Nucleotides are low molecular weight compounds that have three characteristic components:

• A 5-carbon sugar or pentose (deoxyribose for DNA formation, ribose for RNA formation).
• A nitrogenous base (purine or pyrimidine bases) linked by a glycosidic bond to the pentose.
• Phosphate groups linked by phosphodiester bonds.

Being part of nucleic acids, nucleotides perform a wide variety of functions in the cell.

In breast milk the predominant nucleosides are cytidine and uridine, basic micronutrients. The predominant nucleotide is cytidine diphosphate, followed by cytidine monophosphate, inosine monophosphate, and uridine monophosphate.