Apentix/AP Biology/Unit 3: Cellular Energetics/Question

AP Biologymediummcq1 pt

For each acetyl-CoA oxidized by one turn of the Krebs cycle, the products include...

A.one CO2, two NADH, one FADH2, and two ATP equivalents

B.three CO2, four NADH, and one FADH2

C.two CO2, three NADH, one FADH2, and one ATP equivalent

D.two pyruvate molecules recycled back toward glycolysis

Explanation

Core Concept

Per acetyl-CoA, one turn of the citric acid cycle produces two CO2, three NADH, one FADH2, and one GTP/ATP equivalent. That stoichiometry is correct. However, the first turn's two decarboxylations generally remove carbons derived from the pre-existing oxaloacetate rather than the two acetyl carbons that just entered. Those acetyl-derived carbons are randomized through the cycle and are typically released in later turns.

Correct Answer

Ctwo CO2, three NADH, one FADH2, and one ATP equivalent

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