Hi. So in this video, we're going to be going on an overview of aerobic respiration. The first thing I want to talk about is cellular respiration, which is the series of reactions that involve electron transfers, which break down molecules for energy. Cellular respiration breaks down molecules for energy and, in the process, does a lot of electron transferring. During fermentation, when it's oxidized, it loses its electrons and creates a molecule known as acetyl CoA. The acetyl CoA is processed by a cycle called the tricarboxylic acid cycle. You may see it as the Krebs cycle or the citric acid cycle. I don't know why it needs three names, but it definitely has them. Acetyl CoA oxidizes to create carbon dioxide. In the process of this, there's a lot of electrons being carried by electron carriers. Eventually, these electrons are transferred through what's known as the electron transfer chain, which will eventually be used to produce ATP synthesis. We've gone over a few of these; we're going to go over more in greater detail with the exact steps of what they do, but this is just an overview of cellular respiration.
Let me step back a bit. First, we have glycolysis. This occurs in the cytoplasm. Remember, you don't need to know these steps if you've already reviewed them, but eventually, this creates pyruvate. This pyruvate can then be converted into Acetyl CoA, which cycles through the Krebs Cycle or the citric acid cycle. This creates a bunch of NADH, CO2, FADH2, and ATP. These electron carriers eventually travel through the electron transport chain, and you can see that they end up pumping a lot of hydrogens which can then be used to create ATP. This is just an overview. Realize there are a lot of little tiny details in these images. You don't need to know these little details or how many NADHs, at least not yet. But just get an idea that all these different processes are connected in these five steps that you went over, and those connections end up creating energy. With that, let's now move on to the next page and talk about oxidative phosphorylation.
Oxidative phosphorylation describes a series of reactions that oxidize molecules and use electrical energy to generate ATP. This involves what is known as chemiosmotic coupling, which means that a proton gradient, which is electrochemical, meaning there's an electrical charge and a concentration gradient of hydrogen protons, couples that gradient with the creation of ATP. In stage 1, the electron transport chain, which we remember from above is going to be step 4, pumps a bunch of hydrogens across the membrane, creating this gradient. Then, in stage 2, there is ATP synthesis because that gradient can flow back down across the membrane, and that energy is used to create ATP. The proton motive force, or the hydrogen electrochemical gradient, is what drives ATP synthesis. So, let me step away again, and we'll look at this example of an electron transport chain in plants because you can see it in chloroplasts and thylakoids. You don't necessarily need to know that now, but essentially what happens is there are all these processes that the electrons are transferred to throughout an entire process. Eventually, you can see that there's a bunch of hydrogens getting pumped into the cell, and you get this hydrogen electrochemical gradient that is eventually used to create ATP from ADP. So, that's an overview of cellular respiration and oxidative phosphorylation. With that, let's now move on.
