Which of the following best describes the electron transport chain?

• A. Electrons are pumped across a membrane by active transport.
• B. Acetyl CoA is fully oxidized to CO₂.
• C. Hydrogen atoms are added to CO₂ to make an energy-rich compound.
• D. Glucose is broken down to a three-carbon compound in preparation for the citric acid cycle.
• E. Electrons are passed from one carrier to another, releasing a little energy at each step.

Answer: (E)

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.
2. Recognize that the primary function of the ETC is to transfer electrons from electron donors like NADH and FADH2 to electron acceptors such as oxygen, through a series of redox reactions.
3. Note that as electrons move through the chain, they release energy, which is used to pump protons (H+) across the mitochondrial membrane, creating a proton gradient.
4. This proton gradient generates a potential energy difference across the membrane, which is used by ATP synthase to produce ATP from ADP and inorganic phosphate.
5. The correct description of the electron transport chain is that electrons are passed from one carrier to another, releasing a little energy at each step, which is used to create a proton gradient for ATP synthesis.