What is the primary function of the electron transport chain in cellular respiration?

• A. To break down fatty acids into acetyl-CoA
• B. To directly synthesize glucose from pyruvate
• C. To convert ATP into ADP and inorganic phosphate
• D. To generate a proton gradient across the inner mitochondrial membrane

Answer: (D)

Verified step by step guidance

1. Understand the context: The electron transport chain (ETC) is the final stage of cellular respiration, occurring in the inner mitochondrial membrane. Its primary role is to facilitate energy production in the cell.
2. Recognize the key components: The ETC consists of protein complexes (I, II, III, IV) and mobile electron carriers. Electrons are transferred through these complexes, originating from NADH and FADH₂ produced in earlier stages of cellular respiration.
3. Explain the mechanism: As electrons move through the ETC, energy is released. This energy is used to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating a proton gradient across the inner mitochondrial membrane.
4. Clarify the purpose of the proton gradient: The proton gradient establishes a difference in proton concentration and electrical charge across the membrane. This gradient is a form of potential energy, which drives the synthesis of ATP via ATP synthase in the final step of cellular respiration.
5. Summarize the primary function: The main role of the electron transport chain is to generate the proton gradient across the inner mitochondrial membrane, which is essential for ATP production during oxidative phosphorylation.