- Not to be confused with glucan.
The terms
glycan and
polysaccharide are defined by
IUPAC as synonyms meaning "compounds consisting of a large number of
monosaccharides linked glycosidically". However, in practice the term glycan may also be used to refer to the
carbohydrate portion of a
glycoconjugate, such as a
glycoprotein,
glycolipid, or a
proteoglycan, even if the carbohydrate is only an
oligosaccharide. Glycans usually consist solely of
O-glycosidic linkages of monosaccharides. For example, cellulose is a glycan (or, to be more specific, a
glucan) composed of ß-1,4-linked
D-glucose, and chitin is a glycan composed of ß-1,4-linked
N-acetyl-
D-glucosamine. Glycans can be homo- or heteropolymers of monosaccharide residues, and can be linear or branched.