The process by which cells convert stored energy into usable forms is called cellular respiration. This metabolic pathway primarily involves the breakdown of glucose in the presence of oxygen, resulting in ATP production. Cellular respiration can be categorized into three main stages: glycolysis, the Krebs cycle, and the electron transport chain. The energy harvested during these stages is crucial for fueling cellular activities, such as muscle contraction, nerve impulse transmission, and biosynthesis.