Refer to Figure 9.2, showing the citric acid cycle, as a guide to answer the following questions.

-Inside an active mitochondrion, most electrons follow which pathway?
A)glycolysis → NADH → oxidative phosphorylation → ATP → oxygen
B)citric acid cycle → FADH2 → electron transport chain → ATP
C)electron transport chain → citric acid cycle → ATP → oxygen
D)pyruvate → citric acid cycle → ATP → NADH → oxygen
E)citric acid cycle → NADH → electron transport chain → oxygen

Question

Refer to Figure 9.2, showing the citric acid cycle, as a guide to answer the following questions.
 
-Inside an active mitochondrion, most electrons follow which pathway?
A)glycolysis → NADH → oxidative phosphorylation → ATP → oxygen 
B)citric acid cycle → FADH2 → electron transport chain → ATP 
C)electron transport chain → citric acid cycle → ATP → oxygen 
D)pyruvate → citric acid cycle → ATP → NADH → oxygen 
E)citric acid cycle → NADH → electron transport chain → oxygen

Quizplus · Accepted Answer

Inside an active mitochondrion, most electrons follow the pathway of citric acid cycle → NADH → electron transport chain → oxygen. This is because the citric acid cycle produces NADH, which is a high-energy electron carrier that is used by the electron transport chain to generate ATP through oxidative phosphorylation. Oxygen is the final electron acceptor in the electron transport chain, which allows for the regeneration of NAD+ and FADH2 to continue the cycle. Therefore, choice E is the best answer.