Adenosine triphosphate (ATP) is the nucleotide known in biochemistry as the "molecular currency" of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. ATP also plays an important role in the synthesis of nucleic acids.
Chemically, ATP consists of adenosine and three phosphate groups. Energy is released by hydrolysis of the third phosphate group. After this third phosphate group is released, the resulting ADP (adenosine diphosphate) can absorb energy and regain the group, thus regenerating an ATP molecule; this allows ATP to store energy like a rechargeable battery.
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2 Other triphosphates
3 See also
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ATP can be produced by various cellular processes, most typically in mitochondria by oxidative phosphorylation under the catalytic influence of ATP synthase or in the case of plants in chloroplasts by photosynthesis.
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 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 aqueous solution.