TAILIEUCHUNG - Biochemistry, 4th Edition P61

Biochemistry, 4th Edition P61. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | 19 The Tricarboxylic Acid Cycle ESSENTIAL QUESTION The glycolytic pathway converts glucose to pyruvate and produces two molecules of ATP per glucose only a small fraction of the potential energy available from glucose. Under anaerobic conditions pyruvate is reduced to lactate in animals and to ethanol in yeast and much of the potential energy of the glucose molecule remains untapped. In the presence of oxygen however a much more interesting and thermodynamically complete story unfolds. How is pyruvate oxidized under aerobic conditions and what is the chemical logic that dictates how this process occurs Under aerobic conditions pyruvate from glycolysis is converted to acetyl-coenzyme A acetyl-CoA and oxidized to CO2 in the tricarboxylic acid TCA cycle also called the citric acid cycle . The electrons liberated by this oxidative process are passed via NADH and FADH2 through an elaborate membrane-associated electrontransport pathway to O2 the final electron acceptor. Electron transfer is coupled to creation of a proton gradient across the membrane. Such a gradient represents an energized state and the energy stored in this gradient is used to drive the synthesis of many equivalents of ATP. ATP synthesis as a consequence of electron transport is termed oxidative phosphorylation the complete process is diagrammed in Figure . Aerobic pathways permit the production of 30 to 38 molecules of ATP per glucose oxidized. Although two molecules of ATP come from glycolysis and two more directly out of the TCA cycle most of the ATP arises from oxidative phosphorylation. Specifically reducing equivalents released in the oxidative reactions of glycolysis pyruvate decarboxylation and the TCA cycle are captured in the form of NADH and enzymebound FADH2 and these reduced coenzymes fuel the electron-transport pathway and oxidative phosphorylation. Complete oxidation of glucose to CO2 involves the removal of 24 electrons that is it is a 24-electron oxidation. In glycolysis 4 .

• Sinh học
• Nền tảng của hóa sinh học
• trao đổi chất protein
• RNA trao đổi chất
• nguyên tắc của hóa sinh
• Axit amin
• công nghệ DNA