Which of the following statements is incorrect

Options

A. In ETC (Electron Transport Chain), one molecule of NADH + `H^+` gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules
B. ATP is synthesized through complex V
C. Oxidation-reduction reactions produce proton gradient in respiration
D. During aerobic respiration, role of oxygen is limited to the terminal stage

Explanation

To determine which statement is incorrect regarding the electron transport chain and ATP synthesis, we can analyze the provided statements step by step:

### Step-by-Step Solution:

1. **Analyze the First Statement**:
- The statement claims that one molecule of NADH + H+ gives rise to two ATP molecules and one FADH2 gives rise to three ATP molecules.
- This is incorrect because, in the electron transport chain (ETC), one molecule of NADH typically generates three ATP molecules, while one molecule of FADH2 generates only two ATP molecules.

2. **Analyze the Second Statement**:
- The statement says that ATP is synthesized through complex V.
- This statement is correct. Complex V, also known as ATP synthase, is responsible for synthesizing ATP by utilizing the proton gradient created by the previous complexes.

3. **Analyze the Third Statement**:
- The statement mentions that oxidation-reduction reactions produce a proton gradient during respiration.
- This statement is also correct. The oxidation-reduction reactions in the electron transport chain lead to the pumping of protons (H+) into the intermembrane space, creating a proton gradient.

4. **Analyze the Fourth Statement**:
- The statement indicates that during aerobic respiration, the role of oxygen is limited to the terminal stage.
- This statement is correct as well. Oxygen acts as the final electron acceptor in the electron transport chain, forming water at the end of the process.

5. **Conclusion**:
- After analyzing all the statements, it is clear that the first statement is incorrect. Therefore, the answer to the question is that the first statement is the incorrect one.

### Final Answer:
The incorrect statement is: "One molecule of NADH + H+ gives rise to two ATP molecules and one FADH2 gives rise to three ATP molecules."

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