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The citric acid cycle is the process that occurs during cellular respiration after the cell has successfully completed glycolysis and after the pyruvate has gone through the pyruvate dehydrogenase complex, where the end product was the Acetyl-CoA. This molecule is now going to be oxidized to CO2, by the series of reactions in the citric acid cycle. During the citric acid cycle, the cell makes some ATP, GTP and some electron carriers: NADH and FADH2. These electron carriers are later going to be utilized in the electron transport chain, to make more energy. The citric acid cycle takes place in the mitochondrial matrix.
The steps of the citric acid cycle:
1. Oxaloacetate is joined together with Acetyl-CoA, forming citrate. One water molecule is consumed, and the CoA is kicked off. The enzyme that is used here to catalyze the reaction is called citrate synthase.
2. Citrate is isomerized to form isocitrate. The enzyme that catalyzes this reaction is called aconitase.
3. Isocitrate is oxidized to form alpha-ketoglutarate. During this reaction, an NAD+ is reduced to form NADH, and carbondioxide is also released. The enzyme that plays the crucial role here is the isocitrate dehydrogenase
4. Thanks to the alphaketoglutarate dehydrogenase, the alpha-ketoglutarate becomes succinyl CoA. An NAD+ gets reduced and forms NADH, the CoA is joined to the molecule and CO2 is released.
5. Succinyl-CoA is now converted to succinate. The CoA is kicked off, and one GDP gets reduced to form GTP. An ADP comes in and takes the phosphate group from the GTP, so that it can become ATP. The enzyme that catalyzes this reaction is called succinyl-CoA synthetase. It has this name because the reaction is reversable.
6. The succinate is oxidized into fumarate. Two of the hydrogen atoms in the succinate are kicked off and picked up by the FAD. This way, the FAD is reduced to form FADH2, which is later going to be utilized in the electron transport chain. The enzyme that removes these hydrogens from th succinate is called succinate dehydrogenase.
7. Fumarase reduces fumarate to form malate. The way it does that is that it joins one water molecule to the fumarate.
8. Lastly, malate dehydrogenase removes hydrogens from the malate. Thus, malate is converted back to oxaloacetate, the molecule we started with. The hydrogens are picked up by the electron carriers.
The citric acid cycle is the process that occurs during cellular respiration after the cell has successfully completed glycolysis and after the pyruvate has gone through the pyruvate dehydrogenase complex, where the end product was the Acetyl-CoA. This molecule is now going to be oxidized to CO2, by the series of reactions in the citric acid cycle. During the citric acid cycle, the cell makes some ATP, GTP and some electron carriers: NADH and FADH2. These electron carriers are later going to be utilized in the electron transport chain, to make more energy. The citric acid cycle takes place in the mitochondrial matrix.
The steps of the citric acid cycle:
1. Oxaloacetate is joined together with Acetyl-CoA, forming citrate. One water molecule is consumed, and the CoA is kicked off. The enzyme that is used here to catalyze the reaction is called citrate synthase.
2. Citrate is isomerized to form isocitrate. The enzyme that catalyzes this reaction is called aconitase.
3. Isocitrate is oxidized to form alpha-ketoglutarate. During this reaction, an NAD+ is reduced to form NADH, and carbondioxide is also released. The enzyme that plays the crucial role here is the isocitrate dehydrogenase
4. Thanks to the alphaketoglutarate dehydrogenase, the alpha-ketoglutarate becomes succinyl CoA. An NAD+ gets reduced and forms NADH, the CoA is joined to the molecule and CO2 is released.
5. Succinyl-CoA is now converted to succinate. The CoA is kicked off, and one GDP gets reduced to form GTP. An ADP comes in and takes the phosphate group from the GTP, so that it can become ATP. The enzyme that catalyzes this reaction is called succinyl-CoA synthetase. It has this name because the reaction is reversable.
6. The succinate is oxidized into fumarate. Two of the hydrogen atoms in the succinate are kicked off and picked up by the FAD. This way, the FAD is reduced to form FADH2, which is later going to be utilized in the electron transport chain. The enzyme that removes these hydrogens from th succinate is called succinate dehydrogenase.
7. Fumarase reduces fumarate to form malate. The way it does that is that it joins one water molecule to the fumarate.
8. Lastly, malate dehydrogenase removes hydrogens from the malate. Thus, malate is converted back to oxaloacetate, the molecule we started with. The hydrogens are picked up by the electron carriers.
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