 first the contents, crab cycle, breakdown of carbon skeleton, reduction of electron carriers, location of crab cycle, formation of acetyl coenzyme A, and formation of citric acid. So first the crab cycle. So crab cycle come crab cycle is like a hand scrap was the scientist who first discovered this cycle within the cells. In the cells, first of all this metabolic pathway was discovered by the hands crab. In the same name we call it crab cycle. So we define the definition of crab cycle. So crab cycle is basically a cyclic metabolic pathway in which acetyl coenzyme A reacts with the oxaloacetate and it produced the carbon dioxide molecules are complete carbon skeleton of glucose is broken down that is converted into the carbon dioxide. Similarly acetyl coenzyme A, because if we see acetyl coenzyme A is basically made from pyruvate. Then from glucose pyruvate, pyruvate acetyl coenzyme A, acetyl coenzyme A enters the crab cycle and after that all the carbon atoms convert into all the carbon dioxide. So we also call the crab cycle citric acid cycle. In addition, the crab cycle is called tricarboxylic acid cycle. Citric acid cycle is the first reaction in the crab cycle. When the oxaloacetate and acetyl coenzyme A are found, then citric acid is formed. That is why we call it citric acid cycle. And tricarboxylic acid cycle is called three carboxylic groups of citric acid. So the first molecule is the carboxylic group CWH group. So because of the three carboxylic groups, we call it tricarboxylic acid cycle. Then we have the sequence of the crab cycle. From glucose pyruvate, pyruvate acetyl coenzyme A. And acetyl coenzyme A is the crab cycle. One thing you have to keep in mind is that in some books it is written that in the crab cycle, pyruvate is entering the crab cycle. No, pyruvate first converted into acetyl coenzyme A. Then acetyl coenzyme A will join the crab cycle. If we look at the crab cycle, then the carbon skeleton of the glucose will completely break or oxidize. So the complete oxidation will become the carbon skeleton of the glucose. If we look at the sequence, when the glucose enters the glycolysis, the glucose has six carbons. When the glycolysis ends, the six carbons are made into two molecules of three three carbons. It is called pyruvate. As soon as the pyruvate becomes acetyl coenzyme A, one carbon will be converted into carbon dioxide. So one of the three carbons converted into carbon dioxide. Two carbons will enter the crab cycle. These two carbons convert into carbon dioxide in different steps of the crab cycle. This is the same process in one pyruvate. All the carbon atoms of the glucose are converted into carbon dioxide. It is called glucose is completely oxidized during the crab cycle. Overall, if you look at the steps written, there are two pyruvates of one glucose, two pyruvates of two acetyl coenzymes, and two carbon dioxide. Similarly, when the two acetyl coenzymes enter the crab cycle, one acetyl will turn into two acetyl groups of four carbons. So total six carbons and six carbon dioxide molecules will be released. What is happening else in the crab cycle? What is happening in the crab cycle? In the crab cycle, apart from becoming carbon dioxide gas, apart from the degradation of carbon skeleton, the important thing is the synthesis of the reduced electron carrier. The electron carrier is the synthesis of NADH and FADH2. During one crab cycle, three NADH will be produced and one FADH2 will be produced. Now look, if there were two pyruvates, then the crab cycle would work. In one crab cycle, three NADH plus one FADH2. In the second crab cycle, again three NADH plus one FADH2. So when two pyruvates of two molecules of the total glucose cycle, three plus three will become six NADH and two FADH2 will be produced. One extra thing is one. One GTP molecule is also produced during the crab cycle. GTP is equivalent to ATP. There are some cells of our body, especially protein synthesis. Protein synthesis is used during the GTP. GTP is also the energy currency of the cell. This will also be used as a cell energy currency. What is the location of the crab cycle? In the crab cycle, we are very clear that the crab cycle is in cytoplasm. It is in the cytoplasm. The crab cycle always takes place in the mitochondria. So the crab cycle will be in the mitochondria. This means that if the pyruvate is formed through glycosac, it is formed in cytoplasm, in the cytoplasm. The crab cycle is in the mitochondria. Then the pyruvate has to be moved into the mitochondria. This is the step in which the pyruvate has to be moved into the mitochondria. This is the step in which the pyruvate has to be moved into the mitochondria. Now, when the pyruvate comes into the mitochondria, the pyruvate will not be directly a part of the crab cycle. The first step is the decarboxylation step. This means that the pyruvate is converted into acetylcoenzyme A. Along with it, there will be a reduction in NADH molecules. The decarboxylation step is called pyruvate is converted into acetylcoenzyme A. One molecule of the carbon dioxide is released, and one molecule of NADH is also synthesized here. If you look at the reaction here, this is the step in which the pyruvate is converted into acetylcoenzyme A. So first of all, if you look at it from the board, the pyruc-c-double-h group, the carboxylic group is released in the form of carbon dioxide. So from the pyruvate, from the three-carbon-pyruvate, we have two carbons being converted into acetylcoenzyme A. One molecule of the carbon dioxide is released, and one NADH is synthesized. Formation of citric acid. The citric acid cycle here will start. Now, the acetylcoenzyme A is synthesized, and the formation is that it will be combined with oxaloacetate in a mitochondria. It is also called oxaloacetic acid. What is oxaloacetic acid? What is oxaloacetate? When you combine oxaloacetic acid with acetylcoenzyme A, oxaloacetic acid is a four-carbon molecule. Acetylcoenzyme A is a two-carbon molecule. So when you combine four-carbon and two-carbon, it will be a six-carbon molecule. That is the citric acid. The citric acid is a six-carbon molecule. And interestingly, if we look at it, the first molecule that is formed is citric acid. That is why we call the Crab Cycle as citric acid cycle. With the citric acid cycle, there are three carboxylic groups, CWH groups, and that is why we call it tricarboxylic acid cycle. The three CWH groups, which are called tricarboxylic acid cycles, are called tricarboxylic acid cycles.