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If the substrate is able to get there first, then the inhibitor isn't able to bind, and the reaction does get catalyzed. Now, the inhibitor and the substrate, they both might compete for the active site, if we're talking about competitive inhibition. But you also have allosteric competitive inhibition, where they're st... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
Whoever gets there first gets the enzyme, but the inhibitor doesn't necessarily bind at the active site. They bind at an allosteric site, but it's the same idea. If the inhibitor gets to the allosteric site before the substrate gets to the active site, then the conformation of the protein changes so that the active sit... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
Something like, let me draw in that same color. It changes, the conformation of the protein changes a little bit, and then the actual intended substrate isn't able to bind. If the intended substrate binds, then that changes the conformation a little bit at the allosteric site, and then the inhibitor isn't able to bind.... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So if that's competitive inhibition, where there's like, who gets to the enzyme first, what is non-competitive inhibition all about? Well, let's draw that. So non-competitive inhibition. So non-competitive, competitive inhibition. And the big picture here is that they can both bind. Whether one binds to the enzyme does... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So non-competitive, competitive inhibition. And the big picture here is that they can both bind. Whether one binds to the enzyme doesn't affect whether the other binds. So let's talk about it a little bit. So this is my enzyme. That's my enzyme right over there. And what we have happening, of course, is if the substrat... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So let's talk about it a little bit. So this is my enzyme. That's my enzyme right over there. And what we have happening, of course, is if the substrate's able to get to the active site, then of course the reaction is going to be catalyzed. And we saw that up here. Substrate binds to the active site, and then the react... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
And what we have happening, of course, is if the substrate's able to get to the active site, then of course the reaction is going to be catalyzed. And we saw that up here. Substrate binds to the active site, and then the reaction is catalyzed. In this case, the substrate got broken up into two other molecules. But in n... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
In this case, the substrate got broken up into two other molecules. But in non-competitive inhibition, what happens is the substrate can bind, and so can an inhibitor. And so can an inhibitor. And the inhibitor can bind in an allosteric site. So this is our inhibitor right over here. The inhibitor can bind at an allost... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
And the inhibitor can bind in an allosteric site. So this is our inhibitor right over here. The inhibitor can bind at an allosteric site. And when they're both bound, notice they're not competing for the enzyme. They both can be on the enzyme. This character can bind to the enzyme whether or not the substrate is there.... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
And when they're both bound, notice they're not competing for the enzyme. They both can be on the enzyme. This character can bind to the enzyme whether or not the substrate is there. But if this guy binds to the enzyme, the substrate can still bind to the enzyme, but now the reaction isn't going to proceed. So now the ... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
But if this guy binds to the enzyme, the substrate can still bind to the enzyme, but now the reaction isn't going to proceed. So now the reaction is going to look like this. So let me, so now there's not going to be any reaction. If this happens, the only option is is that they both unbind. So now this character is jus... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
If this happens, the only option is is that they both unbind. So now this character is just going to leave the active site. No reaction, no reaction has been catalyzed. So it just prevented anything from happening. And maybe this guy, this guy leaves as well. And the way I showed this non-competitive inhibition, I show... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So it just prevented anything from happening. And maybe this guy, this guy leaves as well. And the way I showed this non-competitive inhibition, I showed it happening at an allosteric site. The inhibitor attaching at an allosteric site. But it actually doesn't even have to be the same case as long as it does not preven... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
The inhibitor attaching at an allosteric site. But it actually doesn't even have to be the same case as long as it does not prevent the, as long as it can actually bind close to or even at the active site, as long as it does not prevent the substrate from binding to the active site. So you can even have a situation lik... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So you can even have a situation like this. This is the one that's typically given for non-competitive inhibition where you have the inhibitor binding at an allosteric site. But the idea here is that they're not competing. Both of them can bind to the enzyme. If one of them binds first, then the other one can still bin... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
Both of them can bind to the enzyme. If one of them binds first, then the other one can still bind. If the substrate binds first, then the inhibitor can still bind. If the inhibitor binds first, then the substrate can still bind. But the reaction is not going to be catalyzed. But you can even have a situation, you can ... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
If the inhibitor binds first, then the substrate can still bind. But the reaction is not going to be catalyzed. But you can even have a situation, you can even have a situation where the inhibitor and the substrate can both bind in or around the active site. So that's the inhibitor, and then this is our substrate. This... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
So that's the inhibitor, and then this is our substrate. This is the substrate. But once again, this reaction is not going to occur. We have non-competitive inhibition. They're not competing for the thing. They can both bind to it. Whether they can bind isn't dependent on whether the other one is bound. | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
We have non-competitive inhibition. They're not competing for the thing. They can both bind to it. Whether they can bind isn't dependent on whether the other one is bound. But if the inhibitor is there, then it's not going to allow the reaction to actually be catalyzed, as opposed to competitive inhibition. Whoever get... | Noncompetitive inhibition Energy and enzymes Biology Khan Academy.mp3 |
But then you could keep going, and you could form longer chains of glucose molecules. And these things, where you take a monosaccharide, glucose is the most common example of that, and you create chains of these, we call these polysaccharides. Polysaccharides. This is a polysaccharide. And there's all sorts of interest... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
This is a polysaccharide. And there's all sorts of interesting examples of polysaccharides all around you, especially polysaccharides of glucose, or things that are derived from glucose. This right here, this is a bowl of mashed potatoes, which is mostly starch, which is mainly just chains of glucose. So this right ove... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So this right over here, let me do that in a color that's actually visible. So that is starch. That is starch. The shell of a lot of insects, and things like lobsters, and the wings of these insects right over here, that's made of something called chitin. And chitin is also a polysaccharide. It's made of chains of, ess... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
The shell of a lot of insects, and things like lobsters, and the wings of these insects right over here, that's made of something called chitin. And chitin is also a polysaccharide. It's made of chains of, essentially a modification of glucose, chains of that. That's chitin right over there. Very similar to starch in o... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
That's chitin right over there. Very similar to starch in our muscles, we have glycogen, which is our store of energy, in our muscles. You have cellulose, which is actually probably all around you right now. Cellulose are things like, let me write this down, because this is something that is all around you, and you don... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
Cellulose are things like, let me write this down, because this is something that is all around you, and you don't even realize it. Cellulose, this is what constitutes things like paper, and wood. It's involved in the cell walls of plants. This right over here is a picture of cotton, cotton in its natural form. And cot... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
This right over here is a picture of cotton, cotton in its natural form. And cotton is actually one of the purest forms of cellulose. It's roughly 90% cellulose. And if you take a zoom in on a cotton fiber, or actually a fiber of cellulose, you will see chains of glucose molecules. So you see this right over here, that... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And if you take a zoom in on a cotton fiber, or actually a fiber of cellulose, you will see chains of glucose molecules. So you see this right over here, that is a glucose molecule. Then you see another glucose molecule, and this chain has been formed through dehydration synthesis. And the difference between starch and... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And the difference between starch and cellulose, or the main difference in terms of how this bonding has, with starch, the glucose molecules just keep forming the way that you saw in the video in dehydration synthesis, while in cellulose, they get flipped over. So you can see here, this oxygen is pointing that way, thi... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
What gives it its structure are these hydrogen bonds that form between the partially negative, very electronegative oxygens on one strand, and the partially positive hydrogens on another strand. And that's actually what give its structure. So really, really interesting things, these polysaccharides. But a question is, ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
But a question is, how do you actually break these things down? If I were to eat these mashed potatoes, how do I eventually turn this thing into glucose so I can use it for energy? And the way that that happens, is through hydrolysis. And you can break down this word, the hydro, this is, if you see hydro, the prefix hy... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And you can break down this word, the hydro, this is, if you see hydro, the prefix hydro, that's a good clue that it has something to do with water. And then if you see lysis, if you're lysing something, this means that you're gonna break it down. So this is breaking down something using water. And that's exactly what ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And that's exactly what happens with hydrolysis. If you have this polysaccharide, and let's say we, let's throw a water molecule in there, we are going to add up, this water molecule is going to be able to break, it's going to be able to break one of these bonds. So we might end up with something like, we would end up,... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
With, that looks something, that looks something like that. So half of this water molecule gets broken up essentially to break this bond. It's the opposite of dehydration synthesis. So let's see if we can understand, get an overview of exactly how that happens. So this right over here, this is a, this is a maltose, thi... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So let's see if we can understand, get an overview of exactly how that happens. So this right over here, this is a, this is a maltose, this is maltose right over here, it's disaccharide, it's just two glucose molecules attached to each other. If we kept doing this, if this kept going, if this guy had a bond to another ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
If this was flipped over in the chain and they kept flipping over and over, then we could be talking about cellulose. But let's just think about how this, the mechanism, the mechanism by which this bond can actually be broken. And it's really just the reverse of dehydration, the reverse of dehydration synthesis. So we ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So we can, this is just gonna be an overview of it. So we could start, this oxygen right over here, it's got two, it's got two lone pairs. There's always a chance that if it bumps into something in just the right way, it could nab, it could nab a hydrogen proton that is just sitting out there, that is just sitting out ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
We're assuming that this is happening in an aqueous solution. It's happening in water. So it could just grab a hydrogen proton from maybe a passing hydronium molecule. And so if it does that, it would form, it would form, it would form a covalent bond and have a positive charge. And now relative to actually both carbon... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And so if it does that, it would form, it would form, it would form a covalent bond and have a positive charge. And now relative to actually both carbons, but let's focus on this carbon right over here. This guy would be what we call in organic chemistry a good leaving group, a good leaving group. So these electrons, t... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So these electrons, these electrons, the oxygen might wanna just take these back because hey, it's got a positive charge, oxygen is really electronegative. And so if things just bump in exactly the right way, if things interact in exactly the right way, you might have another water molecule. And this is where that extr... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So let's say this is just another water molecule just passing by in exactly the right way. This could form, this could form a bond, this could form a bond with that carbon right over there. And just as it forms a bond with that carbon, the carbon says, okay, I'm getting to share some other electrons, let me let go of t... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So let's go of these electrons. And then what do you have left? Well, we can go over here. And so now this carbon has, let me color code it. So this bond that was just forming, that is this bond, that is this bond right over here. This oxygen, this oxygen is this oxygen right over there. It actually has another hydroge... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And so now this carbon has, let me color code it. So this bond that was just forming, that is this bond, that is this bond right over here. This oxygen, this oxygen is this oxygen right over there. It actually has another hydrogen attached to it, so let me do that. So right when it makes the bond, it'll have a positive... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
It actually has another hydrogen attached to it, so let me do that. So right when it makes the bond, it'll have a positive charge. And then this bond, this bond right over here goes back to this oxygen. This oxygen right over here is that oxygen right over there. Now, when it started off, this guy grabbed a, this guy, ... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
This oxygen right over here is that oxygen right over there. Now, when it started off, this guy grabbed a, this guy, well, and this guy, and this, let me, actually, and this hydrogen proton that it grabbed, I've shown in orange, that's this one. That's this one right over here. That's that one right over here. Now, thi... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
That's that one right over here. Now, this one grabbed a hydrogen proton, and now this one can actually give back a hydrogen proton to the solution. So if a water molecule passing by can just grab this hydrogen proton and then become a hydronium molecule. And so it took a hydrogen proton, it's giving it back. And so wh... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
And so it took a hydrogen proton, it's giving it back. And so what we are left with, but it took up this water molecule right over here to break the bond. And so this is a positive charge. It could be a passing hydronium molecule, and then it'll just hand it off to that. And there you have it. We have two standalone gl... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
It could be a passing hydronium molecule, and then it'll just hand it off to that. And there you have it. We have two standalone glucose molecules right over there. We have broken the bond. And these could be parts of chains, in which case we've just broken the chain. Or if we're just dealing with maltose, now we've br... | Hydrolysis Macromolecules Biology Khan Academy.mp3 |
So this right over here is a picture of the amoeba Chaos carolinensi. And what you see here is a projection coming off from the main part of the cell. And this is called a pseudopod, which is referring to it being a false foot. The pod is coming from the same root word as podiatry, which is referring to the foot. And w... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
The pod is coming from the same root word as podiatry, which is referring to the foot. And what I really want you to appreciate, this is used by amoeba either to move around or it could be even used to attack something that it wants to engulf. And think about what it might take to be able to do this, to be able to grow... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
You need all sorts of microstructures in here that will extend or contract as necessary. And think about the machinery that you need to do that. And so the key realization is sometimes we just imagine cells as these bags of fluid with a few things floating around. But they're these incredibly complex structures. And bi... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
But they're these incredibly complex structures. And biologists even today don't fully understand how everything works and they're studying how these things actually come to be. Now another structure that you will often see on unicellular organisms that either help them move around or even help move other things around... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
So this right over here is a picture of Oxytricha triflax, which is a unicellular organism. It's a eukaryote. And you can clearly see these projections from its body here, these hair-like structures. Remember, this is a unicellular organism. If we were to, it's actually a fairly, it's a decent-sized one, that would be ... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
Remember, this is a unicellular organism. If we were to, it's actually a fairly, it's a decent-sized one, that would be about, something like that would be about 30 micrometers right over there or 30 millionths of a meter or 30 thousandths of a millimeter. So small by our scale, but it's actually pretty big on the scal... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
And once again, these cilia tend to move in unison to either allow the microorganism to move around or sometimes they're used to move other things around. For example, the cells that line your lungs will have cilia that are used to move things up or down, to move some of the saliva or any particles that are in there. N... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
It can have two nuclei. And within the nucleus, its DNA can be extremely fragmented. Most organisms have a reasonable number of chromosomes. Human beings have 23 pair. That's actually a fairly large number. Oxytricha triflax could have thousands of chromosomes. And what's really interesting about Oxytricha triflax is h... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
Human beings have 23 pair. That's actually a fairly large number. Oxytricha triflax could have thousands of chromosomes. And what's really interesting about Oxytricha triflax is how it mates. When it is under stress, it will merge with another Oxytricha triflax. And instead of producing another offspring, they mingle t... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
And what's really interesting about Oxytricha triflax is how it mates. When it is under stress, it will merge with another Oxytricha triflax. And instead of producing another offspring, they mingle their DNA together. So by mating, they change each other's genetic makeup, which is fascinating. And depending on your per... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
So by mating, they change each other's genetic makeup, which is fascinating. And depending on your perspective, highly romantic. Now, another related idea is instead of having many cilia, some unicellular organisms will just have one large thing that looks like a tail that they can whip around to move. So this right ov... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
So this right over here is a commonly studied green algae. It's called Chlamydomonas. And you can see very clearly here, this flagellum, this tail-like structure. And this is extremely thin. We're seeing it under a very powerful microscope right over here. But just to get a sense of scale, a micrometer here would be ab... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
And this is extremely thin. We're seeing it under a very powerful microscope right over here. But just to get a sense of scale, a micrometer here would be about that. So the width of this flagellum, flagellum would be the singular. If we're talking about many of these, we would say flagella. This is about 1 1⁄4 of a mi... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
So the width of this flagellum, flagellum would be the singular. If we're talking about many of these, we would say flagella. This is about 1 1⁄4 of a micrometer. Another way of thinking about it, you could put 4,000 of these side by side, and you would have the width of a millimeter. So extremely, extremely small. But... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
Another way of thinking about it, you could put 4,000 of these side by side, and you would have the width of a millimeter. So extremely, extremely small. But once again, it really is amazing that these what seem like simple organisms to us are actually quite complex. There's a whole study of how these flagella move aro... | Introduction to cilia, flagella and pseudopodia Cells High school biology Khan Academy.mp3 |
And the phosphorylation of glucose is an example of that. And we go into some detail into that on the video on coupled reactions, and I think we actually call that the phosphorylation of glucose-6-phosphate. But it's super important because by putting the phosphate group on a glucose, it's ready to be the input to a wh... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
It allows the glucose to be tagged, so it's going to be hard for it to escape the cell again. And it's a fairly straightforward mechanism where you have a lone pair of electrons on this hydroxyl group right over here. And then it attempts to, if it's in the right configuration, it can form a bond with the phosphorus in... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
Now the reason why it doesn't happen on its own, even though it's energetically favorable, once you form the bond, you have electrons that are going to be able to go into a lower energy state. So it has a negative delta G. If this is the molecules before the reaction, this is how much free energy they have before the r... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
They have been able to release energy. So this is something that we would consider to be spontaneous. But for the reaction to happen, you need a little bit of energy to be put into the system. We call this our activation energy. And you might say, well, why is that? Well, we have electrons that want to form a bond with... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
We call this our activation energy. And you might say, well, why is that? Well, we have electrons that want to form a bond with this phosphorus, but this phosphorus is surrounded by negative charges. This oxygen right over here has a negative charge. This oxygen right over here has a negative charge. And as you can ima... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
This oxygen right over here has a negative charge. This oxygen right over here has a negative charge. And as you can imagine, electrons don't like being around other electrons, like charges repel each other. So in order for this reaction to occur, or for it to occur more frequently, it has to be catalyzed. A catalyst i... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
So in order for this reaction to occur, or for it to occur more frequently, it has to be catalyzed. A catalyst is anything that makes a reaction happen faster, or even allows the reaction to happen at all. And when we talk about catalysts in biological systems, we're typically talking about enzymes. Enzymes. And the wa... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
Enzymes. And the way that an enzyme might catalyze this reaction, we actually talk about it when we talk about coupled reactions, is well, maybe it can provide some positive charges. It can provide some positive charges around these negative charges to pull them further away, to create space, so that you can actually h... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so what an enzyme would do, it would make this curve, instead of having this hump on it, the curve would look more like this, so that the reaction can just proceed. But what are these enzymes? These things that can, you know, maybe it could place some interesting charge that can allow the reaction to happen a certa... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
It might bend the molecules in a certain way to expose some bonds. It might have a more acidic or basic environment that might be more favorable for the reaction. What are these seemingly magical things? Well, at a very high level, they tend to be these protein complexes, plus or minus a few other things. So you can vi... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
Well, at a very high level, they tend to be these protein complexes, plus or minus a few other things. So you can view them as proteins, and you know, maybe sometimes there'll be multiple polypeptide chains put together. They might have some other ions associated with them. But for the most part, they are proteins. And... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
But for the most part, they are proteins. And the molecules that are going to react, that are going to bind to the proteins, we call these the substrates. So these, in this reaction right here, the glucose and the ATP, these are going to be the substrates. So you can imagine, you can imagine the enzyme that does this, ... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
So you can imagine, you can imagine the enzyme that does this, and the general term for the enzyme that helps phosphorylate a sugar molecule like this, we call it a hexokinase. So it might be this crazy-looking protein. We're going to take better looks at this in a few moments. But the ATP, the ATP might bind to it rig... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
But the ATP, the ATP might bind to it right over there. ATP is one of the substrates. And then the glucose might bind to it right over there. And so the two substrates bind, and the area where all of this is going on, we call that the active site. So the active site, because that's where all the action is. The active s... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so the two substrates bind, and the area where all of this is going on, we call that the active site. So the active site, because that's where all the action is. The active site. And often when you have the substrates bind, they are able to interact with the protein to make the fit even stronger, to make it even mo... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And often when you have the substrates bind, they are able to interact with the protein to make the fit even stronger, to make it even more suitable for the reaction to take place. And so the whole protein might bend a little bit to kind of lock these two in place a little bit more, and we call that induced fit. Induce... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so where would these positive charges come from? Well, these would be things that are the side chains of the different amino acids on the polypeptide chain, on the protein. And it could even be other ions that get involved. In fact, in particular, to facilitate the phosphorylation of glucose, a magnesium ion might ... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
In fact, in particular, to facilitate the phosphorylation of glucose, a magnesium ion might be involved to help draw some positive charge away. But there's other positively charged groups that help draw a charge away so that the reaction is more likely to occur. So that's what enzymes are. And they tend to be optimally... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And they tend to be optimally working in certain pH environments or at certain temperatures. In general, higher temperatures allow more interactions, things are bumping around more. But if temperatures get a little bit too high, the protein or the enzyme might stop working. It might denature. It might lose its actual s... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
It might denature. It might lose its actual structure. And what I want to now give you an appreciation for is how beautiful and complex these structures are. And you should appreciate what I'm showing you. These are in your cells. These are in your, you know, look at your hand. Look at, you know, everything around you. | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And you should appreciate what I'm showing you. These are in your cells. These are in your, you know, look at your hand. Look at, you know, everything around you. There's a lot of this stuff going on inside of you. So hopefully it gives an appreciation for the complexity of you as a biological system, but frankly, all ... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
Look at, you know, everything around you. There's a lot of this stuff going on inside of you. So hopefully it gives an appreciation for the complexity of you as a biological system, but frankly, all biological systems. So this right over here, this is a visualization of a hexokinase, one variety of it. And just to get ... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
So this right over here, this is a visualization of a hexokinase, one variety of it. And just to get a sense of scale, this is a glucose molecule. And this right over here is an ATP. And so they will bind. These are the two substrates. They will bind at the active site. You might have the induced fit where this fits ar... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so they will bind. These are the two substrates. They will bind at the active site. You might have the induced fit where this fits around it. It draws some charge away. It might bend the molecules in a certain way so that they're more likely to interact, bring these things close together. And so you're going to hav... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
You might have the induced fit where this fits around it. It draws some charge away. It might bend the molecules in a certain way so that they're more likely to interact, bring these things close together. And so you're going to have the reaction occur. And then once the reaction occurs, they're not going to want to bi... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so you're going to have the reaction occur. And then once the reaction occurs, they're not going to want to bind to the substrates anymore. I guess you could say the products at that point. And then they're going to let go of them. And then the enzyme hasn't changed. And that's an important property of an enzyme. I... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And then they're going to let go of them. And then the enzyme hasn't changed. And that's an important property of an enzyme. It's not like it just has one use and it goes away. It can keep doing this over and over and over again. One enzyme will do this many, many, many, many, many times in its actual life. And so now ... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
It's not like it just has one use and it goes away. It can keep doing this over and over and over again. One enzyme will do this many, many, many, many, many times in its actual life. And so now what I want to show you is a little three-dimensional visualization that I got from a website. So let me go get that. I'll go... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And so now what I want to show you is a little three-dimensional visualization that I got from a website. So let me go get that. I'll go ahead and pause my recording so I could get this little simulation or this model. And this is actually a hexokinase as well. And hexokinases come in a bunch of different varieties. Bu... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And this is actually a hexokinase as well. And hexokinases come in a bunch of different varieties. But this is a pretty neat thing to look at. And this has been visualized differently. When you look up protein images on the web or anywhere, you'll see them sometimes with these ball and stick models. Sometimes you'll se... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And this has been visualized differently. When you look up protein images on the web or anywhere, you'll see them sometimes with these ball and stick models. Sometimes you'll see them in these space-filling models. Sometimes you'll see them with this kind of, where you see the various structures. You notice the alpha h... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
Sometimes you'll see them with this kind of, where you see the various structures. You notice the alpha helices here that we studied when we talked about protein structures. And you can also see some beta sheets. But this gives you an appreciation of the binding sites and how these things might interact. This right ove... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
But this gives you an appreciation of the binding sites and how these things might interact. This right over here, that is a molecule of ATP. And then right next to it, I believe, if I'm looking at that right, that is a molecule of glucose. And notice they have bound, they are the two substrates, they have bound at the... | Enzymes Energy and enzymes Biology Khan Academy.mp3 |
And at a very high level, the endomembrane system is all of the membranes that interact with each other inside of a cell. So what membranes are we talking about? Well, you can start off by talking about the cell membrane itself. And all of these membranes, these have bilayers of phospholipids. Sometimes my brain malfun... | Endomembrane system Structure of a cell Biology Khan Academy.mp3 |
And all of these membranes, these have bilayers of phospholipids. Sometimes my brain malfunctions and I call them bilipid layers. But these are bilayers of phospholipids. So if I were to zoom in right over here, if I were to zoom in right over there, that line, it really is a bilayer, a bilayer of phospholipids. So it ... | Endomembrane system Structure of a cell Biology Khan Academy.mp3 |
So if I were to zoom in right over here, if I were to zoom in right over there, that line, it really is a bilayer, a bilayer of phospholipids. So it would look like this. So you have your hydrophilic heads pointing outwards and your hydrophobic tails pointing inwards. So hydrophilic heads pointing outwards, hydrophobic... | Endomembrane system Structure of a cell Biology Khan Academy.mp3 |
So hydrophilic heads pointing outwards, hydrophobic tails pointing inwards, and it keeps going. So you have, if we think of it from left to right, you have a layer of two, or you have a bilayer, I should say, of phospholipids. That's going to be true of the cellular membrane. That's going to be true of the outer nuclea... | Endomembrane system Structure of a cell Biology Khan Academy.mp3 |
That's going to be true of the outer nuclear membrane. Right over here, we drew this one on the video on the endoplasmic reticulum. And so over here, you see these two membranes. You might say, okay, is this a bilayer? No, this is actually two bilayers. So this membrane right over here has a phospholipid bilayer, and t... | Endomembrane system Structure of a cell Biology Khan Academy.mp3 |
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