In the electron transport chain, electrons flow from NADH and FADH2 to

In the electron transport chain, electrons flow from NADH and FADH2 to

• A. Electrons flow from NADH/FADH2 to oxygen
• B. Electrons flow from oxygen to NADH
• C. Electrons flow from CO2 to glucose
• D. Electrons do not move; they stay stationary

Answer: (A)

Electrons flow through the electron transport chain from NADH and FADH2 to the final electron acceptor, oxygen, which accepts them and, with protons, forms water. As these electrons move through the protein complexes, their energy pumps protons across the inner mitochondrial membrane, creating a proton gradient that powers ATP synthase to make ATP. This setup relies on oxygen being the last recipient of electrons; without it, the chain backs up and ATP production halts. The other ideas don’t fit: electrons aren’t moving from oxygen back to NADH, carbon dioxide to glucose isn’t part of the electron transport chain, and electrons do move rather than staying stationary.

Electrons flow through the electron transport chain from NADH and FADH2 to the final electron acceptor, oxygen, which accepts them and, with protons, forms water. As these electrons move through the protein complexes, their energy pumps protons across the inner mitochondrial membrane, creating a proton gradient that powers ATP synthase to make ATP. This setup relies on oxygen being the last recipient of electrons; without it, the chain backs up and ATP production halts. The other ideas don’t fit: electrons aren’t moving from oxygen back to NADH, carbon dioxide to glucose isn’t part of the electron transport chain, and electrons do move rather than staying stationary.