The process by which living organisms convert food into energy is called cellular respiration. During cellular respiration, glucose and oxygen are transformed into water, carbon dioxide, and ATP (adenosine triphosphate), which is the energy currency of the cell. This process takes place in the mitochondria of eukaryotic cells and involves several stages, including glycolysis, the Krebs cycle, and the electron transport chain. In anaerobic conditions, organisms may also undergo fermentation as an alternative energy conversion pathway. Overall, cellular respiration is essential for life's energy needs, allowing cells to carry out various functions necessary for survival.