Phosphodiester bond

The nucleotides are linked to form a chain through the phosphodiester bond.

Phosphodiester bond in a phospholipid

Phosphodiester bonds form the cohesion in the backbone of DNA and RNA . The nucleotides from which these are built up initially only have a phosphoric acid residue on carbon atom C5 of the underlying pentose , which chemically represents an ester of phosphoric acid with the alcoholic OH group on this carbon atom. In the case of chain lengthening in the course of transcription of the RNA or replicationthe DNA, starting from the phosphoric acid residue present, closes a second ester bond with the OH group on carbon atom C3 of ribose or deoxyribose , which creates the 3'-5'-phosphodiester bond.