What fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle, if glucose is the sole energy source?
A) 1/6
B) 1/3
C) 1/2
D) 2/3
E) 100/100

Question

Quizplus · Accepted Answer

When glucose is the sole energy source, the citric acid cycle (also known as the Krebs cycle or TCA cycle) is responsible for generating two-thirds of the carbon dioxide exhaled by animals. This is because for each molecule of glucose metabolized, two molecules of CO2 are released during the conversion of pyruvate to acetyl-CoA (before the citric acid cycle), and four molecules of CO2 are released during the citric acid cycle itself. Since glucose metabolism results in a total of six molecules of CO2, and the citric acid cycle contributes four out of these six, the fraction of CO2 generated by the citric acid cycle is 4/6, which simplifies to 2/3.

What Fraction of the Carbon Dioxide Exhaled by Animals Is