The Cellular Currency: ATP (Adenosine Triphosphate)

Chemical structure of an ATP molecule. The adenine is phosphorylated with
3 phosphate groups. The bonds between phosphates are highly energetic.

ATP is a specific nucleotide. What makes ATP different from other nucleotides such as cytosine, thymine, guanine, and adenine, is that it is used widely as a carrier of chemical energy. ATP is adenine with three phosphate groups attached. The bond connecting the phosphate molecules to adenine are highly energetic bonds. Two of the phosphate groups, which are easily broken down to release energy, are added in a covalent bond during processes such as respiration. ATP is used to drive active transport, and other chemical reactions such as photosynthesis, and cellular respiration.

ATP is broken down by hydrolysis (reaction with water), which yields adenosine diphosphate (ADP), inorganic phosphorous, and energy. It can be broken down further into adenosine monophosphate (AMP), inorganic phosphorous and energy. The excess phosphorous yielded is later used to make more ATP from AMP.