Aerobic respiration is a process cells use to generate energy with the help of oxygen. It starts with glucose being broken down into pyruvate in the cytoplasm, producing a small amount of ATP. The pyruvate then enters the mitochondria, where it's converted to acetyl-CoA and enters the citric acid cycle. This cycle produces more energy carriers and releases carbon dioxide.

In the final stage, the electron transport chain in the mitochondria uses these energy carriers to create a proton gradient, which drives the production of a large amount of ATP. Oxygen is essential here, as it combines with electrons and protons to form water. This entire process efficiently produces ATP, the energy currency of the cell.