How does oxygen act as a final electron acceptor?

Oxygen acts as the final electron acceptor in the electron transport chain during oxidative phosphorylation. At the end of the chain, electrons that have passed through multiple protein complexes are transferred to oxygen molecules.

Oxygen has a high affinity for electrons, making it an effective acceptor. It combines with these electrons and protons (H⁺ ions) from the mitochondrial matrix to form water. The reaction can be summarized as:

O₂ + 4e⁻ + 4H⁺ → 2H₂O

This step is essential because it removes electrons from the electron transport chain, allowing the continuous flow of electrons through the system. Without oxygen, electrons would accumulate, and the entire chain would come to a halt.

If the electron transport chain stops, the proton gradient cannot be maintained, and ATP synthesis through ATP synthase ceases. This is why oxygen is critical for aerobic respiration and efficient energy production.

Overall, oxygen ensures the smooth functioning of cellular respiration by acting as the terminal electron acceptor and enabling continuous ATP generation.