ATP. Computer graphic representation of a molecule of adenosine triphosphate (ATP). The molecule acts as an intracellular battery of metabolic energy. Energy is stored in the chemical bonds of ATP's three phosphate groups (orange, at left), ready to be released when the molecule is split into its di- or monophosphate relatives (ADP or AMP). Here, wire-drawn forms represent the atomic backbone. At lower centre (white) is a carbon ring; nitrogen atoms (blue) occur in two rings (upper right). ATP molecules occur in abundance in cell respiration, the chemical process which uses oxygen to oxidise sugars and fats to produce energy.