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 β-1,4-linked D-glucose, and chitin is a glycan composed of β-1,4-linked N-acetyl-D-glucosamine. Glycans can be homo- or heteropolymers of monosaccharide residues, and can be linear or branched.
Glycans can be found attached to proteins as in glycoproteins and proteoglycans. In general, they are found on the exterior surface of cells. O- and N-linked glycans are very common in eukaryotes but may also be found, although less commonly, in prokaryotes.
In a brand new place, brand new life
Brand new line between what's wrong and what's right
And now you're messing 'round with something new
What do you expect me to do? 'Cause you're
Playing with fire (Don't know what to do) Well you're
Playing with fire (You look like a fool) You're
Playing with fire (Don't know which way's up or down)
Don't come running to me when you hit the ground
From the farthest shores to the nearest seas
From the places you go 'till the people you meet
And now you're messing 'round with someone new
What do you expect me to do? 'Cause you're
Playing with fire (Don't know what to do) Well you're
Playing with fire (You look like a fool) You're
Playing with fire (Don't know which way's up or down)