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Well, here we have a colorblind female. She has two of the recessive alleles, so that female will be colorblind. This is a female carrier, but they will not show the phenotype of being colorblind. This over here is a colorblind male, has only one X chromosome, and it has the colorblind allele on it. And this is a non-c... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
And NADH is the main character here, but there are other coenzymes that are involved, like coenzyme Q, and you see that right over here. And what I want to talk about in this video is the process by which we actually are able to produce ATP from the oxidation of these coenzymes. And that process is what we call oxidati... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Oxidative, oxidative phosphorylation. Now the main player when we're talking about cellular respiration and oxidative phosphorylation is NADH. NADH in the process of being oxidized to NAD, so it gets oxidized to N, gets oxidized to NAD, which has a positive charge, I often call it NAD+, but let's think about what this ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
If we just look at, if we just look at this reaction from the point of view of NADH being oxidized, remember, oxidation is losing electrons. So NAD+, and then you're gonna have plus a hydrogen proton, plus you're going to have two electrons, plus two electrons. So this is what's happening when NADH is being oxidized in... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So this is oxidation right over here. Let me do this in another color. So this is oxidation. And this process of oxidation, if these electrons get the appropriate acceptor molecule, it can release a lot of energy. And the eventual acceptor of those electrons, and I can show the corresponding reduction reaction, is we h... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And this process of oxidation, if these electrons get the appropriate acceptor molecule, it can release a lot of energy. And the eventual acceptor of those electrons, and I can show the corresponding reduction reaction, is we have two electrons, two electrons, plus two hydrogen protons, or really just two protons. A hy... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
It doesn't have a neutron for the main isotope of hydrogen. So two protons plus half of an oxygen molecule, yielding, you put all of these three, all of these things together, I should say, and you are going to get a water molecule. So you can think of it as the oxygen being the final acceptor of the electrons. And oxy... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And oxygen likes to oxidize things. That's where the whole word oxidation comes from. So here, or another way to think of it, oxygen likes to be reduced. It likes to hog electrons. So this is oxygen is being reduced. Oxygen, oxygen reduced. So if you just directly transferred these electrons from our NADH to the oxygen... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
It likes to hog electrons. So this is oxygen is being reduced. Oxygen, oxygen reduced. So if you just directly transferred these electrons from our NADH to the oxygen, it would release a lot of energy, but it would release so much energy that you wouldn't be able to capture most of it. You wouldn't be able to use it to... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So if you just directly transferred these electrons from our NADH to the oxygen, it would release a lot of energy, but it would release so much energy that you wouldn't be able to capture most of it. You wouldn't be able to use it to actually do useful work. And so the process of oxidative phosphorylation is all about ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And we do it by transferring these electrons from one electron acceptor to another electron acceptor. And every time we do that, we release some energy. And then that energy can be, in a more controlled way, be used to actually do work. And in this case, that work is pumping hydrogen protons across a membrane, and then... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And in this case, that work is pumping hydrogen protons across a membrane, and then that gradient that forms can actually be used to generate ATP. So let's talk through it a little bit more. So we're gonna go, these electrons, they're gonna be transferred, and I won't go into all of the details. This is to just give yo... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This is to just give you a high-level overview of it. They're going to be transferred to different acceptors, which then transfer it to another acceptor. So it might go to a coenzyme, coenzyme Q, and a cytochrome, cytochrome C, and it keeps going to different things, eventually, eventually getting to this state right o... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And in the process, every step of the way, energy is being released. Energy, energy is being released. And this energy, as we will see in a second, is being used to pump hydrogen protons across a membrane. And we're gonna use that gradient to actually drive the production of ATP. So let's think about that a little bit ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And we're gonna use that gradient to actually drive the production of ATP. So let's think about that a little bit more. So let's zoom in on a mitochondria. So this is mitochondria. Let's say that's our mitochondria. And let me draw the inner membrane. And then these folds in the inner membrane, the singular for them is... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So this is mitochondria. Let's say that's our mitochondria. And let me draw the inner membrane. And then these folds in the inner membrane, the singular for them is crista. If we're talking about pearl, it's cristae. So we have these folds in the inner membrane right over here. So just to be clear what's going on, this... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And then these folds in the inner membrane, the singular for them is crista. If we're talking about pearl, it's cristae. So we have these folds in the inner membrane right over here. So just to be clear what's going on, this is the outer membrane, outer membrane. That is the inner membrane, inner membrane. The space be... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So just to be clear what's going on, this is the outer membrane, outer membrane. That is the inner membrane, inner membrane. The space between the outer and the inner membrane, the space right over here, that is the intermembrane space. Intermembrane, membrane space. And then the space inside the inner membrane, let me... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Intermembrane, membrane space. And then the space inside the inner membrane, let me make sure you can read that space properly, this space over here, this is the matrix. This is the matrix. And that is the location of our citric acid cycle or our Krebs cycle. And I can symbolize that with this little cycle. You know, w... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And that is the location of our citric acid cycle or our Krebs cycle. And I can symbolize that with this little cycle. You know, we have a cycle going on here. And so that's where the bulk of the NADH is being produced. Now we also talk about some other coenzymes. In some books or classes you might hear about FAD being... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And so that's where the bulk of the NADH is being produced. Now we also talk about some other coenzymes. In some books or classes you might hear about FAD being reduced to FADH2, which can then be oxidized as part of oxidative phosphorylation. Other times people say, well, actually that's going to be attached to an enz... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Other times people say, well, actually that's going to be attached to an enzyme. And then that FADH2 is used to reduce coenzyme Q to produce QH2, and then that participates in oxidative phosphorylation. So you could think about either one of these. I'll focus on QH2. Well, we'll actually focus on NADH because it's all ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
I'll focus on QH2. Well, we'll actually focus on NADH because it's all a similar process. FADH2 or QH2 enters a little bit later down this process, so they don't produce as much energy, but they still can be used to help produce ATP. But anyway, our citric acid cycle, which we have shown in previous videos, that occurr... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
But anyway, our citric acid cycle, which we have shown in previous videos, that occurring in the matrix, and now let me do a little zoom in here. Let me do a zoom in. So if I were to zoom in, let's say, let me just get a color that we can see. So if I were to zoom in right over there, let's show this fold in the inner ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So if I were to zoom in right over there, let's show this fold in the inner membrane, and let's make it clear that this is, like all of these membranes, these are all phospholipid bilayers. So let me draw, let me do the same color that I did in the actual diagram. So we have all these, we have a bilayer of phospholipid... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So, almost done. All right, just to make it clear. And you have these enzymes that go across the phospholipid bilayer, and these enzymes are, these protein complexes are actually what facilitate oxidative phosphorylation, and this chain of enzymes, this chain of proteins, is what we call the electron, or is what we cal... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So let me draw that. So maybe this is one protein, and I'm just drawing them as kind of these abstract, abstract, and you could refer to the electron transport chain as either these proteins, or you could use this process of these electrons going from one acceptor to another, eventually making its way all the way to th... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This is another protein right over here. And I'll just do a couple of them. This is really about a high-level overview. And what's happening, what's happening is as the, and this is just gonna be a very high-level simplification of it, as you have your, let's say initially, your NADH comes in, so your NADH comes in, an... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And what's happening, what's happening is as the, and this is just gonna be a very high-level simplification of it, as you have your, let's say initially, your NADH comes in, so your NADH comes in, and it donates the protons and the electrons, and then it becomes NAD+, so it just became oxidized. Those electrons will g... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This is where our citric acid cycle occurs. So we have protons being pumped out. So we have these protons being pumped out as we release energy, as we go from one electron acceptor to another electron acceptor. And so the electrons are going from higher energy states, and they're releasing energy as they go down this k... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And so the electrons are going from higher energy states, and they're releasing energy as they go down this kind of, towards more and more electronegative things, and they feel more comfortable with the water than they felt with the NADH, and by doing so, by these electrons going down that gradient, I guess you could s... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Now, this is stored energy because this is an electrochemical gradient. All this positive charge, they wanna get away from each other. They wanna go to this less positive matrix right over here. And also, just you have a higher concentration of hydrogens and just natural diffusion. They would wanna go down their concen... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And also, just you have a higher concentration of hydrogens and just natural diffusion. They would wanna go down their concentration gradient into the matrix. There's less of the protons here. There's less of the protons in the matrix than there are in the intermembrane space. And so, that's the opportunity to now take... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
There's less of the protons in the matrix than there are in the intermembrane space. And so, that's the opportunity to now take that energy and produce ATP with them. And the way that this happens, the way this happens, let me extend my membrane a little bit. That's a different color. So let me extend my membrane a lit... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
That's a different color. So let me extend my membrane a little bit, is using a protein called ATP synthase. It's actually a protein complex, I should say. So ATP synthase, really an enzyme. And ATP synthase goes across, it's actually a fascinating molecule. I'll show a better diagram of it in a second. But your ATP sy... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So ATP synthase, really an enzyme. And ATP synthase goes across, it's actually a fascinating molecule. I'll show a better diagram of it in a second. But your ATP synthase goes across the membrane. It actually has a fairly mechanical structure where it has a bit of a housing and it has an axle in the housing. So it look... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
But your ATP synthase goes across the membrane. It actually has a fairly mechanical structure where it has a bit of a housing and it has an axle in the housing. So it looks maybe something like this. And it actually has something, you can view this as a thing that maybe holds it together. So it's going across the membr... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And it actually has something, you can view this as a thing that maybe holds it together. So it's going across the membrane. I'll show a better diagram of it in a second. So then of course the membrane continues on. Membrane continues on. And what happens is, it allows these hydrogen protons to flow down their electroc... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So then of course the membrane continues on. Membrane continues on. And what happens is, it allows these hydrogen protons to flow down their electrochemical gradient. So these hydrogen protons go down and they actually cause the axle to spin. So maybe I'll draw it this way. They actually cause the axle to spin as they ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So these hydrogen protons go down and they actually cause the axle to spin. So maybe I'll draw it this way. They actually cause the axle to spin as they go down their electrochemical gradient. And as this axle spins, and this axle, it's not this smooth, it's not like it's made out of metal or something. It's made out o... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And as this axle spins, and this axle, it's not this smooth, it's not like it's made out of metal or something. It's made out of amino acids. So it's all bumpy and all the rest. So it looks something like this. And what happens is you have ADPs, you have ADPs that get lodged in here. So let's say that's an ADP. And the... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So it looks something like this. And what happens is you have ADPs, you have ADPs that get lodged in here. So let's say that's an ADP. And then a phosphate group. And there are actually three different sites where this can happen. So that's an ADP and a phosphate group. And there's another site that I'm not drawing. | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And then a phosphate group. And there are actually three different sites where this can happen. So that's an ADP and a phosphate group. And there's another site that I'm not drawing. But as this thing rotates, it essentially keeps changing the conformation of the protein and jams the phosphate group into the ADP, which... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And there's another site that I'm not drawing. But as this thing rotates, it essentially keeps changing the conformation of the protein and jams the phosphate group into the ADP, which takes energy and locks them into place to form the ATP. And when they form the ATP, they no longer attach to the active site and they l... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So you have this, actually this mechanical motor. You can view it as almost like a turbine, a water turbine. The water goes through it and that energy is used to generate electricity. Here, hydrogen protons go down their electrochemical gradient. That rotary motion is then used to jam phosphate groups onto ADPs to form... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Here, hydrogen protons go down their electrochemical gradient. That rotary motion is then used to jam phosphate groups onto ADPs to form ATPs. And so this is the actual ATP production going on. And to get a better appreciation for what's going on, this is going on in your body right now. This is going on in my body. Ot... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
And to get a better appreciation for what's going on, this is going on in your body right now. This is going on in my body. Otherwise, I wouldn't be able to talk. This is how I'm generating my energy. This is a more accurate depiction of ATP synthase right over here. And based on this diagram, this is our, this, let me... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This is how I'm generating my energy. This is a more accurate depiction of ATP synthase right over here. And based on this diagram, this is our, this, let me make sure I'm, so this right over here, I'm having trouble, I'm having trouble drawing on this. Let me see if I can. So this part right over here, this area right... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Let me see if I can. So this part right over here, this area right over there, that's our intermembrane space. This right over here is our, this over here is our matrix. This membrane, this is a phospholipid bilayer. So if I wanted, I could draw the bilayer of phospholipids right over here. And this is our inner membra... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This membrane, this is a phospholipid bilayer. So if I wanted, I could draw the bilayer of phospholipids right over here. And this is our inner membrane, or we could say this is a fold in the inner membrane. This could be on our crista. And so the hydrogen protons, they build up in the intermembrane space because of th... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
This could be on our crista. And so the hydrogen protons, they build up in the intermembrane space because of the electron transport chain. And then they flow down, and then they flow down their electrochemical gradient, turn this rotor, and then they cause the creation of the ATPs over here. So you have ADP, ADP plus ... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
So you have ADP, ADP plus a phosphate group, and then you produce, and you produce your ATP. So this is fascinating. This is going on in the cells of your body. It's going on as you speak. It's not some abstract thing that is somehow separate from your reality. This is what is making your reality possible. So hopefully... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
It's going on as you speak. It's not some abstract thing that is somehow separate from your reality. This is what is making your reality possible. So hopefully you get a nice appreciation for this. I mean, we spent a lot of time talking about cellular respiration. We spent a lot of time talking about, okay, we can prod... | Oxidative phosphorylation and the electron transport chain Khan Academy.mp3 |
Frankly, if this process didn't occur, we probably wouldn't have life on Earth and I wouldn't be making this video for you because there would be no place for me to actually get food. And the process is called photosynthesis. And you're probably reasonably familiar with the idea. The whole idea is plants and actually b... | Photosynthesis.mp3 |
The whole idea is plants and actually bacteria and algae and other things. But we normally associate it with plants. Let me make it in very simple terms. So we normally associate it with plants. And it's the process that plants use, and you might have learned this when we were very young. It's the process that plants u... | Photosynthesis.mp3 |
So we normally associate it with plants. And it's the process that plants use, and you might have learned this when we were very young. It's the process that plants use to take carbon dioxide plus some water plus some, I'll do it in yellow, plus some sunlight and turn it into some sugars or some maybe carbohydrates or ... | Photosynthesis.mp3 |
And obviously this has two very profound pieces to it for us as a living species. One, we need carbohydrates or we need sugars in order to fuel our bodies. You saw that in the cellular respiration videos. We generate all of our ATP by performing cellular respiration on glucose, which is essentially a byproduct or a bro... | Photosynthesis.mp3 |
We generate all of our ATP by performing cellular respiration on glucose, which is essentially a byproduct or a broken down carbohydrate. It's the simplest one for us to process in cellular respiration. And then the second hugely important part is getting the oxygen. Once again, we need to breathe oxygen in order for u... | Photosynthesis.mp3 |
Once again, we need to breathe oxygen in order for us to break down glucose, in order to respire, in order to perform cellular respiration. So these two things are key for life, especially for life that breathes oxygen. So this process, other than the fact that it's interesting, that there are organisms around us, most... | Photosynthesis.mp3 |
You have these fusion reactions in the sun 93 million miles away, and it's releasing these photons, and some small subset of those photons reach the surface of Earth. They make their way through clouds and whatever else. And then these plants and bacteria and algae are able to harness that somehow and turn them into su... | Photosynthesis.mp3 |
We can then use that for energy, not that the cow is all carbohydrates, but this is essentially what is used as the fuel or the energy for all of the other important compounds that we eat. This is where we get all of our fuel. So this is fuel for animals. Or if you eat a potato directly, you're directly getting your ca... | Photosynthesis.mp3 |
Or if you eat a potato directly, you're directly getting your carbohydrates. But anyway, this is a very simple notion of photosynthesis, but it's not incorrect. If you had to know one thing about photosynthesis, this would be it. But let's delve a little bit deeper and try to get into the guts of it and see if we can u... | Photosynthesis.mp3 |
But let's delve a little bit deeper and try to get into the guts of it and see if we can understand a little bit better how this actually happens. I find it amazing that somehow photons of sunlight are used to create these sugar molecules or these carbohydrates. So let's delve a little bit deeper. In general, we can wr... | Photosynthesis.mp3 |
In general, we can write the general equation for photosynthesis. I've almost written it here, but I'll write it a little bit more scientifically specific. You start off with some carbon dioxide. You add to that some water. And you add to that, instead of sunlight, I'm going to say photons. Because these are what reall... | Photosynthesis.mp3 |
You add to that some water. And you add to that, instead of sunlight, I'm going to say photons. Because these are what really do excite the electrons in the chlorophyll that go down, and you'll see this process probably in this video, and we'll go in more detail in the next few videos. But that excited electron goes to... | Photosynthesis.mp3 |
But that excited electron goes to a high energy state, and as it goes to a lower energy state, we're able to harness that energy to produce ATPs, and you'll see NADPHs, and those are used to produce carbohydrates, but we'll see that in a little bit. But the overview of photosynthesis, you start off with these constitue... | Photosynthesis.mp3 |
So the general way we can write a carbohydrate is CH2O, and we'll put an N over here, that we could have N multiples of these. And normally your N will be at least 3. In the case of glucose, N is 6. You have 6 carbons, 12 hydrogens, and 6 oxygens. So this is a general term for a carbohydrate, but you could have many mu... | Photosynthesis.mp3 |
You have 6 carbons, 12 hydrogens, and 6 oxygens. So this is a general term for a carbohydrate, but you could have many multiples of that. You could have these long-chain carbohydrates. So you end up with a carbohydrate, and then you end up with some oxygen. So this right here isn't so different than what I wrote up her... | Photosynthesis.mp3 |
So you end up with a carbohydrate, and then you end up with some oxygen. So this right here isn't so different than what I wrote up here in my first overview of how we always imagined photosynthesis in our heads. In order to make this equation balance, let's say I have N carbons here, so I need N carbons there. Let's s... | Photosynthesis.mp3 |
Let's see, I have 2N hydrogens here, right? 2 hydrogens, and I have N there, so I need 2N hydrogens here. So I'll put an N out there, and let's see how many oxygens. I have 2N oxygens plus another N, so I have 3N oxygens. Let's see, I have 1N, and let's see, put an N here, and then I have 2N, and I think this equation ... | Photosynthesis.mp3 |
I have 2N oxygens plus another N, so I have 3N oxygens. Let's see, I have 1N, and let's see, put an N here, and then I have 2N, and I think this equation balances out. So this is a 30,000-foot view of what's going on in photosynthesis. But when you dig a little deeper, you'll see that this doesn't happen directly, that... | Photosynthesis.mp3 |
But when you dig a little deeper, you'll see that this doesn't happen directly, that this happens through a bunch of steps that eventually gets us to the carbohydrate. So in general, we can break down photosynthesis. I'll rewrite the word. We can break down photosynthesis. And we'll delve deeper into future videos, but... | Photosynthesis.mp3 |
We can break down photosynthesis. And we'll delve deeper into future videos, but I want to give you the overview first into 2 stages. We can call 1 the light reactions, or sometimes they're called the light-dependent reactions, and that actually would probably be a better way to write it. Let me write it like that. Lig... | Photosynthesis.mp3 |
Let me write it like that. Light-dependent means that they need light to occur. Light-dependent reactions. And then you have something called the dark reactions, and that's actually a bad name because it also occurs in the light. Dark reactions. I wrote it in a slightly darker color. And the reason why I said it's a ba... | Photosynthesis.mp3 |
And then you have something called the dark reactions, and that's actually a bad name because it also occurs in the light. Dark reactions. I wrote it in a slightly darker color. And the reason why I said it's a bad name is because it still occurs in the light. But the reason why they probably called it the dark reactio... | Photosynthesis.mp3 |
And the reason why I said it's a bad name is because it still occurs in the light. But the reason why they probably called it the dark reaction is that you don't need light, or that part of photosynthesis isn't dependent on photons to occur. So a better term for it would have been light-independent reaction. So just to... | Photosynthesis.mp3 |
So just to be clear, the light reactions actually need sunlight. They actually need photons for them to proceed. The dark reactions do not need photons for them to happen, although they do occur when the sun is out. They don't need those photons, but they need the byproducts from the light reaction to occur. So that's ... | Photosynthesis.mp3 |
They don't need those photons, but they need the byproducts from the light reaction to occur. So that's why it's called the light-independent reaction. They occur while the sun is out, but they don't need the sun. This needs the sun, so let me make it very clear. So this requires sunlight. This requires photons. And le... | Photosynthesis.mp3 |
This needs the sun, so let me make it very clear. So this requires sunlight. This requires photons. And let me just make a very brief overview of this. This will maybe let us start building a scaffold from which we can dig deeper. So the light reactions need photons, and then it needs water. So water goes into the ligh... | Photosynthesis.mp3 |
And let me just make a very brief overview of this. This will maybe let us start building a scaffold from which we can dig deeper. So the light reactions need photons, and then it needs water. So water goes into the light reactions, and out of the other side of the light reactions, we end up with some molecular oxygen.... | Photosynthesis.mp3 |
So water goes into the light reactions, and out of the other side of the light reactions, we end up with some molecular oxygen. So that's what happens in the light reactions, and I'm going to go much deeper on what actually occurs. And what the light reactions produce, it produces ATP, which we know is the cellular or ... | Photosynthesis.mp3 |
It produces ATP, and it produces NADPH. Now, when we studied cellular respiration, we saw the molecule NADH. NADPH is very similar. You just have this P there. You just have this phosphate group there. But they really perform similar mechanisms. That when you have this agent right here, this molecule right here, is abl... | Photosynthesis.mp3 |
You just have this P there. You just have this phosphate group there. But they really perform similar mechanisms. That when you have this agent right here, this molecule right here, is able to give away – let's think about what this means. It's able to give away this hydrogen and the electron associated with this hydro... | Photosynthesis.mp3 |
That when you have this agent right here, this molecule right here, is able to give away – let's think about what this means. It's able to give away this hydrogen and the electron associated with this hydrogen. So if you give away an electron to someone else, or someone else gains an electron, that something else is be... | Photosynthesis.mp3 |
Let me write that down. Good reminder. Oil rig. Oxidation is losing an electron. Reduction is gaining an electron. Your charge is reduced when you gain an electron. It has a negative charge. | Photosynthesis.mp3 |
Oxidation is losing an electron. Reduction is gaining an electron. Your charge is reduced when you gain an electron. It has a negative charge. So this is a reducing agent. It gets oxidized by losing the hydrogen and the electron with it. I have a whole discussion on the biological versus chemistry view of oxidation. | Photosynthesis.mp3 |
It has a negative charge. So this is a reducing agent. It gets oxidized by losing the hydrogen and the electron with it. I have a whole discussion on the biological versus chemistry view of oxidation. But it's the same idea. When I lose a hydrogen, I also lose the ability to hog that hydrogen's electron. So this right ... | Photosynthesis.mp3 |
I have a whole discussion on the biological versus chemistry view of oxidation. But it's the same idea. When I lose a hydrogen, I also lose the ability to hog that hydrogen's electron. So this right here, when it reacts with other things, it's a reducing agent. It gives away this hydrogen and the electron associated wi... | Photosynthesis.mp3 |
So this right here, when it reacts with other things, it's a reducing agent. It gives away this hydrogen and the electron associated with it. So the other thing gets reduced. So this thing is a reducing agent. What's useful about it is when this hydrogen, and especially the electron associated with that hydrogen, goes ... | Photosynthesis.mp3 |
So this thing is a reducing agent. What's useful about it is when this hydrogen, and especially the electron associated with that hydrogen, goes from the NADPH to, say, another molecule and goes to a lower energy state, that energy can be used in the dark reactions. We saw in cellular respiration the very similar molec... | Photosynthesis.mp3 |
As it gave away its electrons and they went to lower energy states. But I don't want to confuse you too much. So the light reactions, you take in photons, you take in water, it spits out oxygen, and it spits out ATP and NADPH that can then be used in the dark reactions. And the dark reactions, for most plants we talk a... | Photosynthesis.mp3 |
And the dark reactions, for most plants we talk about, it's called the Calvin cycle. And I'll go into a lot more detail of what actually occurs in the Calvin cycle. But it takes in the ATP, the NADPH, and it produces, it doesn't directly produce glucose, it produces a, well you probably saw this, you could call it PGAL... | Photosynthesis.mp3 |
But this can then be used to produce other carbohydrates, including glucose. If you have two of these, you can use those two to produce glucose. So let's just take a quick overview again, because this is super important, I'm going to make videos on the light reactions and the dark reactions, those will be the next two ... | Photosynthesis.mp3 |
We didn't even know that genes were actually the mechanism of heredity until the middle of the 20th century, and the direct modification of genes for some purpose really didn't even start happening until the 1970s. But it's worth noting that human beings have been in some ways influencing the genetics of organisms for ... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
But today in our lives, we also have things that look like this. Now these dogs did not come about naturally. They came about from many generations of breeding, of human beings taking things that started off looking like wolves or foxes and selecting for certain traits. They might have selected for traits that maybe th... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
They might have selected for traits that maybe they're small and they look more like puppies even when they're full grown, or traits that they are more docile, they're more likely to listen to what a human being says to do, or traits that they're good at killing rodents, or whatever else it might be, and over time, rep... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
Similarly, if you look into the plant kingdom, when you go to the store and you see that sweet apple, things like that might not have existed in the form that you see them today. It is very likely, in fact, most agricultural products, people might have found wild apples, and we could be talking thousands of years ago, ... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
And they might have found that the apples were a little bit sour and small, and hard to eat and hard to digest, but over time, people selected the trees that had sweeter apples, that had larger apples, and made the conditions so that they were more likely to reproduce, so over time, you got larger and sweeter apples li... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
But with that said, in the last few decades, we've been able to become much, much more precise with influencing DNA through genetic engineering. In other videos, we'll go more detail about how that is done, but you have this idea of recombinant DNA, combinant DNA, where you could take genes from one organism and put th... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
Well, let's say that there's a tree you wanna grow. Let's say it's an apple tree. But it's very susceptible to a certain type of disease, and if that disease hits, you lose all of your crop. But what if you could insert into the DNA of that apple tree maybe a gene that makes it more resistant to that disease? And this ... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
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