respiration The metabolic process in which complex organic substances are broken down into simpler products with the release of energy. This energy is incorporated into the energy-carrying substance ATP and subsequently used for other metabolic processes. Respiration is carried out within the cells of organisms by the citric acid cycle (Kreb's cycle) and oxidative phosphorylation. Related category • ANATOMY AND PHYSIOLOGY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |