BCH-5 Citric Acid Cycle

BCH-5 Citric Acid Cycle - Citric Acid Cycle Citric Acid...

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Unformatted text preview: Citric Acid Cycle Citric Acid Cycle The citric acid cycle operates in the mitochondrion of plant and animal cells. You can also find the same enzymes in certain bacterial cells. Carbohydrates, amino acids and fatty acids are fed into the cycle and will be oxidized to carbon dioxide and water. The first step of the cycle, acetyl-CoA combines with oxaloacetate to form citric acid. Each turn of the cycle releases two molecules of CO 2 , regenerates oxaloacetate, and delivers reducing agents to the electron transport chain. The citric acid cycle serves as the hub of metabolic pathways, serving to connect the breakdown and synthesis of proteins, carbohydrates and lipids. The citric acid cycle is amphibolic. A great deal of usable energy (ATP) can be produced through the aerobic oxidation of organic matter. This couples the citric acid cycle via electron ansport to oxidative phosphorylation. transport to oxidative phosphorylation. What is the Overall Pathway? – In eukaryotes, glycolysis occurs in the cytosol, while the citric acid cycle takes place in the mitochondria. Most of the enzymes of the citric acid cycle are present in the mitochondrial matrix. The inner membrane of the mitochondrion is a tight barrier between the matrix and the cytosol, very few compounds can cross the barrier without a specific transport protein. The citric acid cycle typically takes in acetyl-CoA from pyruvate that has been decarboxylated or from fatty acids that have undergone β-oxidation. The carbon is oxidized to CO 2 and reduced electron equivalents (NADH & FADH) and 1 GTP is produced. Conversion of Pyruvate to Acetyl-CoA Pyruvate is transported from the cytosol into the mitochondrion via a specific transporter. There pyruvate dehydrogenase complex releases CO 2 and produces acetyl-CoA. The overall reaction is exergonic and produces NADH. The pyruvate dehydrogenase complex is composed of five enzymes and involves TPP, FAD, lipoic acid and Mg ++ . Enzyme is a flavoprotein. Three of the enzymes are arranged in a compact...
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This note was uploaded on 12/05/2009 for the course BCH 311 taught by Professor Howlett during the Fall '08 term at Rhode Island.

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BCH-5 Citric Acid Cycle - Citric Acid Cycle Citric Acid...

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