A coupled reaction is a reaction with a common intermediate that results in energy being transferred from one side of the reaction to the other. A common example of a coupled reaction is the formation of ATP, a nucleotide that contains chemical energy that is broken down for metabolic uses.
ATP stores energy in the form of phosphate bonds. The energy is released when ATP is broken down into ADP. A few examples of the processes that use ATP include motility and cell division. ATP is also used as a substrate for kinases that phosphorylate proteins and lipids and by adenylate cyclase to produce cyclic AMP.