The process that converts energy from food into cellular energy is termed cellular respiration. This metabolic process involves a series of biochemical reactions where glucose and oxygen are transformed into ATP (adenosine triphosphate), the energy currency of cells. Cellular respiration comprises three main stages: glycolysis, the citric acid cycle, and the electron transport chain. It provides vital energy for cellular functions, growth, and repair, making it essential for all living organisms. The efficiency of this process can vary based on the availability of oxygen and other factors.