In biothermodynamics, ATP or adenosine triphosphate (C10H16N5O13P3) is a five element molecule, classified as a nucleotide, which acts as an energy carrier in biology, often called molecular energy currency, the thermodynamics of which were described by German-born American Fritz Lipmann in 1941. [1] The energy is stored in the three high-energy phosphate bonds is on the magnitude of 20 kJ of free energy per bond per mol, amounting to about 55 kJ per mole of ATP. To release this energy, each phosphate group bond (P–O) can be cleaved, one-by-one, as exergonic reactions, providing enough energy to drive typical endergonic reactions in the cell. An average person at rest hydrolyzes and produces some 40 kg of ATP per day. [2]

References
1. Lipmann, Fritz. (1941). “Metabolic Generation and Utilization of Phosphate Bond Energy”. New York. In: Advances in Enzymology and Related Subjects – Vol. 1 (1941), (pg. 99-162). Interscience Publishers.
2. Purves, William K, Sadava, David, and Orians, Gordon H. (2004). Life: the Science of Biology (section: ATP couples exergonic and endergonic reactions, pgs. 112-13). MacMillian.

External links
● Adenosine triphosphate – Wikipedia.