hi everyone and welcome to chapter 7 in this chapter we're looking at cellular respiration or the metabolism of glucose to generate energy usually in the form of ATP to power the different types of reactions in our cells so if we think about why we eat one of the main reasons is to get energy so we have to eat something like carbohydrates we have glucose for example and the potential energy stored in the carbon carbon bonds within glucose if we break down those bonds energy is released that we can use to power different types of biochemical reactions inside cells or we can save that energy to use it later and this form of saving the energy is usually through the production of ATP so this process of glucose catabolism breaking down glucose for energy is also known as cellular respiration and we're going to look at that today the focus of this chapter as we go through the different types of metabolic Pathways that are part of cellular respiration we're going to see that there are many many small steps or small transfers of energy Within These Pathways and they all involve the movement of electrons so as we go through the chapter you're going to see these high energy electron carriers like nadh it started as NAD the oxidized form and it captures electrons creating a higher level of potential energy you'll also see these molecules fad which is the oxidized version becoming the reduced version fadh2 and these molecules I call them high energy electron carriers because they have high potential energy when they are in their reduced State and we'll talk about that more soon we the reason we have so many of these high energy electron carriers is because we want to make sure that when we're chopping up the carbon carbon bonds in glucose that we don't release energy all of the sudden and lose a bunch of it as heat we want to be as efficient as proper as possible and we can do so by creating these small intermediates these high energy electron carriers as well as capturing energy in ATP as well interestingly the final equation we're going to see or the over overall equation for cellular respiration is shown down here where we're going to take glucose break it down and we need an input of oxygen for cellular respiration to occur once we chop up the glucose I can see glucose has six carbons so it makes sense that I'm going to generate six carbon dioxides as my product or partial part of my product I generate some water and then I capture the energy in those carbon carbon bonds in the form of ATP when you light a match you're doing the same thing A match is basically cellulose right fiber we are giving it oxygen we need oxygen to create fire we light the match and what's happening is this reaction is happening right away this whole reaction really and I see this part but instead of capturing the energy in the form of ATP the fire is generated the heat is generated instead of ATP since we break down glucose in many many small steps to capture energy within each step and be more efficient without losing energy in the form of heat or as much energy in the form of heat we do this by generating those high energy electron carriers nadh and fadh2 through redo reactions so redo reactions are chemical reactions where we are transferring electrons between molecules reducing a agents are molecules that donate electrons to someone else so they reduce someone else and thereby they become oxidized oxidizing agents will oxidize another molecule by accepting electrons so therefore they get reduced so let me show you this down here so I can see ah is a reducing agent it's going to reduce someone else and it looks like that someone else is the oxidizing agent over here so here you're going to transfer your electrons to someone else and after you do that you become oxidized on the other hand the oxidizing agent will be oxidizing this guy over here and by doing that the oxidizing agent will become reduced so we know that anything that gains electrons is reduced and anything that loses electrons is oxidized you might have heard of This Acronym to to remember this um some s uh some professors use lose electrons means oxidation gain electrons means reduction so I think how people remember this is by saying Leo the Lion says G if I look at a couple of other examples I can see that sodium is becoming oxidized so this must have been the reducing agent reducing agents become oxidized and let's see the other one must be the oxidizing agent because oxidizing agents become reduced and then another way to remember what is reduced or oxidized you can use the acronym oil rig so oil reminds us that oxidation is lose electrons and for the rig it's reduction is gain electrons so whatever works best for you to remember what is reduced or oxidized you can use either of these or your own method so as I mentioned earlier when we break down glucose for energy we're going to do this in many many small tiny steps so we don't lose that much energy in the form of heat like we do when we light a match when we do this the Tiny Steps um every time energy is released we're going to capture some of that energy sometimes in the form of our high energy electron carriers like nadh so the oxidized version is nad+ and when this receives electrons it becomes nadh the reduced State and this has really high potential energy so I'll just put high potential energy this one you can see is carrying two electrons and a proton more than the NAD or oxidized state and it's called an electron carrier because nad+ accepts electrons whereas nadh will donate or has the ability to donate electrons and you can see these here these are derived from our B vitamins these are really important and we're going to see that in both this chapter cellular respiration as well as chapter 8 when we talk about photosynthesis they're going to be eventually donating or re-releasing their electrons to other molecules FES to become oxidized again and we'll see other types of electron high energy electron carriers besides nadh Throughout the chapter including fadh2 and then in chapter 8 we're going to see something called nadp+ which becomes reduced to nadph and that'll be when we talk about photosynthesis or plants and I always remember or it doesn't stand for plants it stands for phosphate but I remember P for photosynthesis or plants so I mentioned nadh nicotinamide adinin dinucleotide has high potential energy when it's in its reduced state but we don't usually use nadh to power regular body functions for example like moving our muscles or breathing or pumping your heart we do use it to generate ATP and I'll show you this at the end of the chapter today but what I like to compare nadh2 is when you go to like have you guys ever been to like dve Busters or chuckecheese when I was a kid we used to get tickets when we played these kinds of games and then we would go to the counter and trade our tickets in for prizes like a piece of candy or a toy um nowadays I think they use cards instead which is I guess more efficient but I think of nadh as these tickets they're valuable in the sense that you can trade them in for something else later on and we're going to see that this is the case for cellular respiration as well we're ultimately going to trade in our nadh for the generation of ATP so our main form of energy currency is ATP a Denine Tri phosphate and this is because when we break down our hydroly ATP into a Denine diphosphate and an inorganic phosphate and that would be cutting this Bond right here this is exergonic it relas es a good amount of energy and that energy can be used to power endergonic reactions that are not spontaneous and require energy input this loss of a phosphate group is known as def phosphorilation so if a molecule loses a phosphate group we say it's def phosphorilated the opposite if you add a phosphate group is known as phosphorilation and that's often done by enzymes called kinases so this is a generic term for enzymes that phosphorate molecules when you phosphorate a molecule it tends to be turn and become less stable and more likely to react and we saw that actually in the previous chapter when we were talking about that sodium pottassium pump remember it pushes three sodium out of the cell two potassium into the cell and uses one ATP that ATP when it's hydroly the phosphate group binds to the sodium potassium pump and increases its Affinity or more likelihood to bind to sodium and potassium when it's phosphorilated and I can see in this case uh can have I have this enzyme it's a substrate over here and it looks like a TP bonded to phosphate will generate at TP and here what I'm doing is I'm stealing a phosphate group from a substrate in order to to produce energy that I can use later on so in that picture I just showed you and also shown here is one of the methods by which we make ATP so we want ATP it's our energy currency we use it to power different types of endergonic reactions it turns out that making ATP also takes energy and that kind of makes sense because I know ATP breakdown releases energy so the production of ATP is endergonic you have to put in energy to to do this so where does this energy come from you can couple it with some kind of reaction that released energy to produce ATP and one method is known as substrate level phosphorilation this is shown here in that picture I just showed you in the previous slide as well when you literally steal a phosphate group from some other substrate and attach it to your ADP to make ATP this is called substrate level phosphorilation the second method is chemiosmosis so that first method was substrate level phosphorilation but it's not as common the most common method to produce ATP is through our second method CH osmosis which uses an enzyme ATP synthes and will be a big focus of the remainder of chapter 7 90% of our ATP is produced by CH osmosis and in UK carots this is going to happen in our mitochondria for example in animal cells human cells in Plants this also happens in the chloroplasts and in the plasma membrane for procaryotic cells since they do not have mitochondria or chloroplasts so we're going to look at the oxidation of glucose into carbon dioxide and the generation of ATP that happens during cellular respiration by looking at the different metab olic Pathways involved glycolysis will always come first regardless of the organism and then if you have oxygen available the next few steps include the oxidation of pyate which is a product of glycolysis something called the citric acid cycle and then oxidative phosphorilation so the first step of glucose catabolism or cellular respiration is glycolysis and glycolysis is what it sounds like the Lis of glucose we're going to take glucose a six carbon molecule and basically chop it in half to form two pyruvate molecules and each of these has three carbons in them oh that's an ugly three so two three carbon molecules but we're not going to do this all of a sudden we do this in many small steps and this is 10 uh different steps so that we can capture energy and make sure we lose a very small amount in the form of heat we're going to try to make this as efficient as possible the inputs include glucose some nad+ some ATP so energy is required as well as ADP and the outputs include pyrovate also known as pyic acid those high energy electron carriers nadh some ATP and some ADP so I can see this is six carbon glucose and at the end I'm going to two three carbon pyate molecules in my class you do not have to memorize every single step of each of these metabolic pathways so what I really want you to know for each of these Pathways is what goes in what are the major reactants what comes out where does it happen what are the requirements and then there will be some notable characteristics we'll describe and summarize together later on the first five steps or the first half of glycolysis actually requires an input of energy because we have to initially put in some energy we sometimes call it an investment phase and some textbooks like to call it the Preparatory phase so if I look I'm putting in glucose it looks like I need some energy in the form of ATP and one of the first steps the very first step really I see kind don't worry about the specific name but I see kinas and I remember earlier kinases are enzymes that phosphorate things they add phosphate groups to things and I see that oh wait cyas phosphorated this glucose molecule and the purpose of that is to prevent it from leaking back out of the cell you don't want to lose your glucose and lose your reactant for this reaction I see I need another ATP looks like a phosphor something else again and then it looks like I chop up the six carbon molecule in half into two three carbon molecules already the second half of glycolysis is steps 6 through 10 and it's often called the payoff phase because here is when I'm going to actually generate some ATP and overall I I'll produce a net of 2 ATP so if I look at step six and look really carefully at this figure it looks like this these steps Steps step 6 through 10 happen twice why is that the reason for this is because remember glucose was a six carbon molecule and in the first five steps of glycolysis I generated by the end of those first half of this uh the glycolysis two three carbon molecules and here they're just showing you one of those and telling you that this thing is going to happen twice I can see along the way from Step 6 through 10 I'm going to generate two of these these high energy electron carriers because this happens twice I'm going to generate a net of 2 ATP because there will be four ATP made but I used two ATP in the first half of glycolysis the method of production of ATP in glycolysis is substrate level phosphorilation the one that was not as common compared to chemiosmosis since glycolysis is is a reaction or a series of reaction that does not does not require oxygen then even anerobic cells cells that function in the presence or in the absence I should say in the absence of oxygen they can still go through glycolysis and for some cells this is the only way that they can produce ATP so let's summarize glycolysis glycolysis was when I took a six carbon glucose molecule and basically chopped it in half forming two pyruvate these three carbon molecules I produced a net of 2 ATP I produced a little bit or really two high energy electron carriers nadh and how do I regulate this so to regulate glycolysis I know that one method is by phosphor liting glucose to trap it inside of the cell as a reactant for this another way I can really regulate glycolysis and determine if it's going to happen or not is controlling the levels of nad+ if you run out of nad+ then this reaction will slow down or even stop if you have too much ATP if you have too much ATP glycolysis will also slow down so glycolysis I remember happens in the cytoplasm of cells including ukar and procaryotes and again no oxygen is necessary so it's an Anor robic reaction throughout chapter 7 in our Open Stacks textbook you'll see that you are provided with different YouTube and video links to review the different Pathways of cellular respiration these are optional you can view them but again you don't have to memorize the detailed steps of each metabolic pathway all right that takes us to the end of the first video for chapter 7 in our second video we're going to look at what happens after glycolysis