What is the final product when oxygen accepts electrons in the electron transport chain?

When oxygen accepts electrons in the electron transport chain, it serves as the final electron acceptor in cellular respiration, specifically during aerobic respiration. As electrons pass through the chain, they move from one protein complex to another, ultimately leading to the reduction of oxygen. This process is crucial because it helps maintain the flow of electrons through the chain, allowing ATP to be produced efficiently.

The reduction of oxygen occurs when it combines with protons (H+ ions) that have also been generated during earlier stages of respiration. This reaction leads to the formation of water, which is the final product of the electron transport chain. Water is essential for cellular metabolism and is expelled by the organism as a waste product.

The presence of other options provides clarity on the metabolic processes that do not occur in this context. For instance, carbon dioxide is produced during the Krebs cycle, glucose is a reactant in glycolysis, and lactic acid is produced under anaerobic conditions when oxygen is not present. Understanding these relationships helps to clarify why water is the correct answer in the context of aerobic respiration and the role of oxygen in the electron transport chain.