The synthesis of ATP from ADP and phosphate and its role as the immediate source of energy for biological processes.

Synthesis

ATP and ADP + an inorganic phosphate

ATP is made up of adenine, ribose and three phosphates. When energy needs to be released, the last phosphate group is broken off by hydrolysis (bonding the molecule with water), releasing energy stored in the bond. This leaves ADP and an inorganic phosphate, which can be turned back into ATP by condensation (removal of water).

ATP + H2O > ADP +P(i)
ADP + P(i) > ATP + H2O

Energy source

Energy is released in suitable, small amounts.
It is soluble.
There is a single, simple reaction to release it.

Energy is needed for the processes that living things carry out, for example active transport, muscle contraction, glycolysis.