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

• A. ATP is synthesized through oxidative phosphorylation.
• B. NADH is converted into NAD+ in the cytoplasm.
• C. Glucose is broken down into pyruvate.
• D. Carbon dioxide is fixed into organic molecules.

Answer: (A)

Verified step by step guidance

1. Understand that the electron transport chain (ETC) is a series of protein complexes located in the inner mitochondrial membrane, crucial for cellular respiration.
2. Recognize that the primary function of the ETC is to facilitate the transfer of electrons from electron donors like NADH and FADH2 to oxygen, the final electron acceptor.
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. Learn that this proton gradient generates a chemiosmotic potential, which drives the synthesis of ATP from ADP and inorganic phosphate (Pi) through a process called oxidative phosphorylation, catalyzed by ATP synthase.
5. Note that the other options provided (conversion of NADH to NAD+ in the cytoplasm, breakdown of glucose into pyruvate, and carbon dioxide fixation) occur in different cellular processes, not in the electron transport chain.