for this video we are going to be looking at the final part of aerobic respiration which is known as oxidative phosphorilation together with chemi osmosis before we go into uh the process there is a bit of revision that we have to cover all right because this process is a little bit complicated now the first thing I want to talk about was in the previous video I'm just putting it on the screen here as you can see um in one of the previous videos I said that the main way to produce ATP is through a process known as CH osmosis and CH osmosis involves uh an enzyme known as ATP synthes it's a membrane enzyme membrane enzyme meaning to say it's an enzyme but it's attached or embedded in a membrane it cannot just freely move around in the cytoplasm and the way this enzyme functions is uh as long as the enzyme is given uh adequate energy the enzyme is able to accept ADP and phosphate and then it's able to synthesize ATP for the enzyme to function it needs to be powered by hydrogen ions as you can see in that diagram hydrogen ions will diffuse down the concentration gradient from a higher hydrogen ion concentration to a lower hydrogen ion concentration it Powers the ATP synthes and thus the ATP synthes is able to produce ATP this is the main way our cells produce ATP by the way so that's the first thing we covered so the second thing we want we want to talk about was I told you that oxidative phosphorilation and chemiosmosis happens in the inner mitochondrial membrane so if I'm drawing out a mitochondrian over here you can see the The Matrix the Christi the Christi are the finger like structures meant to increase the surface area of the inner mitochondrial membrane okay now the blue color area that I'm highlighting there is known as the intermembrane space the inter membrane space is just an area between the outer membrane and Inter inner membrane this is important and I'm uh coloring The Matrix as green in color now please don't judge My Coloring yes I know it's not hitting the lines okay you can see those gaps those gaps of whites and such but yeah it's it's kind of difficult to color with it um anyway so uh I had one of a student I had one of my students who say teacher can you not because uh some of my students were like I I guess you can say they have some sort of OCD if you can call it that where if they see me not color it properly they they cringe but who cares anyway so um the thing that I want to cover here is I want to okay I want you to know where the ATP synthes is located as you can see I drew out an ATP synthes there remember it's a membrane enzyme right so where exactly is the ATP synthes found it is actually embedded in the inner mitochondrial membrane now some students assume that the mitochondrian only has one ATP synthes no the mitochondrian can have a multitude of ATP synthes as long as it's within the inner mitochondrial membrane that is why the inner membrane is folded because the more folded it is the more ATP synthes it can contain right and remember how does the ATP synthes function the ATP synthes can only function when hydrogen ion diffuses through it so in this case the intermembrane space must have a higher hydrogen ion concentration and the Matrix must have a lower hydrogen ion concentration not the other way around so that the protons or the hydrogen ions can diffuse through the ATP synthes power the ATP synthes and thus ATP can be synthesized so the question here is as follows so the first question was where what is the main way we produce ATP we do it through chemos osis and we use the ATP synthes where is the ATP synthes located in this case it's located in the inner mitochondrial membrane how does it function hydrogen ions will have to diffuse down the concentration gradient from the intermembrane space to The Matrix through the ATP synthes and as long as that happens the ATP will be continuously synthesized then comes the question okay so where does the Hy hen ion come from right so this is a very simplified diagram that I'm drawing here okay you can see that uh uh okay I know the ATP synthes has a more complicated structure but I'm just simplifying it over here so that uh in the exam usually they'll draw ATP synthes out like this so you have the inner membrane which is a phospholipid Bayer on its own uh it has the blue color area inter membrane space and also the Matrix okay right that's good now so this is where the video is all about where we are going to talk about how exactly do we generate that proton gradient okay now to talk about that we first have to cover a structure which is nearby the ATP synthes and that is known as the electron transport chain also known as the ETC if I'm not mistaken you can say Etc in the exam by the way so that's fine all right so and the etcs are also located usually Lo at next to every ATP synthes so before we talk about oxidative phosphorilation and CH osmosis we then also have to cover what exactly does the ETC do electron transport chain it's in the name the electron transport chain is a series of membrane proteins all right and what it does is it just transports electron okay so it accepts electron and passes the electron from one protein to another and as the electrons are passed along the chain the electrons release a little bit of its energy because at the beginning the electron was full of energy and as the electron gets passed around the electron loses its energy now you might be thinking oh this is a bad thing the electron is losing energy but no it's actually quite good because that energy will power some of the proteins in the electron transport chain as I represented here and because it powers the ETC some of those proteins are now able to pump hydrogen ions against the concentration gradient and it pumps it into the intermembrane space so you might be thinking okay but why the hell is all this happening well very simple if you pump hydrogen ions into the intermembrane space compare the hydrogen ion concentration in The Matrix and the um intermembrane space the intermembrane space has a higher hydrogen ion concentration The Matrix has a lower hydrogen ion concentration so what process can happen the hydrogen ions diffuse through the ATP synth this through chemiosmosis and by doing that ATP can be synthesized then of course comes the question where exactly does the hydrogen ion come from where does the electron come from because for the etc2 function it needs electrons it needs hydrogen ions right so we've talked talked about it remember when we studied glycolysis link reaction and crap cycle the organic molecule like glucose was constantly broken down and as it was broken down it released out hydrogen and the hydrogen was accepted by reduced Neds and reduced feds so this is where the reduced Neds and reduced feds are going to be used so the first step in oxidative phosph for relation is the fact that the reduced NAD has to be oxidized what does it mean by oxidized it will release the hydrogen atom not hydrogen ion hydrogen atom first be careful and when it releases the hydrogen atom what happens to the reduced NAD the reduced NAD is reconverted back into n which is like a carrier which is empty the NAD can go back to the link reaction and crap cycle or glycolysis and carry more hydrogen okay if it wanted to but let's focus on the hydrogen atom right now that hydrogen atom is the one that will split to become hydrogen ions and electrons then you might be thinking oh okay yeah we were just talking about electrons and hydrogen ions earlier that is where they come from by the way now the hydrogen atom does not spontaneously split by the way one of the prot in the ETC helps that process happens but we don't have to go through that in detail um so what happens to the electron the electron will then move along the ETC and remember the electron had high energy and that electron will release its energy along the ETC but for the exam you can just say the electron moves along the ETC and Powers it that's good enough and as it Powers the ETC the ETC or the electron transport chain will power pump the hydrogen ions from The Matrix into the intermembrane space and when it pumps it into the intermembrane space look at the concentration of the hydrogen ions in the intermembrane space and the Matrix what do you notice the hydrogen ion concentration or the proton concentration in the intermembrane space is higher in The Matrix is lower thus number five you have created a proton gradient a proton gradient just means that one area has a higher hydrogen ion concentration one area has a lower hydrogen ion concentration and as is with most things in the universe they will always want to strive towards equilibrium which means to say they want to diffuse through something okay to rebalance the gradient so what does the hydrogen ion do the hydrogen ion diffuses through the ATP synthes and that process is called chemiosmosis and as long as hydrogen ions diffuse through the ATP synthes the ATP synthes is powered and ATP is synthesized that is what happens in this case so you might be thinking okay this is this is simple enough now the final step of this process in oxidative phosphorilation and chem osmosis remember if you notice something we have only we we have been talking about aerobic respiration and aerobic respiration is all about using oxygen but up until now I've not mentioned anything about oxygen gas at all if you've noticed in in my video on glycolysis link reaction clap cycle never once did I mention oxygen gas even though oxygen is super important you see the role of oxygen in aerobic respiration is quite anticlimactic okay the oxygen is only important for the final part or the final step where oxygen accepts the electron from the ETC and it also accepts the hydrogen ion to form water so the electron from the ETC will bind to the oxygen the hydrogen ion in The Matrix will also bind with oxygen and it becomes water in the exam if a question asks you what is the role role of oxygen or the function of oxygen you just have to say It's the final electron acceptor now you might be thinking that's it is that all oxygen does yes that's basically what it does uh but that does not take away from the importance of oxygen by the way because if the oxygen is not there uh oh it's going to be difficult you will die I mean obviously right if you stop breathing or if you are in an environment where there's not enough oxygen I don't need to tell you what will happen but we will talk about uh that later in the next video but for now okay this is the entire process of oxidative phosphorilation and chemiosmosis let's do it again simplified version the reduce we start off with the reduced NAD and the reduced NAD will be oxidized to become hydrogen atoms and nads the hydrogen atoms splits to become hydrogen ion and electron the electron moves through the ETC and it provides energy to the ETC and when the ETC has energy the ETC will pump hydrogen ions against the concentration gradient into the intermembrane space this creates a proton gradient between the intermembrane space and Matrix and the hydrogen ions or protons will diffuse through the ATP synthes through chemiosmosis causing the production of ATP to happen oxygen is the final electron acceptor where it will receive electron together with hydrogen ions to form water to summarize every everything we've learned in aerobic respiration glucose is broken down in glycolysis to form two pyate the two pyro is broken down to become two acety COA in link reaction and the two acety COA or the acety group is broken down completely in CP cycle these processes will produce two reduced Ned in uh glycolisis two reduced Ned in link reaction and six reduced nads in CP cycle to together with two reduced fads and it also produces net 2 ATP in glycolysis net 2 ATP in CP cycle we've covered that before those reduced Neds and reduced feds will go towards the inner membrane of the mitochondria where those reduced hydrogen carriers will become oxidized they will release the hydrogen atoms and then look at what happens to the reduced Neds and reduced feds they are regenerated okay and then the hydrogen atom splits to become hydrogen ion and electron electron moves through the etc etc pumps hydrogen ion against the concentration gradient into the intermembrane space creates a proton gradient hydrogen ion diffuses through ATP synthes and ATP synthesize and finally the electron in the ETC will be accepted by oxygen which is the final electron acceptor and that forms water now I want you to notice with the regenerated Neds and regenerated feds where do they go back they will then go back to glycolysis link reaction crap cycle because they have to carry more hydrogen atoms towards the inner membrane so this so the remember the the feds and Neds are Transporters they are carriers they carry the hydrogen atom to the inner membrane release the hydrogen go back like a car or a taxi or an Uber or a grab whatever and carry more hydrogen atoms over and over again this is the summary of everything in aerobic respiration