 This might be one of my favorite things in all biology. This, take a look at this and tell me where does the electron transport chain happen. Use my little diagram as a guide because if you look at this, you'll be like, whoa, really? Just like all our other pictures that I'm showing you, it's super complex. We're going to look, I'm going to draw you a picture of it, in a windy style, but this is taking place in the cell membrane of the mitochondria itself. It's actually taking place in that inner-folded mitochondrial membrane and the intermembrane space between my two membranes is really important to the function of the electron transport chain. All right, let's draw a picture. Here's what I'm going to tell you. You might as well have some visual that allows us to appreciate the fact that all of our electron carriers are going to the electron transport chain. They're headed there. They're on their way. And we're going to draw a picture of what they're going to find. Hey, we can't go that way. There's no paper there. You can go up. We're going to draw a picture. You ready? It's color-coded and it's color-coded to match the other images that I've drawn elsewhere. Okay, this I'm going to draw, I can't help it. I'm going to draw you a mitochondria. And here are my two membranes. Are you in agreement? And I'm taking a little slice like this, okay? I've got my cytoplasm up here. My outer mitochondrial membrane is purple. And then look at how I'm going to draw my blue inner mitochondrial membrane. I'm just going to draw it in a flat line. And I'm going to do that just so you can visualize that I've just taken a little slice. And this flat line actually, even though it actually is curving, I've zoomed in so much that it appears to be a flat line. Now, inside here is the mitochondrial matrix. And in between these, remember, is the intermembrane space. Intermembrane space. All right. And all of these are important anatomical locations to understand the function. Who is coming to this electron transport chain to determine her? Well, our electron carriers, and what do they have? There were 12 of them. And every single one of them is carrying two electrons. So watch, and there are 12 of them. 12 of them coming to do a job. I want you to look at this. I'm going to draw a totally diagrammatic view of a set of proteins that are embedded in the inner mitochondrial membrane. I'm going to draw another one right now while we're at it because I can't help it. This one is just about the coolest thing that ever existed. I'm going to draw it in here now and I'll tell you what happens to it. That thing is so awesome. All right, watch. First of all, in comes an electron carrier. The electron carrier delivers these high-energy electrons. Hands them off. It's like, hey, electron transport chain protein. I'm going to hook you up with some high-energy electrons. That's the first thing that happens. These proteins rock on. I'm cool with that. Go ahead and hand me those high-energy electrons. And then those high-energy electrons make sense they have energy in them. Guess what this guy does? This protein captures some of the energy in those high-energy electrons and says, okay, I'm going to use some energy to do some work. And the work that is going to be done is super random. Well, it'll appear random to you. You're going to be like, dude, really? What is this? The energy in the high-energy electrons is going to be used to pump hydrogen ions into the intermembrane space. And they're going in against their concentration gradient. That's how you know it's going to require energy. Who's providing the energy? The high-energy electrons that came from these carriers. I think of it as passing these electrons downhill. Now watch. This first protein uses a little bit of energy from these high-energy electrons and passes them off to the next protein, which then captures energy that is released. I think of it. I draw them to have kind of a potential energy, like you're passing these electrons downhill. And so if you're losing potential energy in these electrons as you pass them from protein to protein, I am guaranteed that there is a very clear chemical explanation for this. I just think of it as passing them downhill. And when you pass them downhill, energy is released and we capture that energy and use it to pump protons into this intermembrane space. The second buddy-buddy is going to do exactly the same thing. Using the energy that comes out of these high-energy electrons, it's going to pass them down. I can get orange. I really can. There we go. Pass them down. And each time we're releasing a little bit of energy that is captured and used to pump more protons into this intermembrane space. Really? Is anybody like going, why are we doing this? I am. Let me tell you. Oh my gosh, this is a true story. This is not a windification. Now we've got a whole bunch of protons in this space. And where do they want to go? They're like, ah, proton party. I'm sick of this party. Get me out of here. They want to get out. And this molecule is called ATP synthase. ATP synthase, you're going to think I'm lying and I am not. It's like a water wheel. It spins. And it spins in a circle when every time a hydrogen ion passes through it. There's a little thing in there that spins. And when it spins, guess what it does? Oh my gosh, this is so amazing. It takes ADP plus P and it produces ATP. I am not lying. This is what really happens. Oh my gosh, that is so phenomenal. So every time hydrogen ions pass through, we're able to make ATP. And in fact, it's like, I don't know, 30 ATP molecules from one molecule of glucose in the electron transport chain. Seriously? Now, we have 12 of these guys. And that's awesome. We can actually keep passing electrons on as long as we have a final electron acceptor. And I'm telling you, we need oxygen. We just keep on deciding. I can't decide what color to make it. Oxygen is my final electron acceptor. And I want you to think about this for just a second. It's why you breathe. It's why you need oxygen at all because you need oxygen to be the final electron acceptor. When oxygen grabs those two electrons, you'll also grab a couple of random hydrogen ions here. And ultimately, this is so phenomenal. It produces water. Are you serious? Take a look at your chemical equation and you will see that water is one of the byproducts. And oxygen is required if you don't have oxygen as your final electron acceptor. You're going to get a log jam. And your electron, your high-energy electron carriers aren't going to have anywhere to put their electrons. So the whole thing is going to back up. You're not going to get all that energy because it is anaerobic respiration, not aerobic. As long as you have oxygen, you've got aerobic respiration going on, which is...