Hi in this video we're gonna be talking about the breakdown and utilization of sugars. So first let's overview metabolism. So we know about metabolism because you've talked about it before in your intro classes, but metabolism is just going to be just defined as the sum of all chemical reactions in a cell. And so there are different reactions that happen um that make up metabolism. So the first thing we're gonna talk about is metabolism and that's going to be all reactions that break down something. So break down macro molecules. These are generally going to be energetically favorable because it's easier to break down stuff than it is to form things. Um And because the energy is released from the bonds. So the second form that we want to talk about is anabel is um and that's going to be the opposite. So those are reactions that synthesize or form macro molecules. And these are gonna be unfavorable reactions because you have to put energy in in order to be able to create new macro molecules. And so finally, the last term that I really want to review in this video is gonna be metabolic pathways and what those are. Those are going to be a series of reactions where the the product of one is the substrate for the next. So you can kind of imagine these is just like lines. So you have you can sometimes see these before where you have some type of reaction and it forms a product and that's used to form another product. And so this is gonna be a metabolic pathway where the product of one reaction is gonna be the starting material for the next one. And so um another term associated with this is called metabolites. And those or metabolic intermediates which you may see. And these are gonna be compounds that are formed in the process of creating the end product. So different like chemicals are different products that can all be metabolites. These are things that are made in the process of creating something else, some kind of end product. So as a review of um the different forms of metabolism, we have a metabolism here which is going to be breaking apart something and then we have anabel is um which is gonna be forming something. So you can see there's all these individual pieces and it gets formed and that a nationalism or metabolism releases energy. But a naturalism uses energy. And so um that's that's the difference in a review of metabolism. So now let's move on.

So in this video we're gonna be talking specifically about glucose and how it's important in getting energy to the cell. So in order to survive cells have to get energy from fuel molecules. And what I mean by fuel is usually some type of food doesn't have to be can be light for instance but energy has to be obtained from somewhere. And so the first one that I want to talk about is cell respiration. And that's going to be the process of harvesting energy from bonds and sugar molecules. And this is really important, especially for animal cells in order to get the energy that they need to survive. So glucose is actually the most important sugar for respiration. And the reason is because it carries all this energy. So if you remember back to the delta G. Um that we talked about I think way long time ago if you don't it's fine you don't need to know this number. But if you do, the delta G of glucose is negative 6 86 kilocalories per mole, which is a huge negative number. Which means that it's really energetically favorable to break it apart. So the breakdown of sugars, things like clothes is energetically favorable and generally the cell likes to couple this breakdown with the creation of other forms of energy. So usually this energy formation is A T. P. So normally in the cell the creation of a T. P. Is real hard. It's not easy. It requires a lot of energy and so it's not that favorable of reaction. So what cells do to overcome that is they take sugar molecules that are really easily broken down and they take that energy to form more usable energy in the form of A. T. P. And so because they want to couple these reactions to the breakdown of sugar and the formation of other usable energy. The gate ep the process has to be really controlled. And so the reason it has to is because it needs to be harvested and tiny steps a little by little so that the energy can all be taken up by other molecules instead of just kind of like exploding on something that's not really able to handle that much energy in one go. So metabolism and cellular respiration is the breakdown of sugars is a really controlled process to harvest the energy from sugars to create usable forms of energy like a teepee. So if we just look here at this formula, you don't need to memorize this formula. Especially not right this second, you may need to in the future but not right now. But essentially what this means is you take glucose here and respiration occurs with things like oxygen which we're familiar with animals, you know, animals need oxygen. Um So they had glucose and oxygen undergo respiration to create some waste products co two water but most importantly it couples this reaction with the formation of A T. P. So the breakdown of glucose releases energy which is then used in this reaction to create a teepee. It's really, really important process so that let's now move on.

So in this video we're going to focus on the three stages of metabolism, which if you remember what metabolism is, that is going to be the breakdown of macro molecules. Um and so specifically what we're going to talk about is, you know, the three stages of breaking down food. So usually sugar molecules of some kind. So the first thing that happens after you eat a meal, you digest it. So there's digestion. So you take your pizza and your stomach can break that down into larger molecules of smaller subunits. So pizza is made up of lots of complex molecules and sugars and carbohydrates and your stomach. And in the process of digestion will break those really large molecules into smaller subunits. And so this can occur both what I was talking about outside the cells in the stomach or in the intestine, but it also concur inside cells if the molecules can get in and that will really happen in license zones, because the license zone can also acts kind of as the stomach of the cell. To break apart these really big molecules. So once the molecules are broken into individual subunits, it's useful. But we still can't really use those sub units for anything, They have to be, the energy needs to be taken out of them. So what happens next is a step process called glycol Asus and this is going to break down glucose or other sugar molecules. So these monitors or sub units into a chemical called piru. And um during this process which occurs in the side of saul. So now we're inside sales 100% of the time in the side of Saul. Um In the process of this changing the sugar molecule into Piru what the cell does, it actually can generate things like a DP um This molecule called N A. D. H, which is an electron carrier um and pyro bait. Um and then eventually Piru bay is used by the cell to turn into carbon dioxide as well as this other molecule that we're going to talk a lot about Placido Coetzee, which is an activated carrier. Which do you remember what an activated carrier is? Right. So that's gonna be a molecule that can carry electrons and electron carrying is really important because that allows us to carry these electrons that have high energy from one reaction or one area of the cell to another to have some other type of reaction occur. So now we've eaten our pizza. It's been digested that those sugars have been broken down through glycol Asus. And so now we have some 80 P. Some N A. D. H. And maybe some C. 02 acetyl coa A. And so then what then the next thing that happened is oxidative phosphor relation and this is the metabolic pathway that leads to the largest production of A. T. P. So this is really where we get our usable energy from. And so now we have moved into the mitochondria. So we're still in the south but no longer in the side is all. And this is a process that creates C 02 N A T H A T P. And also citrate, which is for another cycle that we're going to talk about called the citric acid cycle. Um but this is the cycle called oxidative possible relation because it consumes oxygen. So this is where the oxygen that we breathe in goes to. For the most part now we are going to go over each one of the, well we're not going to go our digestion but we're gonna go over like palaces oxidative phosphor relation in the citric acid cycle in really great detail. So if you don't necessarily want to memorize, oh by policies that all this, you know, creates power but yet that's fine but we will need to memorize this in the future. So be prepared for that. So this is an image here. I'm just looking at different types of metabolic pathways and it's really complicated. And I don't want you to remember these steps or anything. So just sort of step back and look at this just as an image and let me walk you through it. So what we can see here is um first is that we're sort of in the in the cytoplasm here in this area is gonna be the mitochondria. So you can see some of the steps that I talked about, you have like Alice is here which is going to occur in the cytoplasm and it's going to create some 80 P. Some N A. D. H. Um And then this travels through here to the mitochondria where the citric acid cycle which sometimes called the Krebs cycle or the T. C. A cycle occurs. And then you have oxidative false correlation occurring and um all of this is happening. Um And it's creating a teepee in various ways. It's creating proton gradients, it's creating electron carriers. Um It's creating all these different molecules and we're going to go through the steps of all of them. But you can just sort of understand that the process of this breakdown of sugar molecules is not necessarily that easy. It's really complex and involves a lot of steps but I'm gonna walk you through them. So with that let's now turn the page.

So in this video, I'm going to focus on the importance of oxygen and this breakdown process of sugars. And so the presence of oxygen actually dictates which metabolic pathway the cell will use to break down sugars are light or whatever it's going to break down for energy. And so that there are really two types of respiration completely dependent on whether oxygen is available. So if oxygen is not available, it's called anaerobic respirations of no oxygen or it's called aerobic respiration with oxygen. And you can kind of think of that as like aerobic air has oxygen whereas anaerobic has no oxygen. And so aerobic respiration you can imagine especially in animal cells has a really high energy yields much higher than that anaerobic respiration. So generally the cell is going to prefer to use aerobic respiration, but it can only do that if oxygen is available. And sometimes especially in some cells you think like in your muscles during a workout, oxygen isn't always available and enough levels to do that for energy. So organisms are based on our names are classified based on their requirement for oxygen during metabolism. So obligate Arabs have an absolute requirement for oxygen. So these are humans, humans cannot survive without oxygen because our cells can't break down energy breakdown food molecules for energy without oxygen. So we have to have it. So we are this class. But you have some other organisms that um called obligate anaerobic and these are molecules that are organisms that cannot in any under circumstance use oxygen and oxygen will actually potentially be toxic to them. So you can I kind of think of these as those weird organisms you hear living at hydrothermal vents are way down in the ocean. Sometimes that's these organisms here who not only don't use oxygen but it actually might be toxic to them if they are exposed to it. And then you have calculated organisms and these can function with or without oxygen and can switch between the two forms when there's oxygen available or when there's not. And so this mainly classifies the bacteria. So um here we have a variety of different metabolic pathway starting from the sugar of choice which is gonna be glucose. And you can see that in the cell, glucose is going to be going under go go through like a colossus which is going to turn it into piru. Now the presence of oxygen sort of depends on what primary bait does. So if oxygen is not president then the cell uses that probate to undergo a process called fermentation which we haven't mentioned yet. You probably heard about it. You know is used a great beer and stuff like that. But fermentation is done without oxygen but it doesn't create a lot of energy. Alternatively if oxygen is present then the cell can use all these other pathways oxidative or oxidative things. Krebs cycles, electron transport chain. You don't necessarily know all these yet we're gonna go over them individually but it creates a lot of ADP per every starting molecule of glucose. And so this is gonna be the preferred pathway. But it can only happen if oxygen is present. So with that let's now turn the page.