The process by which cells use oxygen to break down glucose is known as cellular respiration. During this process, glucose is converted into ATP, the energy currency of the cell, along with the byproducts of carbon dioxide and water. This occurs mainly in the mitochondria of eukaryotic cells, following a series of reactions that involve glycolysis, the Krebs cycle, and the electron transport chain. Oxygen plays a crucial role as the final electron acceptor, allowing for maximum energy extraction from glucose.