Nucleoside monophosphate

A nucleoside monophosphate is a nucleotide with one phosphate group attached to a nucleoside. The nucleoside supplies a nucleobase linked to a sugar; the monophosphate specifies the phosphate count. Attachment position and sugar identity still matter. A common example is adenosine monophosphate, with a phosphate ester at the 5′ position of ribose; ChEBI identifies it specifically as adenosine 5′-monophosphate.^[ref]

The corresponding acid structure has molecular formula ${\mathrm{C}}_{10}{\mathrm{H}}_{14}{\mathrm{N}}_5{\mathrm{O}}_7\mathrm{P}$. Its single phosphorus atom provides a quick count, but the chemical structure is what identifies the 5′ attachment. The neutral acid formula is a stated representation; proton loss changes charge and hydrogen count without adding a second phosphate group.^[ref] A nucleoside diphosphate instead contains a linked pair of phosphate groups.

A useful reaction is the adenylate kinase interconversionwhere the abbreviations denote adenosine triphosphate, adenosine monophosphate and adenosine diphosphate. The phosphate-unit balance is $3+1=2+2$: a phosphate group is transferred rather than created.^[ref]

For an original reaction-extent example, start with $0.5\mathrm{mmol}$ of ATP, $0.3\mathrm{mmol}$ of AMP and no ADP. A forward extent of $0.2\mathrm{mmol}$ leaves $0.3\mathrm{mmol}$ ATP, $0.1\mathrm{mmol}$ AMP and produces $0.4\mathrm{mmol}$ ADP. Both sides of this bookkeeping contain $1.8\mathrm{mmol}$ of phosphate units. This is a stoichiometry calculation for a specified extent, not a prediction of chemical equilibrium.