Pentoses are carbohydrates made of five carbons.

The DNA molecule is made of a sequence of molecules called nucleotides. Each nucleotide is formed by the association of one pentose called deoxyribose with a phosphoric acid and a nitrogen-containing base (A, T, C or G). RNA is also formed by a sequence of nucleotides. The RNA nucleotides are made by association of one ribose (a pentose) with one phosphoric acid and one nitrogen-containing base (A, U, C or G).

So pentoses are fundamental components of DNA and RNA.