Organic compound, substrate in many enzyme-catalyzed reactions (see catalysis) in the cells of animals, plants, and microorganisms. ATP's chemical bonds (see bonding) store a large amount of chemical energy. ATP therefore functions as the carrier of chemical energy from energy-yielding oxidation (see oxidation-reduction) of food to energy-demanding cellular processes. Three such processes of metabolism are sources of ATP and stored energy: fermentation, the tricarboxylic acid cycle, and cellular respiration (also called oxidative phosphorylation). All form ATP from adenosine monophosphate (AMP) or adenosine diphosphate (ADP) and inorganic phosphate. When the reaction goes in the other direction, ATP is broken down to ADP or AMP and phosphate, and the released energy is used to perform chemical, electrical, or osmotic work for the cell.

Variants of ATP

ATP in full adenosine triphosphate

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