. And I'm doing a cross section right over here. And then you ha... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
So that would be one layer of the phosphate heads facing the outside. This is the inner layer. And I'm doing a cross section right over here. And then you have your hydrophobic tails. So your hydrophobic tails, let me do that in a different color. So your hydrophobic tails, I think you get the picture. We have a bunch ... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And then you have your hydrophobic tails. So your hydrophobic tails, let me do that in a different color. So your hydrophobic tails, I think you get the picture. We have a bunch of hydrophobic tails on either end. And then you could spontaneously form a structure like this which starts to feel like, hey, well, maybe th... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
We have a bunch of hydrophobic tails on either end. And then you could spontaneously form a structure like this which starts to feel like, hey, well, maybe there's a protocell forming. And obviously to actually have real life, you have to have some form of information that can be passed on. And you have to have some ty... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And you have to have some type of metabolism. And the cell is living in all of the definitions of life. But at least this basic structure of the cellular membrane, you can imagine how it forms in a pre-life state even by virtue of amphipathic molecules like a phospholipid. So fair enough. We're able to form this phosph... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
So fair enough. We're able to form this phospholipid bilayer. But what are all these other things that I have drawn here? Well, these are proteins. And these are examples of, so this is a protein right over here. This is a protein. This is a protein. | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
Well, these are proteins. And these are examples of, so this is a protein right over here. This is a protein. This is a protein. And I just drew some kind of blobs to be indicative of the variety of proteins. But the important thing to realize is, is when you think of cells, there's all of this diversity. There's all o... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
This is a protein. And I just drew some kind of blobs to be indicative of the variety of proteins. But the important thing to realize is, is when you think of cells, there's all of this diversity. There's all of this complexity that is on or embedded inside of its membrane. So instead of just thinking of it just kind o... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
There's all of this complexity that is on or embedded inside of its membrane. So instead of just thinking of it just kind of as a uniform phospholipid bilayer, there's all sorts of stuff. There's all sorts of stuff. Maybe if we view this as a cross section, there's all sorts of stuff embedded in it. And we see it right... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
Maybe if we view this as a cross section, there's all sorts of stuff embedded in it. And we see it right over here in this diagram. You could say there's a mosaic of things embedded in it. A mosaic is a picture made up of a bunch of different components of all different colors. And you can see that you have all differe... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
A mosaic is a picture made up of a bunch of different components of all different colors. And you can see that you have all different different components here, different types of proteins. You have proteins like this that go across the membrane. We call these transmembrane proteins. They're a special class of integral... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
We call these transmembrane proteins. They're a special class of integral proteins. You have integral proteins like this that might only interact with one part of the bilayer, while these kind of go across it. You have things like glycolipids. So this right over here, this is a glycolipid. Glycolipid, which is fascinat... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
You have things like glycolipids. So this right over here, this is a glycolipid. Glycolipid, which is fascinating. It lodges itself in the membrane because it has this lipid end. So that's going to be hydrophobic. It's going to get along with all of the other hydrophobic things. But then it has an end that's really a, ... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
It lodges itself in the membrane because it has this lipid end. So that's going to be hydrophobic. It's going to get along with all of the other hydrophobic things. But then it has an end that's really a, that's a chain of sugars. And that part is going to be hydrophilic. It's going to sit outside of the cell. And thes... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
But then it has an end that's really a, that's a chain of sugars. And that part is going to be hydrophilic. It's going to sit outside of the cell. And these chains of sugars, these are actually key for cell-cell recognition. Our immune system uses these to differentiate between which cells are the ones that are actuall... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And these chains of sugars, these are actually key for cell-cell recognition. Our immune system uses these to differentiate between which cells are the ones that are actually from my body, the ones that I don't want to mess with, the ones I want to protect, and which cells are the ones that are foreign, the ones that I... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And there's all sorts of, and that's not all we're talking about when we talk about glycolipids as kind of a way for cells to be recognized or to be tagged in different ways. So it's a fascinating thing that these chains of sugars can lead to such complex behavior, and frankly, such useful behavior from our point of vi... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
This right over here is an example of a glycoprotein. Glycoprotein. And as you can see, when you put all this stuff together, you get a mosaic. And I'm actually not even done there. You have things like cholesterol embedded. Cholesterol is a lipid, so it's gonna sit in the hydrophobic part of the membrane, and that act... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And I'm actually not even done there. You have things like cholesterol embedded. Cholesterol is a lipid, so it's gonna sit in the hydrophobic part of the membrane, and that actually helps with the fluidity of the membrane, making sure it's not too fluid or not too stiff. So this is cholesterol. Cholesterol right over t... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
So this is cholesterol. Cholesterol right over there. So you see this mosaic of stuff, but what about the fluid part? And I just talked about cholesterol's value and making sure that it's just the right amount of fluidity. What's neat about this is this isn't a rigid structure. If this thing were to be jostled around a... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
And I just talked about cholesterol's value and making sure that it's just the right amount of fluidity. What's neat about this is this isn't a rigid structure. If this thing were to be jostled around a little bit or maybe it would be plucked out somehow, the phospholipids would just spontaneously rearrange to fill in ... | Fluid mosaic model of cell membranes Biology Khan Academy.mp3 |
One end has a partially negative charge, and the other end has partially positive charges. And we talked about how this leads to hydrogen bonds. And we alluded to the fact that, hey, maybe these hydrogen bonds give us all sorts of neat properties of water. And what I want to talk about in this video is one of those ver... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And what I want to talk about in this video is one of those very important properties, and that's water's ability to be a solvent. And this means that it's easy for certain things to be dissolved inside of water. And that's super important because that's how a lot of the chemistry occurs, by things getting dissolved in... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And this is actually what's happening inside of cells in the cytoplasm. The cytoplasm, which is mostly water, is a solvent which allows a bunch of interactions to happen between different types of molecules. But let's think about why water is a good solvent and what types of things it can dissolve easily and what types... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So the key feature that makes water a good solvent, or at least a good solvent for a large class of molecules, is its polarity. If I were to take some sodium chloride, often known as table salt, if I were to take sodium NaCl, sodium chloride, the sodium and chloride are attracted by ionic bonds. The sodium right over h... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
It has an electron stripped from it. And the chloride has a... Let me write that in a different color. So the sodium has a positive charge because it has an electron stripped from it. And the chloride is an anion. It has a negative charge. It is a negatively charged ion because it gains an extra electron. So they're at... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And the chloride is an anion. It has a negative charge. It is a negatively charged ion because it gains an extra electron. So they're attracted to each other. This has a positive charge. This has a negative charge. This is called an ionic bond. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So they're attracted to each other. This has a positive charge. This has a negative charge. This is called an ionic bond. But if you put sodium chloride in water, something very interesting happens. This is something that we've all experienced. Take some table salt and put it in water and see what happens. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
This is called an ionic bond. But if you put sodium chloride in water, something very interesting happens. This is something that we've all experienced. Take some table salt and put it in water and see what happens. It will dissolve. And why does it dissolve? Well, let's draw it out. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Take some table salt and put it in water and see what happens. It will dissolve. And why does it dissolve? Well, let's draw it out. So this is the sodium right over here. So that's the sodium. It has a positive charge. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Well, let's draw it out. So this is the sodium right over here. So that's the sodium. It has a positive charge. And then this is the chloride right over here. It has a negative charge. What's going to happen if you put it inside of the water? | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
It has a positive charge. And then this is the chloride right over here. It has a negative charge. What's going to happen if you put it inside of the water? Let me do that negative charge in the green. What's going to happen when you put it inside of water? Well, you can imagine. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
What's going to happen if you put it inside of the water? Let me do that negative charge in the green. What's going to happen when you put it inside of water? Well, you can imagine. The negative ends of the water molecules are going to be attracted to the sodium ion. So it's going to look something like this. So you ha... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Well, you can imagine. The negative ends of the water molecules are going to be attracted to the sodium ion. So it's going to look something like this. So you have the oxygen. So you have the oxygen. Oxygen. Oxygen. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So you have the oxygen. So you have the oxygen. Oxygen. Oxygen. Oxygen. Oxygen. I'm clearly not drawing things to scale, but this will just give you the idea. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Oxygen. Oxygen. Oxygen. I'm clearly not drawing things to scale, but this will just give you the idea. This end of the water molecule all has a partially negative charge. Partially negative charge. So it's going to be attracted to the positive sodium ion. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
I'm clearly not drawing things to scale, but this will just give you the idea. This end of the water molecule all has a partially negative charge. Partially negative charge. So it's going to be attracted to the positive sodium ion. And then the hydrogen ends are going to have a partial positive charge. And then they're... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So it's going to be attracted to the positive sodium ion. And then the hydrogen ends are going to have a partial positive charge. And then they're going to be repelled. They are going to be repelled from the positive sodium ion. So it's going to look something like this. It's going to look something like this. You're g... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
They are going to be repelled from the positive sodium ion. So it's going to look something like this. It's going to look something like this. You're going to have partial positive charge on the outside. Partial positive charge on the outside. And now these hydrogens over here, this will just interact with water the wa... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
You're going to have partial positive charge on the outside. Partial positive charge on the outside. And now these hydrogens over here, this will just interact with water the way that it would typically with the hydrogen bonding the molecules just flowing past each other. So the fact that the sodium ion here it's an io... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So the fact that the sodium ion here it's an ion. It has charge. It is able to dissolve in the water very easily because it is attracted to the partially negative ends of the water molecule. Now a similar thing is going to happen with the chloride ion. And we call a negative ion an anion. So over here, and actually let... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Now a similar thing is going to happen with the chloride ion. And we call a negative ion an anion. So over here, and actually let me move it over a little bit so that I have some space. So the chloride anion let me move it over a little bit. So right, maybe I'll move it over maybe I'll move it right over here. So the c... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So the chloride anion let me move it over a little bit. So right, maybe I'll move it over maybe I'll move it right over here. So the chloride anion let me see, I'm having trouble with my selection tool. Alright, so there we go. The chloride anion, it has a negative charge so it's going to be attracted to the positive e... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Alright, so there we go. The chloride anion, it has a negative charge so it's going to be attracted to the positive end of the water molecules. So you can imagine something like this. So the hydrogen ends are going to be attracted to it. They have a partially positive charge. They have a partially positive charge. Of c... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So the hydrogen ends are going to be attracted to it. They have a partially positive charge. They have a partially positive charge. Of course you have the oxygen end that has a partially negative charge. It has a partially negative charge. And I could draw more of these hydrogen, hydrogen attracted there. You have the ... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Of course you have the oxygen end that has a partially negative charge. It has a partially negative charge. And I could draw more of these hydrogen, hydrogen attracted there. You have the oxygen over, let me do that I want to keep my colors consistent. The oxygen right over there. You have the hydrogen. Once again, thi... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
You have the oxygen over, let me do that I want to keep my colors consistent. The oxygen right over there. You have the hydrogen. Once again, this isn't drawn to scale. Hydrogen it is bonded to the oxygen. And so once again, you can form this, I guess you can almost imagine this shell of water molecules is going to be ... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Once again, this isn't drawn to scale. Hydrogen it is bonded to the oxygen. And so once again, you can form this, I guess you can almost imagine this shell of water molecules is going to be attracted to it. It's going to be attracted or I guess you could say the partially positive end which is where the hydrogen atoms ... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
It's going to be attracted or I guess you could say the partially positive end which is where the hydrogen atoms are is what's going to be attracted to this negative ion. So this is partial positive over here. And then on the partially negative side outside of this shell, you can imagine it's just going to interact wit... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And so it's going to be able to flow very easily. So you probably see something interesting here. If something has charge if it's an ion or if something has some polarity it's very easy to dissolve it inside of water. And in this case, and just to have some terminology here in this case, water is the solvent so water i... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And in this case, and just to have some terminology here in this case, water is the solvent so water is the solvent so the solvent is water and the thing that's being dissolved in the water, we call that a solute. So we call this the solute. So the sodium chloride that is, you could use sodium chloride as a solute or y... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
And so you say, well what kind of things dissolve well? Well things that have charge or that are polar. And things that are charged and polar and tend to dissolve well in water there's another word we use for them. We say that they are hydrophilic. So we could say that this right over here is hydrophilic. And if you lo... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
We say that they are hydrophilic. So we could say that this right over here is hydrophilic. And if you look at the word roots, hydro is referring to water. So hydro is referring to water and philic means loving. So this literally means water loving. Water loving. Hydrophilic. | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So hydro is referring to water and philic means loving. So this literally means water loving. Water loving. Hydrophilic. And so you might be asking, ok everything we've talked about, we've seen water molecules, that's polar we're looking at charged ions, ok we can get that we can get why they would be hydrophilic, they... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Hydrophilic. And so you might be asking, ok everything we've talked about, we've seen water molecules, that's polar we're looking at charged ions, ok we can get that we can get why they would be hydrophilic, they can incorporate themselves well into the water. But what are examples of things that would not incorporate ... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Well in general things that don't have charge or that aren't polar aren't going to be able to dissolve in water all that well. And a good example is hydrocarbons. So if you took some hexane, and hexane is a major constituent of car gasoline. So hexane, hex the prefix means six carbons. So let's see one let me do this i... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So hexane, hex the prefix means six carbons. So let's see one let me do this in another color. So we have one, two three, four, five six carbons. So one, two, three, four, five, six carbons. And then all the other bonds are with hydrogens. So let me draw this as well as I can. Carbon at least typically forms four bonds... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
So one, two, three, four, five, six carbons. And then all the other bonds are with hydrogens. So let me draw this as well as I can. Carbon at least typically forms four bonds. So hydrogen hydrogen, hydrogen, hydrogen hydrogen, hydrogen, hydrogen hydrogen, this right over here is hexane. This thing has no polarity to it... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
Carbon at least typically forms four bonds. So hydrogen hydrogen, hydrogen, hydrogen hydrogen, hydrogen, hydrogen hydrogen, this right over here is hexane. This thing has no polarity to it. It doesn't form hydrogen bonds, it doesn't have any polarity. And so if you were to take hexane and throw it into water, it's not ... | Water as a solvent Water, acids, and bases Biology Khan Academy.mp3 |
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