Respiration

Respiration is the physiological process by which organisms supply oxygen to their cells and the cells use that oxygen to produce high energy molecules. Respiration occurs in all types of organisms, including bacteria, protists, fungi, plants, and animals. In higher animals, respiration is often separated into three separate components: (a) external respiration, the exchange of oxygen and carbon dioxide between the environment and the organism; (b) internal respiration, the exchange of oxygen and carbon dioxide between the internal body fluids, such as blood, and individual cells; and (c) cellular respiration, the biochemical oxidation of glucose and consequent synthesis of ATP (adenosine triphosphate).