ATP hydrolysis
1524792
199475753
2008-03-20T00:11:52Z
Epbr123
1395162
Reverted edits by [[Special:Contributions/75.128.61.28|75.128.61.28]] to last version by XLinkBot
'''ATP hydrolysis''' is the reaction by which chemical energy that has been stored and transported in the [[High energy phosphate|high-energy phosphoanhydridic bonds]] in [[adenosine triphosphate|ATP]] (Adenosine triphosphate) is released, for example in the muscles, to produce work. The product is [[adenosine diphosphate|ADP]] (Adenosine diphosphate) and an [[inorganic phosphate]], orthophosphate (Pi). ADP can be further hydrolyzed to give energy, [[adenosine monophosphate|AMP]] (Adenosine monophosphate), and another orthophosphate (Pi). ATP hydrolysis is the final link between the energy derived from food or sunlight and useful work such as muscle contraction, the establishment of ion gradients across membranes, and biosynthetic processes necessary to maintain life.
[[Hydrolysis]] of the [[phosphate]] groups in ATP is especially [[exergonic]], because the resulting orthophosphate group is greatly stabilized by multiple [[resonance structures]], making the products (ADP and P<sub>i</sub>) much 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 as well, liberating useful energy in the process.
Hydrolysis of the terminal phosphoanhydridic bond is a highly exergonic process, producing -30.5 kJ mol<sup>-1</sup> energy. This reaction can then be coupled with thermodynamically unfavorable reactions to give an overall negative (spontaneous) '''Δ'''G for the reaction sequence. The actual value of '''Δ'''G for ATP hydrolysis varies, primarily depending on Mg<sup>2+</sup> concentration, and under normal physiologic conditions is actually closer to -50 kJ mol<sup>-1</sup>.
In humans, approximately 60% of the energy released from the hydrolysis of one [[Mole (unit)|mole]] of ATP produces metabolic heat rather than fuel the actual reactions taking place.{{Fact|date=January 2008}}
[[Image:ATP structure.svg|200px|thumb|Structure of ATP]]
[[Image:ADP structure.svg|200px|thumb|Structure of ADP]]
[[Image:Ortho_resonance.JPG|350px|thumb|Four possible resonance structures for orthophosphate]]
==See also==
*[[Dephosphorylation]]
[[Category:Cellular respiration]]
[[Category:Exercise physiology]]
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