So the topic today of our discussion is cellular respiration. I've drawn for you here out the equation, the overall equation for cellular respiration, and so let's look at it for just a second. What we see is this is one molecule of glucose in the presence of oxygen yields water, carbon dioxide, and ATP, which is the energy currency for the cell. Now, we know from previous lessons that all cells require ATP to carry out their cellular work. Therefore, if cells don't have ATP, they're going to die. So this reaction shows you how your cells in your body are actually producing the ATP that they need in order to function. Now, I want to point out a couple of things to you, and first of all, we have oxygen gas, and we have carbon dioxide, and you already know that you breathe in oxygen gas, and then you exhale carbon dioxide. This reaction is why you must have a supply of oxygen, and you have a waste of carbon dioxide that

you have to breathe out. In order for cells to do this process, they have to have a continuous supply of oxygen, which you supply by breathing. And then the waste gas, carbon dioxide, is what you're exhaling. So now you see why you actually need to breathe, because your cells need to continue to produce ATP to stay healthy. Now, the other thing I want to talk about is this molecule right here, glucose. And we know something about glucose. We know this is a sugar, and therefore we know it's in a lot of the food that we eat. Even starch, we know is broken down into individual glucose molecules. So this is by ingesting and digesting food. This is one of the nutrients that your digestive system breaks down. Now, obviously, we eat more than just sugar. We eat fats and we eat proteins. So glucose is not our only energy source. But for this lesson, we're going to follow one molecule of glucose until it's

completely oxidized or broken down into carbon dioxide to show how the cell generates energy. Now, at the end, I'm going to show you that no matter whether you're ingesting fats or proteins or other sugars, they all get broken down in a similar process to produce energy for the cell. But for now, we're just going to track through one molecule of glucose to see how the energy is produced. Now, the other thing I want to point out to you is this glucose molecule. It does have energy, OK, stored in the chemical bonds. So in other words, there are bonds between those carbons and the carbons and hydrogen and oxygen. Those bonds themselves are potential energy. Therefore, this process is essentially the slow breakdown or oxidation of the bonds of glucose. As those bonds are broken, energy is released, and that energy is used to generate ATP molecules, and that's what the cell uses to do with cellular work. So let's talk a little bit now about something.

called a redox reaction in a cell. This process is a redox reaction, as well as the next lesson that you'll talk about next week, which is photosynthesis, is also a redox reaction. Now, what do I mean by Redox? Well, something can be reduced chemically, and something can be oxidized. A reduction just simply means the gain of electrons. Oxidation means the loss of electrons. Now we know that bonds, chemical bonds, are made up of electrons. So when we break bonds, we can have the transfer of electrons from one molecule to another. Now, for us in this particular equation, to make it easier to follow what's happening with the electrons, we can also say gaining a hydrogen or losing a hydrogen, because we're not talking about a hydrogen ion, we're talking about hydrogen that carries with it an electron. So by gaining a hydrogen, we can say that that's gaining an electron, and vice versa. Losing a hydrogen would be losing an electron. So

we want to find out which of these so on this side of the arrow over here [left side] are the reactants, and on this side of the arrow [right] are the products. We first want to find out which one of these reactants is being oxidized and which one is being reduced because when one molecule is gaining electrons, those electrons had to come from somewhere. Right. So therefore, another molecule had to lose electrons. And that's why we call this a redox reaction because we have both occurring a reduction and an oxidation. Let's start with glucose. Glucose is our only carbon-containing compound on the reactant side, and therefore we realize that it is being converted into carbon dioxide because that's the only carbon-containing compound on the product side. So we start with glucose, which has 12 hydrogens. We end up with carbon dioxide, which has no hydrogen. So we can say, all right, we have a loss of hydrogens.

which means we have a loss of electrons. This tells me this is the oxidation reaction. Glucose is being oxidized into carbon dioxide. Oxygen is our other reactant. OK, and it is being converted into water. Oxygen has no hydrogen's, but water has several. So we say, well, we have a gain of hydrogen's or a gain of electrons. Therefore, this shows that oxygen is being reduced into water. Before we move on, so I'm going to have a separate video for you for each of the main processes of cellular respiration. So this one reaction is actually we're going to break it down into three different process to show in detail how this actually is carried out in the cell. And so the first process we're going to talk about is called glycolysis. OK? And this occurs in the cytoplasm of the cell, not the mitochondria. The next process is called the Krebs cycle. Or

sometimes it's referred to as the citric acid cycle, so those are the same thing. This is occurring in the mitochondria. And the third process is called the electron transport chain. And this is important because a process called Oxidative phosphorylation is carried out here. We'll talk about that in detail when we talk about the electron transport chain. This is also carried out in the mitochondria. So. You'll need to watch each successive video about the Glycolysis, Krebs cycle, electron transport chain to get the details of this cellular respiration process.

Cellular Respiration

Cellular Respiration