The cellular process that converts food into ATP is known as cellular respiration. This process occurs in the mitochondria of cells and involves three main stages: glycolysis, the Krebs cycle, and oxidative phosphorylation. During cellular respiration, glucose is broken down, and energy is extracted in the form of ATP, which serves as the energy currency in cells. Oxygen may be required for aerobic respiration, while anaerobic respiration occurs without it.