 Let's learn all the phases of the cellular respiration. The first is glycolysis. Glycolysis is, just as the words say, it's breaking down the sugar, lysis is breaking and glyco mean sugar. So glucose, the molecule that our brain can digest, the only monosaccharide that our brain actually can utilize, is is one of the major energy molecules in our body and let's see what's going on with that molecule. Glycolysis is happening in the cytoplasm, okay? And the most important thing to remember is that pyrobat, a three carbon molecule, is the one that is a result in the process of glycolysis. Now, in the beginning of the glycolysis process, we actually first need to spend, that is called investment phase, to spend two ATP molecules. So ATP is utilized to make glucose or 6-phosphate which means that the phosphate group is attached to the glucose in order to energize it, in order to continue the process. Now, overall four ATPs are produced, but considering that we have spent two of the ATPs to start the process, as an end result, we harvested two ATP molecules. Now, in the process of making pyrobat, what is released is NADH as well. NADH is going to be utilized in the final form of, in the final process of the cell respiration, so we'll talk a little bit more about it later. The pyrobat is the one that is utilized also to bring back to make glucose. In the case that we are not taking enough glucose, pyrobat molecule can be made in our, it can be utilized in our liver to be converted back to glucose. And in our liver, the polymer that is our energy depot, so to speak, is lycogen. Lycogen is the polymer of glucose. So here you can see that it's series of nine reactions. Of course, if we were just to make glucose to pyrobat, it will be pretty much a positive reaction, so that is not happening. Glycolysis can happen whether the oxygen is present or not. We will learn more about it, what's happening when the oxygen is not present. However, pyrobat has three carbon molecules, three carbon atoms, and this molecule is losing one of the carbon atoms before it enters the matrix in the mitochondria. So that is called decarboxylation process and the pyrobat enters the process as acetyl-coenzyme A that has only two carbon atoms in it. During this process, one NADH is produced as well. And you can see here where is, what is the acetyl-coenzyme A? Pyrobat, again, very important, pyrobat. Decarboxylation process taking away one carbon atom with utilization of the coenzyme A, coenzyme A has sulfur group. This is the entry point for the next step. If you notice here, glucose that has six carbons is breaking down and two pyrobat molecules are here. So for every cell respiration cycle for one molecule of glucose, we have two cycles that are entered by pyrobat. That would be the most important about glycolysis.