Which of the following events takes place in the electron transport chain?

• A. The breakdown of glucose into six carbon dioxide molecules.
• B. The breakdown of NADH and FADH2 to carbon dioxide.
• C. Harnessing energy from high-energy electrons derived from glycolysis, pyruvate oxidation, and the Krebs cycle.
• D. Substrate-level phosphorylation.

Answer: (C)

Verified step by step guidance

1. Understand that the electron transport chain (ETC) is the final stage of cellular respiration, occurring in the inner mitochondrial membrane.
2. Recognize that the primary function of the ETC is to transfer electrons from NADH and FADH2 to oxygen, which is the final electron acceptor, forming water.
3. Identify that as electrons move through the ETC, energy is released and used to pump protons (H+) across the mitochondrial membrane, creating a proton gradient.
4. Realize that this proton gradient is used by ATP synthase to produce ATP from ADP and inorganic phosphate, a process known as oxidative phosphorylation.
5. Note that the breakdown of glucose into carbon dioxide occurs earlier in cellular respiration, specifically during glycolysis and the Krebs cycle, not in the ETC.