The Electron Transport

The question asks to identify the incorrect statement among the given options related to aerobic respiration and the electron transport chain (ETC). Let's evaluate each option:

1. During aerobic respiration, the role of oxygen is limited to the terminal stage.
   • Oxygen acts as the final electron acceptor in the electron transport chain. It combines with electrons and protons to form water. Therefore, this statement is correct.
2. In ETC, one molecule of gives rise to 2 ATP molecules, and one gives rise to ATP molecules.
   • This statement is incorrect. The actual yield is the reverse: Typically, one molecule of results in approximately 3 ATP molecules, and one molecule of yields about 2 ATP molecules.
3. ATP is synthesized through complex .
   • This statement is correct. The synthesis of ATP occurs via ATP synthase, which is indeed part of complex V in the electron transport chain.
4. Oxidation-reduction reactions produce a proton gradient in respiration.
   • This statement is correct. The transfer of electrons through the ETC is coupled with the translocation of protons across the mitochondrial membrane, creating a proton gradient.

Therefore, the incorrect statement is: "In ETC (Electron Transport Chain), one molecule of gives rise to 2 ATP molecules, and one gives rise to ATP molecules."