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The TCA Cycle

  • The tricarboxylic acid cycle (TCA cycle) is not merely an extension of glycolysis. It is the central metabolic pathway in cellular respiration. Intermediates are fed into the cycle from the catabolism of carbohydrates, fats, and proteins.

  • In the TCA cycle, a series of eight reactions oxidize acetyl residues to carbon dioxide. These oxidation reactions release energy that’s captured and used to synthesize ATP. This is the big pay-off in aerobic metabolism. Enough energy is released to synthesize 10–12 molecules of ATP!

  • In this Lesson, we’ll study the reactions of the TCA cycle in detail. We’ll also see how this pathway is regulated and transfers energy.