In biochemistry,
adenosine triphosphate (ATP) is nucleotide,
known as the "molecularcurrency" of intracellular
energy transfers. ATP is a
means of storing and transporting chemical
energy; both within the cells, and as a precursor for the formation of nucleic
acids. Chemically, ATP consists of adenosine
and three phosphate
groups; energy is released, by hydrolysis
of the third phosphate group. Having released the phosphate group, ATP can absorb
energy and regain the group; this allows ATP to store energy, like a "battery".
Living cells also have other "high-energy" nucleoside
triphosphates, such as guanine triphosphate. Between them and ATP, energy can
be easily transferred with reactions such as those catalyzed by nucleoside diphosphokinase:
Energy is released when hydrolysis
of the phosphate-phosphate
bonds is carried out. This energy can be used by a
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variety of enzymes, motor
proteins, and transport proteins to carry out the work of the cell. Also, the
hydrolysis yields free inorganic phosphate
and adenosine
diphosphate, which can be broken down further to another phosphate ion and
adenosine
monophosphate. ATP can also be broken down to adenosine
monophosphate directly, with the formation of pyrophosphate.
This last reaction has the advantage of being effectively irreversible in aqueoussolution.
