05_aerobic respiration

05_aerobic respiration - Aerobic Respiration - 1 - AEROBIC...

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Aerobic Respiration - 1 - AEROBIC RESPIRATION CONCEPTS CHECK LIST [ NOTE. .. This section of BIOL 190A is presented in classes in a manner such that the assigned text readings can be considered as reference material. .. you should consult your text as needed, but rely most heavily on the class presentation and the course pack materials provided by your instructor. Many of the details presented in your text are not required for this course. ] INTRODUCTION Aerobic respiration provides most of the ATP required by aerobic (oxygen-dependent) cells for performing cellular work. Aerobic respiration involves the enzyme-catalyzed reactions of glycolysis, the Krebs cycle, and the mitochondrial electron transport chain. During aerobic respiration, food molecules (esp. glucose, but many others as well) are oxidized to carbon dioxide and water. Two fundamentally different processes are used to make ATP during aerobic respiration: substrate-level phosphorylation and oxidative phosphorylation. In substrate-level phosphorylation, ATP is made from ADP by combining it with a phosphate group that was donated by an organic molecule. In oxidative phosphorylation, ATP is made from ADP by combining it with an inorganic phosphate ion in a process that involves the chemiosmotic flow of protons across a membrane. Oxygen is the final electron acceptor during aerobic respiration. GLYCOLYSIS Glycolysis is a series of enzyme-catalyzed reactions that oxidize glucose to pyruvate, and serves as the starting point for aerobic respiration, fermentation, and many other metabolic pathways. Many of the intermediate molecules created during glycolysis are used in the synthesis of other organic molecules required by the cell, and many molecules can contribute their carbon skeletons to the process (and thus can be used as food molecules in a manner similar to that of glucose). During glycolysis, most of the energy in glucose remains in the molecules of pyruvate it creates, and some is used to create a small amount of ATP and NADH. The reactions of glycolysis occur in virtually all cells (both prokaryotic and eukaryotic). The reactions of glycolysis do not require the presence of oxygen (they are oxygen-independent). All of the reactions of glycolysis occur in the cytosol of the cell. THE PYRUVATE DEHYDROGENASE COMPLEX The pyruvate dehydrogenase complex performs several reactions that ultimately provide a source of carbon for the Krebs cycle (donated two carbons at at a time as an acetyl group donated by acetyl-CoA). The pyruvate dehydrogenase complex occurs in the mitochondrial matrix. This enzyme complex serves as a “bridge” between glycolysis and the Krebs cycle. During the reactions catalyzed by the pyruvate dehydrogenase complex, the 3-carbon pyruvate molecule loses one carbon as carbon dioxide while its other two carbons are donated to reduced coenzyme A (CoASH) to form acetyl-CoA; a molecule of NADH is also created.
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Aerobic Respiration - 2 - THE KREBS CYCLE
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05_aerobic respiration - Aerobic Respiration - 1 - AEROBIC...

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