Question

Which of the following statements is incorrect?

• A. During aerobic respiration, role of oxygen is limited to the terminal stage.
• B. In ETC (Electron Transport Chain), one molecule of $NADH + H^{+}$gives rise to 2 ATP molecules, and one $FADH _{2}$ gives rise to $3$ ATP molecules.
• C. ATP is synthesized through complex $V$.
• D. Oxidation-reduction reactions produce proton gradient in respiration.

Answer 1

The Correct Option is B

To determine which of the given statements is incorrect, we need to evaluate each option based on our understanding of aerobic respiration and the electron transport chain (ETC).

1. During aerobic respiration, role of oxygen is limited to the terminal stage.

   Oxygen acts as the final electron acceptor at the end of the electron transport chain, combining with electrons and protons to form water. Its role is indeed limited to this final stage. Therefore, this statement is correct.

2. In ETC (Electron Transport Chain), one molecule of $NADH + H^{+}$ gives rise to 2 ATP molecules, and one $FADH_{2}$ gives rise to $3$ ATP molecules.

   This is incorrect. Generally, one NADH typically generates approximately 3 ATP, while one FADH₂ results in about 2 ATP. Therefore, the statement provided is opposite to the usually accepted figures. This is the incorrect statement.

3. ATP is synthesized through complex $V$.

   ATP synthesis occurs mainly in the ATP synthase enzyme, which is referred to as Complex V in the electron transport chain. This statement is correct.

4. Oxidation-reduction reactions produce proton gradient in respiration.

   Oxidation-reduction reactions within the electron transport chain create a proton gradient across the inner mitochondrial membrane, essential for ATP synthesis. Hence, this statement is correct.

The incorrect statement from the options is: "In ETC (Electron Transport Chain), one molecule of $NADH + H^{+}$ gives rise to 2 ATP molecules, and one $FADH_{2}$ gives rise to $3$ ATP molecules."