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Current time:0:00Total duration:14:19

Cellular respiration introduction

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Video transcript

in my humble opinion the single most important biochemical reaction especially to us is cellular cellular respiration and the reason why I feel so strongly about that is because this is how we derive energy from what we eat or from our fuel or if we want to be specific from glucose at the end of the day most of what we or at least carbohydrates end up is glucose in the future videos I'll talk about how we derive energy from fats or proteins but cellular respiration let's go from glucose from glucose to energy and some other byproducts and to be a little bit more specific about it let me write the chemical reaction right here so that so the chemical formula for glucose you're going to have six carbons 12 hydrogen's and six oxygens so that's your glucose right there so if you had one mole of glucose right that that's your glucose right there and then to that one mole of glucose if you had six moles of molecular oxygen running around the cell then and this is kind of a gross simplification for cellular respiration I think you're going to appreciate over the course of the next few videos that one can get as involved into this into this mechanism as possible I think it's nice to get the big picture but if you give me some glucose if you have one mole of glucose and six moles of oxygen through the process of cellular respiration and so I'm just writing it it's kind of a big black box right now let me pick a nice color so this is cellular cellular respiration which we'll see is quite involved but I guess anything can be if you want to be particular about it through cellular respiration we're going to produce six moles of carbon dioxide six moles of water and and this is the key this is the the super important part and we're going to produce energy we're going to produce energy and this is the energy that we're going to that that can be used to to a useful work to put to heat our bodies to to provide electrical impulses in our brains whatever whatever energy of especially human body needs but it's not just humans it's provided by this cellular respiration mechanism and when you same energy you might say hey Sal you know in the last video didn't you just well if you if that was the last video you watched you probably saw that I said that ATP ATP is the energy currency is the energy currency for biological systems and so you might say hey well looks like glucose is the energy currency for biological systems and to some degree both both answers would be correct but to just see how it kind of fits together is that the process of cellular respiration it does produce energy directly but that energy is used to produce ATP so if I were to break down this energy portion of cellular respiration right there some of it would just be heat you know it just warms up the cell and then some of it is used and this is what the textbooks will tell you the textbooks will say it produces 38 ATP's that can be more readily used by cells to contract muscles or to generate nerve impulses or do whatever else or grow or divide or whatever else the cell might need so really cellular respiration to say it produces energy little disingenuous it's really the process of taking glucose and producing ATP's with maybe heat as a by-product but it's probably nice to have that heat around we need we need we need to be reasonably warm in order for our cells to operate correctly so the whole point is really to go from glucose from one mole of glucose and the textbooks will tell you to 38 ATP's and the reality is this is in kind of the ideal circumstances that you'll produce 38 ATP's I was reading up about it a little bit before doing this video and the reality is depending on the efficiency of the cell and performing cellular respiration it'll probably be more on the order of 29 to 30 ATP's but there's huge variation here and people are are really still studying this idea but this is all cellular operation is in the next few videos we're going to break it down into its kind of constituent parts and I'm going to introduce them to you right now just so you kind of realize that these are parts of cellular respiration the first stage is called glycolysis glycolysis which literally means breaking up glucose and just so you know this is part you know this the gly for glucose and or the glyco for glucose really the glyco for glucose and then lysis means to break up when you saw hydrolysis it means using water to break up a molecule glycolysis this means we're going to be breaking up glucose and in case you care about things like word origins glucose comes from the glue the glue cart of glucose comes for Greek for sweet and glucose is indeed sweet and then all sugars we put this O's ending so that just means sugar so you might think it's kind of a redundant statement to say sweet sugar but there are some sugars that aren't sweet for example lactose and you know milk it might be a little bit but you know when you actually when you actually digest lactose and you can turn it into an actual sweet sugar but it doesn't taste sweet like glucose or fructose with actual or sucrose would taste but anyway that's a that's an aside but the first step of cellular respiration is glycolysis breaking up of glucose and what it does is it breaks up the glucose from a six carbon from a six carbon molecule so it literally takes it from a six carbon molecule we draw it like this a six carbon molecule that looks like this and it's actually a cycle let me show you what glucose actually looks like this is glucose right here and notice you have one two three four five six carbons I got this off of Wikipedia just look up glucose and you can see this diagram if you want to kind of see the details where you know you can see I have six carbons six oxygens that's one two three four five six and then all of these little small blue things are my hydrogen so that's what glucose actually looks like but the process of glycolysis you're essentially just taking that I'm writing it out as a kind of a string but can imagine it as a chain and it has oxygens and hydrogen's added to it to each of these carbons but that has a carbon backbone and it breaks that carbon back groans into into two that's what glycolysis does right there so you kind of lysed the glucose and each of these things and I haven't drawn all the other stuff that's added on to that you know these things are all bonded with other things with oxygens and hydrogen's whatever but each of these three carbon backbone molecules are called pyruvate we'll go into a lot more detail on that but by glycolysis it generates it by itself generates well it needs two ATP's so it needs two ATP's and it generates generates four ATP's so net net on a net basis it generates two let me write this in a different color it generates two net two net ATP so that's the first age and this this can occur completely in the absence of oxygen I'll do a whole video on glycolysis in the future then these byproducts they get re-engineered a little bit and then they enter into what's called the Krebs cycle they enter what's called the Krebs krebs cycle which generates another two ATP and then and this is the this is kind of the interesting point there's another process that you can kind of say happens after the Krebs cycle but we're in a cell and everything is bumping into everything all of the time but it's normally kind of viewed to be after glycolysis and the Krebs cycle and this requires let me make this requires oxygen requires oxygen so let me be clear glycolysis this first step no oxygen required or doesn't need oxygen oxygen it can occur with oxygen or without it oxygen not needed oxygen not needed or you could say this is called an anaerobic process this is you know this is the anaerobic part the respiration let me write that down to anaerobic maybe I'll write it down here glycolysis glycolysis since it doesn't need oxygen we can say it's anaerobic you might be familiar with the idea of aerobic exercise the whole idea of aerobic exercise is to make you breathe hard because you need a lot of oxygen to do aerobic exercises so anaerobic means you don't need oxygen aerobic means it needs oxygen anaerobic means the opposite you don't need oxygen so glycolysis anaerobic and it produces two ATP's net and then you go to the Krebs cycle then you go to the Krebs cycle there's a little bit of setup involved here and we'll do the detail on that in the future but then you move over to the Krebs cycle which is aerobic it is aerobic it requires oxygen to be around and then this produces two ATP's and then this is the part that frankly when I first learned it confused me a lot but I'll just write it in order the way it's traditionally rote then you have something called reusing the same colors too much you have something called the electron transport chain electron transport chain and this part gets credit for producing the bulk of the ATP's 34 ATP's and this is also aerobic it requires oxygen so you can see with if you had no oxygen if you weren't if the cells weren't getting enough oxygen you can produce a little bit of energy but if you don't but it's nowhere near as much as you can produce once you have the oxygen and actually when you're when you start running out of oxygen you know this can't proceed forward so what happens is some of these byproducts of glycolysis instead of going into the Krebs cycle and the electron transport chain where they need oxygen instead they go through a side process called fermentation fermentation for some organisms this process of fermentation takes your byproducts of glycolysis and literally produces alcohol that's where alcohol comes from that's called alcohol fermentation and we as human beings I guess fortunately or unfortunately our muscles do not directly produce alcohol they produce lactic acid so we probably do lactic acid fermentation write that down lactic acid that's humans and probably other mammals humans but other things like yeast will do so yeast will do alcohol form fermentation alcohol alcohol fermentation so this is when you don't have oxygen it's actually this lactic acid that if I were to you know sprint really hard and not be able to get enough oxygen that my muscles start to ache because this lactic acid starts to build up but that's just a side thing if we have oxygen we can move to the krebs cycle get our two ATP's and then go on to the electron transport chain and produce 34 ATP's which is really the bulk of what happens in respiration now I kind of said this as an aside that you know to some degree this isn't fair because while these guys are operating they're also producing these other molecules or let me they're not producing them entirely but what they're doing is they're taking I know it gets complicated here but I think over the course of the next few videos we'll get an intuition for it in these two parts of the reaction glycolysis and the Krebs cycle we're constantly taking nad alright as nad plus and we're adding hydrogen's to it to form NADH and this actually happens for ten for one molecule of glucose this happens to ten nad s or ten nad plus is to become NADH s and those are actually what drive the electron transport chain and I'll talk a lot more about it and kind of how that happens and why is energy being derived and and how is this an oxidative reaction and all of that and you know what's getting oxidized in what's being reduced but I just wanted to give due credit these guys aren't just producing two atps in each each of these stages they're also producing actually combined ten nadh --is which are then use which each which each produce three ATP's in an ideal situation the electron transport chain and they're also doing it this other molecule FA D which is very similar but they're producing FA F eh now I know all of this is very complicated I'll make videos on this in the future but the important thing to remember is cellular respiration all it is is taking glucose and kind of repackaging the energy and glucose and repackaging it in the form of your textbooks will tell you 38 ATP's and if taking the exam that's a good number to write it tends to in reality be a smaller number it's also going to produce heat actually most of it is going to be heat but 38 ATP's and it does it through three stages the first stage is glycolysis where you're just literally splitting splitting the glucose into two you're generating some ATP's but the more important thing is you're generating some NADH s that are going to be used later in the electron transport chain then those byproducts are split even more in the Krebs cycle directly producing two atps but that produces a lot more NADH s and then all of those NADH s are used in the electron transport chain to produce the bulk of your of your energy currency or your 34 ATP's