How many CO2 molecules are produced in one turn of the Citric Acid Cycle?

In one turn of the Citric Acid Cycle, a total of two carbon dioxide (CO2) molecules are produced. Each turn of the cycle processes a single acetyl-CoA, which is a two-carbon molecule. This acetyl group is completely oxidized during the cycle, ultimately leading to the release of carbon dioxide.

The cycle begins with the condensation of acetyl-CoA with oxaloacetate to form citrate, a six-carbon intermediate. As the cycle progresses through a series of enzymatic reactions, two carbon atoms are gradually removed in the form of CO2. Specifically, these are generated during the decarboxylation steps, where the cycle transitions through various forms, including isocitrate and alpha-ketoglutarate, ultimately regenerating oxaloacetate to continue the cycle.

Thus, each complete turn of the Citric Acid Cycle results in the release of two CO2 molecules, reflecting the complete oxidation of the original acetyl group. This plays a vital role in cellular respiration, linking the oxidation of substrates with the production of CO2 as a waste product and the generation of energy in the form of NADH and FADH2.