so in the previous video when we were talking about oxidative phosphorilation and chemiosmosis I said to you that the oxygen is the final electron acceptor in fact that is the only role of oxygen during aerobic respiration I just want to talk a little bit about what happens if oxygen is not present and how can that be detrimental to us so what you have here is the inner m of the mitochondrian you can see the electron transport chain uh ATP synthes and the inner membrane separates the two uh areas inter membrane space and the Matrix of the mitochondria so if oxygen is not present what happens now remember in CP cycle link reaction and glycolysis it gives you a total of 10 reduced nads when the glucose is broken down right if you look at that diagram so what I'm going to do here is I'm just going to draw out six reduced Neds um you don't have to memorize this part but it helps okay now remember what must happen to the reduced enery is first reduced en will release its hydrogen by undergoing oxidation and that hydrogen will split into protons and electrons and that electon if you notice the one that I highlighted uh it is moving along the electron transport chain the ETC and it will occupy the final part of the ETC right there and the hydrogen ion is pumped against the concentration gradient because remember as the electron moves along the ETC energy is released and that energy is used to pump hydrogen ions into the intermembrane space uh what I want you to focus on is the NAD and the NAD is regenerated so it can go back to glycolysis link reaction or crab cycle to transport more hydrogen atoms now look at the second reduced Ned uh that second reduced Ned also under goes oxidation the hydrogen atom splits the electron moves along the electron transport chain but notice that second electron cannot go all the way until the end because the earlier electron is occupying that final spot so the second electron has to occupy one spot before it but it still moves along the ETC and um the hydrogen ions are pumped against the concentration gradient so far so good and that NAD has been regenerated third reduce NAD same thing happens oxidation becomes hydrogen atoms and NAD electron moves along the ETC but it cannot go all the way um it just goes to the midpoint because there are two more electrons at the front occupying the ETC still pumps out hydrogen ions into the inter membrane space Ned goes back to you know transport more uh hydrogen atoms from glycolysis link reaction crap cycle fourth one same thing happens all right and the Ned is regenerated fifth one same thing happens Ned regenerated now look at the sixth one over here there is one reduced Ned coming along but the problem is the ETC is fully occupied with electrons the electrons are not moving at all so this is an issue so the first problem over here is the electron at the back is trying to tell the electrons at the front please move okay we need to continue flowing along the ETC but the electrons in the front are like no sorry we are stuck here all right so under normal circumstances oxygen has to be there to accept the first electron so that the second electron can move and move and move and this can continue to happen but this is not happening correct so the problem here is if oxygen is not present the other reduced Ned cannot be oxidized because it needs to undergo oxidation and the hydrogen because the the one that I'm circling there you don't have to know that in detail but that part of the ETC helps to oxidize the ruce Ned but it cannot oxidize the ruce Ned because it's occupied with an electron that's an issue so because the ruce Ned cannot be oxidized okay you will not be able to get hydrogen atoms and NAD and the problem is the NAD is not regenerated and what happens if all the nads and fads are not regenerated well very simple in this case over here you see uh it will stop the glycolysis it will also stop the link reaction and it will also stop the Decap cycle because remember for these reactions to happen they need nads and fads so without nads and feds being regenerated all these reactions stop and that's a big issue so if you notice okay look at my writing here I only said that link reaction and CP cycle stops because they require nads and fads to function I did not mention anything about glycolysis even though gly olysis also requires Ned by the way I'm going to explain that later because even when there's no Oxygen glycolysis can continue I will elaborate on that in the next video when we are covering anerobic respiration but the first point here is if oxygen is not present Neds even though in my video I'm just putting Neds in the exam please mention Neds and feds are not regenerated and because they are not regenerated link reaction and crap cycle will stop the second problem is because there's no Oxygen to accept the electrons the electrons in the ETC are no longer flowing they are not moving along the ETC so when the electron flowing in the ETC stops no proton they will not release energy and no protons are pumped into the intermembrane space and when no protons are pumped into the intermembrane space you will not have a proton gradient and guess what if you don't have a proton gradient no ch osmosis and if there's no chem osmosis no ATP synthesis synthesis will take place and I don't need to tell you what happens when your body cannot regenerate or synthesize ATP you die it's as simple as that so this is why oxygen even though oxygen has a very simple role all oxygen does is accept the electron It's the final electron acceptor during oxidative phosphorilation but if oxygen is not there you will not be able to regenerate your hydrogen carriers and um you will not be able to establish a proton gradient so ATP synthesis will completely stop as well