Assuming glucose is the only energy source for a cell,what fraction of the carbon dioxide produced by aerobic respiration is generated by the reactions of the citric acid cycle?
A)1/6
B)1/3
C)1/2
D)2/3
E)all of it

Question

Quizplus · Accepted Answer

During aerobic respiration, glucose is oxidized to pyruvate through glycolysis, which occurs in the cytoplasm. Pyruvate then enters the mitochondria where it is converted into Acetyl-CoA, which enters the citric acid cycle. In the citric acid cycle, Acetyl-CoA is oxidized and gives off CO2 as a byproduct. Therefore, two molecules of CO2 are produced per molecule of Acetyl-CoA. Since each glucose molecule produces 2 molecules of Acetyl-CoA, there will be a total of 4 CO2 molecules generated during the citric acid cycle. However, during the preceding steps of glycolysis and the transition reaction, glucose is converted into pyruvate and then Acetyl-CoA, which also produces a total of 2 CO2 molecules. Therefore, out of the total of 6 CO2 molecules produced by the complete oxidation of glucose, 4 are produced in the citric acid cycle. This gives a fraction of 4/6, which simplifies to 2/3.

Assuming Glucose Is the Only Energy Source for a Cell,what