In aerobic metabolic pathways, the primary chemical reaction that uses oxygen is cellular respiration, specifically during the process of oxidative phosphorylation. This process occurs in the mitochondria of cells and is the final stage of aerobic respiration.
During oxidative phosphorylation, oxygen acts as the final electron acceptor in the electron transport chain. As electrons are transferred through a series of protein complexes, their energy is used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient then drives the synthesis of ATP (adenosine triphosphate), the energy currency of the cell, through a process called chemiosmosis.
The oxygen, after accepting electrons, combines with protons (H+) to form water (H2O). This transformation is crucial as it helps maintain the flow of electrons through the electron transport chain, allowing for continued ATP production. Without oxygen, the electron transport chain would halt, leading to a significant decrease in ATP production and ultimately compromising cellular function.