adenosine monophosphate (AMP), organic compound composed of an adenine base, the sugar ribose, and one phosphate unit. AMP is one of the possible products of the hydrolysis of adenosine triphosphate (ATP) and is therefore important in the transfer of chemical energy during anabolism. Cyclic AMP, a very close structural relative of AMP containing an additional ester linkage between the phosphate and ribose units, can act as a secondary messenger for several hormones. It also plays a role in the transcription of some genes (see nucleic acid).