Adenosine triphosphate
Adenosine triphosphate (ATP) is used as a source of free energy to drive reactions in the cell. Hydrolysis of ATP is slow in the absence of catalysis. Enzymes couple ATP hydrolysis to reactions whose equilibrium lies on the side of the reactants. Enzymes that utilize ATP hydrolysis including motor proteins like myosin, ion pumps, and many biosynthetic enzymes. ATP also is the source of phosphate for many phosphorylation reactions. In eukaryotes, ATP is synthesized mainly in mitochondria (and chloroplasts in plants).
StructureStructure
ATP (reload ) contains a nitrogenous base (adenine ), a sugar (ribose ) and the triphosphate group (). Within enzyme active sites, the beta and gamma phosphate groups often bind to a magnesium cation which helps negatively charged nucleophiles to approach the negatively charged triphosphate group. The most common yields ADP, but in some reactions the product is AMP. |
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