Pyrimidines are heterocyclic six-membered nitrogen-containing carbon ring structures with uracil cytosine and thymine being the basal structures of ribose-containing nucleosides (uridine cytidine and thymidine respectively) or deoxyribose-containing deoxynucleosides and their corresponding ribonucleotides or deoxyribonucleotides.

The seeds of Daucus carota.

N-Acetyl-d-galactosamine (GalNAc) is a terminal essential amino sugar derived from galactose and forms the antigens of blood group A in humans.