AEROBIC CELLULAR RESPIRATION - the acetyl group combines...

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AEROBIC CELLULAR RESPIRATION In aerobic cells, the next major step will be a series of reactions known as the Kreb’s Cycle  (tricarboxylic acid or citric acid cycle).  Before this begins, a preparatory step will change the pyruvic acid left over from glycolysis to  acetyl coenzyme A. One molecule of carbon dioxide is released and the remaining part of the  pyruvic acid molecule, an acetyl group, combines with coenzyme A. Also, another NAD+ is  reduced to NADH in this step. Since 2 pyruvic acids were produced from one glucose, 2 acetyl  CoAs will be produced and 2 NAD+s will be reduced to 2 NADHs in this step for each glucose  molecule. As each acetyl CoA enters the Kreb’s Cycle, the molecule separates. Coenzyme A detaches and 
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Unformatted text preview: the acetyl group combines with oxaloacetic acid to form citric acid. SEE F IGURE 5.13 P. 126 FOR THE REACTIONS THAT MAKE UP THE KREB’S CYCLE As the Kreb’s cycle proceeds, the following are produced for every 2 acetyl CoAs: 4 CO 2 6 NADH 2 FADH 2 2 ATPs (substrate-level phosphorylation) The reduced coenzyme molecules are very important, because they will be used as electron donors in the electron transport chain to produce large amounts of ATP. At the same time, by donating the hydrogen they had gained, they will be returned to the functional coenzyme form, NAD+, and be available to catalyze another reaction....
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