hey everyone in this video i'm going to go over the bare bones of what you need to know about cellular respiration for ap biology remember the whole point of cellular respiration is how cells get energy from biological molecules to make atp the currency for cellular energy now as i go along with these notes feel free to draw along with me i'll also post a scanned version of this finish drawable notes at the end of this video if you'd like to use that all right i apologize for advance for my messy handwriting but let's get started in eukaryotic organisms cellular respiration involves a series of enzyme-coordinated reactions and there are three main steps that we're going to go over today the first is glycolysis the second is the krebs cycle also known as the citric acid cycle and the third is the electron transport chain that also goes along with oxidative phosphorylation now to remember all these steps in order i have a quick mnemonic and that's going crazy can offer purpose going crazy can offer purpose of course crazy spelled with a k all right let's get a little bit closer into each of these steps let's take a look at glycolysis remember nearly all existing organisms perform glycolysis glycolysis happens without oxygen and glycolysis only occurs in the cytosol all three of these things can provide us with justifications that glycolysis first occurred in a common ancestor of nearly all living organisms so it's important to remember that glycolysis occurs in the cytosol of a cell not in the mitochondria but it's still our first step in cellular respiration glycolysis is where the catabolism of glucose begins remember catabolism is just the breakdown of a molecule for energy the things we get out of glycolysis include pyruvate which will then go through its own oxidation to produce acetyl coenzyme a that's called pyruvate oxidation and it'll happen before these molecules enter the krebs cycle we'll also get two nadh which will help us take electrons to the electron transport chain later on it's important to remember again that glycolysis is the catabolism of glucose so if you remember all of this is happening outside of the mitochondria in the cytosol so now let's draw part of our mitochondria so that we can illustrate the rest of the process now i'm going to draw the cristae or the inner folds of the mitochondrial membrane if we were to zoom into one of these we would see a phospholipid bilayer our next main step is going to be the krebs cycle also known as the citric acid cycle this takes place in the inner mitochondrial matrix an important thing to remember is that our pyruvate that is broken down during the last steps of glycolysis is now broken down here into carbon dioxide and water we talk about the net reaction of cellular respiration and getting carbon dioxide as a byproduct this part of the process is where that carbon dioxide comes from now you need to know that the krebs cycle is indeed a cycle but you don't need to know all of the steps or the different molecules produced throughout the entire cycle it's called a cycle because the final product is actually going to be the exact molecule that we need to accept the acetyl coenzyme a to start another turn of the cycle but for now all you need to know is that it's a cycle and what comes out of it this part of the process also generates a little atp carbon dioxide like we already talked about nadh and fadh2 these two are what we call coenzymes their job here is to transfer electrons to the electron transport chain these will later bind to an enzyme to get the reaction started another way to summarize the krebs cycle is that it's the oxidation of intermediates meaning we have the loss of electrons that will later be transferred to the electron transport chain molecules that lose electrons are oxidized all right now let's move on to the final step the electron transport chain and oxidative phosphorylation it's important to remember that this last step happens across a layer the inner mitochondrial membrane we need this barrier here in order to set up the gradient that's later going to go into the process of generating atp now there are several important enzymes that are going to be along this membrane but the only one you need to know about and that you need to know the name of is atp synthase this is a proton pump and it's going to help create atp hence synthase atp synthase now when we have the electrons pass through different molecules in a sequence of reactions an electrochemical gradient of protons or hydrogen ions is going to occur across the membrane eventually we'll establish a gradient with lots of protons on one side this will help generate the movement of our proton pump so that we can synthesize atp from adp in our final step our proton pump atp synthase generates a lot of atp in this part around 34. now this is called the electron transport chain as electrons flow through these different proteins but the electrons have to go somewhere and they're finally going to be accepted by oxygen at the very end of this process oxygen is the final electron receptor and which is why it's needed in cellular respiration and here water is generated as a byproduct the most important things to remember about our electron transport chain is that we have a flow of protons through our membrane-bound atp synthase which will generate atp this provides the energy for our oxidative phosphorylation of adp to atp all right let's take a look at this whole thing one more time glycolysis releases energy in glucose to form a little bit of atp which i forgot to mention the first time an nadh pyruvate generated in that process then is transported from the cytosol into the mitochondria where we have more oxidation and we get acetyl coenzyme a this will go directly into the krebs cycle where we have carbon dioxide released and more atp synthesized then we get the oxidation of different intermediates so we can get the transfer of electrons to go into the electron transport chain all the electrons extracted during glycolysis and the krebs cycle are transferred by nadh and fadh2 into the electron transport chain that occurs across the inner mitochondrial membrane as these electrons are transferred between our different reactions we'll establish a gradient of protons this will then help atp synthase generate atp from adp through oxidative phosphorylation this will generate a lot of atp other molecules involved in cellular respiration you won't need to memorize for the ap bio exam but you should be familiar with the ones i mentioned here thanks so much for watching and i'll attach my version of this drawing notes to this video feel free to make your own with any other sort of illustrations thanks for watching