What role does oxygen play in cellular metabolism?

Oxygen plays a crucial role in cellular metabolism primarily by enabling the process of aerobic respiration, which is the method cells use to convert glucose and other nutrients into energy. Specifically, oxygen is essential for the production of adenosine triphosphate (ATP), the energy currency of the cell. During aerobic respiration, oxygen acts as the final electron acceptor in the electron transport chain, which occurs within the mitochondria. This process efficiently generates ATP—significantly more than anaerobic processes.

In the presence of oxygen, cells can oxidize glucose completely, resulting in the production of carbon dioxide and water as byproducts, while generating a higher yield of ATP. This is why oxygen is considered vital for aerobic metabolism and why it is often associated with high-energy demands of cells, particularly those in tissues that are actively engaged in metabolic activities, like muscle cells during exercise.

Other options do not accurately reflect the fundamental physiological role of oxygen. While digestion involves many processes, oxygen's primary function is not directly related to digesting food. Anaerobic metabolism, by definition, occurs without oxygen and does not involve ATP production through aerobic processes. Finally, oxygen is not produced as a waste product; rather, it is consumed in cellular respiration. Thus,