Editing ATP hydrolysis (section)

{{Short description|Catabolism of ATP into ADP}}

[[Image:Adenosintriphosphat protoniert.svg|200px|thumb|Structure of ATP]]
[[Image:Adenosindiphosphat protoniert.svg|200px|thumb|Structure of ADP]]
[[Image:Ortho resonance.svg|350px|thumb|Four possible resonance structures for inorganic phosphate]]

'''ATP hydrolysis''' is the catabolic reaction process by which [[chemical energy]] that has been stored in the [[High energy phosphate|high-energy phosphoanhydride bonds]] in [[adenosine triphosphate]] (ATP) is released after splitting these bonds, for example in [[muscle]]s, by producing work in the form of [[mechanical energy]]. The product is [[adenosine diphosphate]] (ADP) and an [[inorganic phosphate]] (P<sub>i</sub>). ADP can be further hydrolyzed to give energy, [[adenosine monophosphate]] (AMP), and another inorganic phosphate (P<sub>i</sub>).<ref name=":0">{{Cite book|title=Molecular cell biology|last=Lodish, Harvey|date=2013|publisher=W.H. Freeman and Co|isbn=9781464109812|edition=7th|location=New York|pages=52, 53|oclc=171110915}}</ref> ATP hydrolysis is the final link between the energy derived from food or sunlight and useful work such as [[muscle contraction]], the establishment of [[electrochemical gradient]]s across membranes, and biosynthetic processes necessary to maintain life.

Anhydridic bonds are often labelled as "''high-energy bonds"''. P-O bonds are in fact fairly strong (~30 kJ/mol stronger than C-N bonds)<ref name="Darwent1970"> Darwent, B. deB. (1970). "Bond Dissociation Energies in Simple Molecules", Nat. Stand. Ref. Data Ser., Nat. Bur. Stand. (U.S.) 31, 52 pages.</ref><ref name="WiredChemist bond energies"> {{Cite web|url=http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html|title=Common Bond Energies (D|website=www.wiredchemist.com|access-date=2020-04-04}} </ref> and themselves not particularly easy to break. As noted below, energy is released by the hydrolysis of ATP. However, when the P-O bonds are broken, ''input'' of energy is required. It is the formation of new bonds and lower-energy inorganic phosphate with a ''release of a larger amount of energy'' that lowers the total energy of the system and makes it more stable.<ref name=":0" />

[[Hydrolysis]] of the [[phosphate]] groups in ATP is especially [[exergonic]], because the resulting inorganic phosphate molecular ion is greatly stabilized by multiple [[resonance structures]], making the products (ADP and P<sub>i</sub>) lower in energy than the reactant (ATP). The high negative charge density associated with the three adjacent phosphate units of ATP also destabilizes the molecule, making it higher in energy. Hydrolysis relieves some of these electrostatic repulsions, liberating useful energy in the process by causing conformational changes in enzyme structure.

In humans, approximately 60 percent of the energy released from the hydrolysis of ATP produces metabolic heat rather than fuel the actual reactions taking place.<ref>{{Cite book|title=Berne & Levy physiology|date=2010|publisher=Mosby/Elsevier|others=Berne, Robert M., 1918-2001., Koeppen, Bruce M., Stanton, Bruce A.|isbn=9780323073622|edition=6th, updated|location=Philadelphia, PA|oclc=435728438}}</ref>
Due to the acid-base properties of ATP, ADP, and inorganic phosphate, the hydrolysis of ATP has the effect of lowering the pH of the reaction medium. Under certain conditions, high levels of ATP hydrolysis can contribute to [[lactic acidosis]].