ATP synthesis is the process by which cells produce adenosine triphosphate (ATP), the primary energy carrier in living organisms. This process mainly occurs in the mitochondria during cellular respiration, where glucose and oxygen are used to generate ATP. The key steps in ATP synthesis involve glycolysis, the Krebs cycle, and the electron transport chain. In these stages, energy from nutrients is converted into ATP through a series of chemical reactions, ultimately allowing cells to perform essential functions like growth, repair, and movement.