so and this I'm going to make this a kind of a short video lecture but I want to basically go over and explain the difference between substrate level phosphorilation and oxidative phosphorilation because these are um some common questions I get so let's step back actually and talk about what is phosphorilation and most of you probably already know this but I want to reemphasize it is that phosphorilation is the transfer of any molecule or sorry any phosphate okay to a molecule or a protein okay when a phosphat is added to something we typically call that phosphorilation so in most cases phosphorilation occurs by proteins called kinases okay these are enzymes that catalyze this phosphorilation sorry about that so typically um kinases use phosphate from a molecule of ATP to add to a molecule or a protein so let's get a pen on here real quick so what you'll see here is that you'll have a molecule of ATP all right the ATP has three phosphates on the end all right and one of the phosphates will actually be added to a molecule and that's phosphorilation it'll generate an ADP as a product okay so uh these are typically catalyzed by kinases and this is a very common reaction so that's phosphorilation all right so let's look more closely at what substrate level phosphorilation is so this is an event that occurs both in glycolysis and also in the TCA cycle and the definition that I really want you guys to know is that it's the synthesis of ATP by the direct transfer okay of a phosphate group from a substrate okay from some molecule that already contains it to a molecule of ADP so in that previous reaction I just showed you of um a molecule being phosphorated by ATP you can think of this as the reverse we're actually making ATP by phosphor ADP okay so again these reactions nevertheless are still catalyzed by enzymes called kinases all right and there are different names for them depending on the steps so every kise might have a different name but anything that can phosphorate something is a kinase all right so instead of the phosphate coming from ATP here the phosphat is coming from an existing molecule that we're going to call a substrate so you can see here one three phosphoglycerate has a phosphate there and a phosphate here and we're going to take one of these phosphates and combine it with ADP to make our ATP okay and you can see the phosphates missing here okay so this phosphorilation event occurred on the what we call the substrate level meaning that there's some kind of substrate reactant that was used to donate that phosphate and so that's what we refer to as substrate level phosphorilation so in this reaction from glycolysis one 3 bis phosphoglycerate becomes three phosphoglycerate by phosphoglycerate kinase and it makes one molecule of ATP by substrate level phosphorilation now this reaction can actually work in Reverse so if you take ATP okay you can take that phosphate phosphorate this and create one three bis phosph again okay so this is a phosphorilation reaction but the synthesis of ATP by the transfer of phosphate to ADP is what we consider substrate level phosphorilation and if you remember from our free energy lectures that these molecules that contain uh phosphates on them are high energy intermediates so this is a favorable reaction to occur so that's substrate level phosphorilation let's look at another example of substrate level phosphorilation here's 13 bis phosphoglycerate again um plus ADP I'm sorry this is the same example I gave you earlier um to make three phosphoglycerate and ATP okay so if I show you this reaction and I ask you what type of reaction this is you should know that this is substrate level phosphorilation but you also should know that the chinise is responsible for this reaction right so that's substrate level phosphorilation you'll know it's substrate level when when what you're seeing is the phosphates dona at from some kind of molecule or reactant okay so that's substrate level so now what's oxida phosphorilation so oxidative phosphorilation is is still we're talking about the synthesis of ATP okay let me go to my pen again so we're still synthesizing ATP but we're doing so in a different way we're actually oxidizing these electron carriers n ADH and we're also doing this to fadh2 all right we're combining oxygen to oxidize these molecules in order to generate ATP but it's not on this same it's not this type of phosphorilation we're not taking a phosphate from anywhere here from a substrate and putting it onto ADP we're actually taking ATP ADP and pi and combining them together in a canical reaction all right and that's how we're synthesizing ATP so it requires oxygen to oxidize the electron carriers to provide the force or the energy to do this mechanical synthesis of ATP and that's referred to as oxidated phosphorilation and this occurs only in the electron transport chain okay so substrate level occurs both in glycolysis and TCA and oxidative occurs in the electron transport chain so let's look real closely at what this means so we're going to go into more detail about this when we get to the electron transport chain but what I want to show you is kind of what happens so remember the ETC occurs on the mitochondrial inner membrane so this is mitochondrial inner membrane oops sorry about that and on the inner membrane are a series of enzymes that's why it's called the electron transport chain but let's just draw let me draw the pl membrane again so you know it's lipid Bay or something like this let's just draw one little globular thing let's call this the entire electron transport chain this is the ETC and we're going to show I'll show you exactly how this works later in the semester but what happens is our nadh or our fadh2 come into the ETC okay and they react with oxygen molecular oxygen and they become oxidized and what happens is you generate the oxidized form so NAD Plus or fad another byproduct from this is water okay because we're taking the electrons and the hydrogens that these are carrying combining it with oxygen to make water that's why one of the main byproducts of CYO respiration is water this reaction provides a force right and you don't need to know what it's called yet we'll get to it later but the force is given to a protein all right in the m in the mitochondria that's called ATP synthes and you don't need to know this for this test but just in case you're curious and what ATP synthes does is it basically takes ADP and it takes inorganic phosphate floating around and it forms a TP okay so it takes these two molecules and just pushes them together to actually form a molecule of ATP so we're not transferring phosphate from a molecule to ATP we're taking just free floating inorganic phosphate molecules combining them with ADP to form ATP okay and that's oxidative phosphorilation so let's go back and review real quick substrate level phosphorilation is and the both substrate level and oxidative phosphorilation are the synthesis of ATP okay so just remember that that you have to you're synthesizing ATP for this substrate level is the synthesis of phos of ATP by the the transfer of a phosphate Mo group from a molecule or a substrate some kind of reactant to a molecule of ADP to form ATP oxidative phosphorilation is the use of oxygen to oxidize electron carriers in order to generate some kind of force that will actually push together ADP and pi to form ATP so hopefully I cleared that up um if you're more confused about this please let me know um and we can go over it again but but I really want you to understand the difference between the two I want you to know in which stages I'm sorry which stages of cellular respiration um do each one of these things occur and obviously I would like for you to be able to recognize the reaction so if I show you a reaction like this one here I would like for you to tell me that that's substrate level phosphorilation and not oxidative phosphorilation and vice versa