 Okay everybody, Dr. O, in this video we're going to talk about the electron transport chain or the electron transport system. So we've already been through glycolysis, we've already been through the intermediate step, we've already been through the Krebs cycle. We generated a little bit of energy, we've made a total of 4 ATP, net gain of 2 during glycolysis and then 2 during the Krebs cycle. But as humans we had to spend two of those to get all these building blocks into the mitochondria anyways, so we've barely made any energy. Throughout this entire time we've been collecting what I call the casino chips, we've been collecting these full electron carriers that are now loaded down with electrons and hydrogen ions and we're going to cash them in, that's going to be where energy is produced. So this is called the electron transport chain, that's exactly what it does, but as you're going to see here at the end it's the movement of protons that actually generates the energy needed to make ATP. Before we move any further you see these H pluses all over the place, we can call them hydrogen ions or protons, now the reason we can call them either is hydrogen is the only element on the periodic table that doesn't have a neutron, so that means hydrogen is a proton and an electron, well a positive hydrogen ion has had its electron removed and that's why all that's left is a proton, so don't be confused by that. If someone's talking about proton pumps or proton pores or whatever, they mean the same thing as hydrogen ions and I think protons are probably a fine word there. Okay, so we're also looking at the process of oxidative phosphorylation, the energy made prior to this like during the Colossus where we weren't using oxygen was called substrate level phosphorylation, so this is going to be oxidative phosphorylation. Okay, so let's go through this, I know this is complicated, but we have all, we've brought in all these NADHs, remember NADH used to be NAD plus, it became NADH as it was loaded with electrons and hydrogen ions, FADH became this FADH too, so now they're going to come and dock on the electron transport chain and they're going to give up their electrons and their hydrogen ions, so NADH is going to be able to generate enough energy to lead to the production of 3ATP, FADH2 as you can see here, you know, kind of starts later and is able to generate enough energy to make 2ATP, so those are the kind of key things there. But the key thing to note is now you have all these hydrogen ions and all these electrons, as electrons are transported step by step through the electron transport system, each time an electron is removed or transferred it gives a little bit of energy and this energy accumulates and when you have enough energy from the movement or flow of electrons, you can now pump hydrogen ions, so these are hydrogen ion pumps or proton pumps and as electrons transfer through them they get a little bit of energy at a time and that gives them enough to pump out hydrogen ions, so we've been calling it the electron transport chain which it is, but it is this movement of hydrogen ions outside of this inner mitochondrial membrane in us, in bacteria this would be happening in the cell membrane and then back through is actually energy is going to be generated. So there you see the electron transport system, you have those three big proton pumps then you have your mobile electron carriers, just to make this clinically significant the poison cyanide will actually block that cytochrome C right there in the middle which is why people that are poisoned with cyanide, like in the movies where spies poison themselves rather than talk or whatever, they die relatively quickly, really quickly because if you shut off the electron transport system then you can no longer, the flow of electron stops which means that ATP production would stop as well. The other thing to note here is as these electrons are used up they need a final electron acceptor and that's going to be oxygen, so they're at the bottom of the image, oxygen is going to accept these electrons once they've helped the proton pumps work, oxygen is going to accept those electrons and become water, so this is why we need oxygen, we use aerobic respiration, oxygen is our final electron acceptor, there are other living things that don't use oxygen as a final electron acceptor but we need it, so without oxygen same problem, this is the reason that we breathe in is because if we don't get oxygen then we can't, we cannot generate ATP and this is also the reason we breathe out because as you've seen during the intermediate step and the Krebs cycle we produced carbon dioxide that we had to get rid of, so your metabolism is what requires oxygen and generates CO2, but okay so now we have it, we have, let's look up all these hydrogen ions here at the top, we've created a concentration gradient and for several reasons, number one, so there's more hydrogen ions outside of this mitochondria membrane than inside of it, so diffusion says that these are going to be slamming each other, they hate each other, they want to move, right, the example I use in classes is if each of these hydrogen ions had a jump rope and they were whipping each other they'd want to spread out, so they want to diffuse back into the cell, so just the fact that there's a concentration gradient is reason enough, but they also had, it's called an electrochemical gradient because they have the same a charge and likes repel each other, so electrically and chemically they want to leave, they do not want to be here and then you could also make an argument that because they're, they're hydrogen ions, they're positive, a little bit of a pH diffusion issue here too, but for, so for multiple reasons, two or three depending on how you want to look at it, these hydrogen ions want to get back inside the inner mitochondria membrane and if they do, they can, but let me go ahead and show you a little better image, you can see a little bit of the inside here, the cells, the mitochondria or the electron transition is fine, if you want to come back in that's fine, but you have to come in through this enzyme and this enzyme here is called ATP synthase, it's specifically called a protein poor complex, but ATP synthase is fine, as hydrogen ions or protons flow through it, it causes spinning, there's a turbine, it's basically an enzyme that's a turbine, so think about like a wind turbine, how when wind turbines spin they generate energy, hydroelectric energy is water causing turbines to spin, nuclear power plants generate steam to it's a steam driven turbine, so when things spin they generate energy, that's common in the world around you, it happens inside your cells too, so as these hydrogen ions flow through, these protons flow through ATP synthase, it causes it to spin and this turbine spinning generates the energy needed to take ADP and add that third phosphate to it to make ATP, adenosine triphosphate, so this process, the flow of hydrogen ions or protons here is called chemiosmosis, just in case you ever see that term, so in the end we needed all these electrons to power the electron transport system, so that we could pump a bunch of hydrogen ions out of the mitochondrial membrane or wherever this is occurring in bacteria and then as they as they flow back in, they generate the energy needed to make ATP, so this is why you have to eat every second right, you're either eating or your body's eating stored reserves because if you don't constantly keep these electron transporters bringing electrons, then the system shuts off and without electrons, you'd no longer be pumping these hydrogen ions and we wouldn't have this electrochemical gradient and they'd stop flowing and you would quit generating ATP, so alright, so that's the, I know this has been a lot but this is the, so we've now been through glycolysis, the intermediate step, the Krebs cycle and the electron transport system, so hopefully you now see how we've gone from food, glucose, our fuel to 36 ATPs in human and 38 ATP in bacteria, so you've done it, I hope you grasp it at least to some level, I get it, it takes a lot of time, maybe watch the videos more than once, come back in a few months and review this, it just, this is a very difficult process to understand and I hope you grasp it a little bit better now. Alright, I hope this did help, have a wonderful day, be blessed.