What role does oxygen play in cellular respiration?

Oxygen plays a crucial role in cellular respiration by acting as the final electron acceptor in the electron transport chain, which is the last stage of cellular respiration. During this process, electrons that are harvested from glucose are transferred through a series of proteins embedded in the inner mitochondrial membrane. This transfer of electrons creates a proton gradient that powers ATP synthesis.

When the electrons reach the end of the electron transport chain, they need a final acceptor to prevent a backup and allow the entire process to continue. Oxygen fulfills this role by combining with these electrons and protons to form water. This is vital, as the presence of oxygen ensures the continuous flow of electrons, maximizing ATP production. Without oxygen, the electron transport chain cannot function effectively, leading to a significant decrease in ATP yield as cells revert to less efficient anaerobic pathways to produce energy.

In contrast, the other choices do not accurately describe oxygen's role in cellular respiration. Oxygen is not the primary source of energy for ATP production; instead, it enables the extraction of energy during the later stages. It is also not converted to glucose in photosynthesis—photosynthesis is a separate process that uses carbon dioxide and water to create glucose in plant cells. Additionally, oxygen does not inhibit glycolysis;