Question

The end products of the citric acid cycle include all of the following except

A) CO₂.
B) pyruvate.
C) ATP.
D) NADH.
E) FADH₂.

Answer 1

The end product of the citric acid cycle that is not included is pyruvate. Pyruvate is used to form acetyl CoA before entering the citric acid cycle, while the cycle produces CO₂, ATP, NADH, and FADH₂.

Step-by-step explanation:

The end products of the citric acid cycle include CO₂, ATP, NADH, and FADH₂, but not pyruvate. Pyruvate is actually consumed before the citric acid cycle begins; it is converted into acetyl CoA during a process called pyruvate oxidation. Therefore, the correct answer to the question is B) pyruvate. In the citric acid cycle, acetyl CoA is combined with a four-carbon oxaloacetate to form citrate.

The citrate is then oxidized, releasing CO₂ and reducing NAD+ to NADH and FAD to FADH₂, while also producing ATP (or GTP, depending on the cell type) through substrate-level phosphorylation.

Answer 2

The citric acid cycle does not produce pyruvate; instead, pyruvate is consumed after being converted to acetyl CoA. The cycle produces CO₂, NADH, FADH₂, and ATP or GTP.

Step-by-step explanation:

The end products of the citric acid cycle include CO₂ (carbon dioxide), NADH (Nicotinamide Adenine Dinucleotide in its reduced form), FADH₂ (Flavin Adenine Dinucleotide in its reduced form), and ATP (Adenosine Triphosphate) or GTP (Guanosine Triphosphate). Among these options, pyruvate is not an end product of the citric acid cycle; it is actually one of the reactants that enters the Krebs cycle after being converted to acetyl CoA. Therefore, the correct answer is B) pyruvate.