when we looked at glycolysis and the conversion of pyruvate to acetal COA and then the Krebs or the citric acid cycle we were sometimes directly producing atps but we were also doing a lot of reduction of NAD to nadh and we later said that that nadh that that can later be oxidized to and that energy from that oxidation that energy that's released from the electrons can be used to actually create ATP and nada is the main character here but there are other co-enzymes that are involved like co-enzyme 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 co-enzymes and that process is what we call oxidative phosphorilation oxidative oxidative phosphorilation now the main player when we're talking about cellular respiration and oxidative phosphorilation 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 has if we just look at if we just look at this reaction from the point of view of nadh being oxidized remember oxid oxide oxidation is losing electrons so NAD plus and then you're going to 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 into NAD 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 molec Ule it can release a lot of energy and the eventual acceptor of those electrons and I can show the the corresponding reduction reaction is we have two electrons two electrons plus two hydrogen protons or really just two protons a hydrogen nucleus is is just a proton it doesn't have a neutron for the the main isotope of hydrogen so two protons plus half of an oxygen molecule yielding you put all of these two 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 oxygen likes to be doing oxid likes to oxidize things that's where the whole word oxidation comes from so here or one another way thing 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 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 phosphorilation is all about doing this in a series of steps 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 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 going to go these electrons they're going to be transferred and I won't go into all of the details 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 co-enzyme co-enzyme Q and A cytochrome cytochrome C and that keeps going to different things eventually eventually getting to this state right over here to where those electrons can be accepted by the by the wa by the oxygen to actually form the water 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 a second is being used to pump hydrogen protons across a membrane and we're going to 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 on a on a mitochondria so this is mitochondria let's say that's our mitochondria and let's let me draw the inner membrane and then these folds in the inner membrane the singular for them is Christa if we're talking the plural is Christi so we have these folds in the inner 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 between the outer and the inner membrane the space right over here that is the intermembrane space inter membrane membrane space and then the space inside the inner inside the inner membrane let me make sure you can read that space properly this this space over here this is the Matrix this is the Matrix and that is the location of our citric acid cycle or our kreb 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 co-enzymes in some books or class classes you might hear about fad being reduced to fadh2 which can then be oxidized as part of oxidated phosphorilation other times people say well actually that's going to be attached to an enzyme and then that fadh2 is be is used to reduce co-enzyme Q to produce qh2 and then that participates in oxidated phosphorilation so you could think about either one of these I'll focus on Q2 well we'll actually focus on nadh because it's all a similar process fadh2 or Q2 enters a little bit later down this process so they don't produce as much as much energy but they still can be used to help produce ATP but anyway our our citric acid cycle which we should 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 in a color that we can see so if I were to zoom in right over there let's show this fold in the inner membrane and it's very and make it let's make it clear that this is like all of these membranes these are all phospholipid by layers so let me let me draw I'm doing the same color that I you that I did in the the actual diagram so we have we have all these we have a by layer of phospholipids and I'm clearly not drawing any of this stuff to scale [Music] so uh almost done all right 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 phosphorilation and these the this this chain of of enzymes chain of proteins is what we call the electron or is what we call the electron transport chain so let me draw that so maybe this is one protein and I I'm just drawing them as kind of these abstract abstract and you could refer to the electron Transportation as either these proteins or you could view as this process of these electrons going from one acceptor to another eventually making its way all the way to the oxygen so that might be one protein 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 going to 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 D+ so it just became oxidized those elect Rons will go to an acceptor which then get transferred to another acceptor they get transferred to another acceptor and goes through this electron transport chain and as that energy is released that energy is used to pump hydrogen protons from The Matrix so this side right over here the left side right over here this is the Matrix 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 uh and they're releasing energy as they go down this kind of uh to to towards more and more electr negative things that they feel more comfortable with the water than they feel than they felt with the nadh and by doing so by these electrons going down that gradient I guess you could say or or maybe a better way from going from a higher energy state to a lower energy State we are creating this proton gradient so the concentration of protons on the right side of this membrane and we just to be clear where this is this space right over here this is right over there that's the intermembrane space where the hydrogen proton concentration is building up now this is stored energy because this is a this is a electrochemical gradient all this positive charge they want to get away from each other they want to 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 want to go down their concentration gradient into the Matrix there's less of the protons here there's less of the protons on the in The Matrix than there are in the inter than there are in the in intermembrane space and so there 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 little bit is using using a protein called ATP synthes ATP syn it's actually a protein complex I should say so ATP synthes really an enzyme and ATP synthes goes across it's actually a fascinating fascinating molecule I'll show a better diagram of it in a second but your ATP synthese goes across the membrane and actually has a 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 then it actually has something you can view this as a 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 electrochemical gradient so these Hydro hydrogen protons go down and they actually cause the axle to spin and so maybe I'll draw it this way they actually cause they actually cause the axle to spin as they go as they go down their electrochemical gradient and as this axle spins and this axle you know it's not this smooth it's not like it's made out of metal or something it's made it's made out of amino acids so it's got this it's all bumpy and 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 then a phosphate group and they have actually three different sites where this can happen so that's an ADP and a phosphate group there's another site that I'm not drawing but as this thing rotates it essentially keeps changing the confirmation 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 they no longer attach to the active site and they let go so you have this this 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 a electricity 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 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 this is how I'm generating my energy this is a a a more accurate depiction of ATP synthes right over here and based on this diagram this is our this this let me make sure I'm so this right over here I'm having trouble I'm having trouble drawing on on this 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 by layer so if I wanted I could draw the the by layer 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 Christa and so the hydrogen protons they build up they build up in the intermembrane space because of the electron transport chain and then they flow down and then they flow down their con their electrochemical gradient turn this rotor and then they cause the creation of the atps over here so you have you know ADP ADP plus a phosphate group and then you produce and you produce your ATP so you know 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 you 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 produce some atps directly through glycolysis and through the citric acid cycle but mostly most of the energy is because of the reduction of these co-enzymes and especially NAD to nadh and then in in in oxidated phosphorilation and the electron transfer chain we can use the oxidation of the nadh to pump hydrogen protons from The Matrix to the intermembrane space and then let them get go back through through the ATP synthese which jams the phosphate into the ADP to produce the ATP which is our our biological currency of energy