The primary role of oxygen in cellular respiration is to act as the final electron acceptor in the electron transport chain, a crucial stage in the production of ATP. Cellular respiration involves the breakdown of glucose to release energy, which is used to produce ATP, the energy currency of cells. Oxygen is necessary for aerobic respiration, allowing organisms to extract maximum energy from nutrients. Without oxygen, cells must rely on anaerobic processes, which are less efficient and may lead to the accumulation of metabolic waste products.