Complex carbohydrates

Complex carbohydrates

Sugars may be linked to other types of biological molecules to form glycoconjugates. The enzymatic process of glycosylation creates sugars that are bonded to other types of molecules such as proteins and lipids by the glycosidic bond. The bound sugar or polysaccharide is called a glycan (a free glycan if it is unbound). Glycoproteins, proteoglycans and glycolipids are the most abundant glycoconjugates found in mammalian cells. They are found predominantly on the outer cell membrane and in secreted fluids. Glycoconjugates have been shown to be important in cell-cell interactions due to the presence on the cell surface of various glycan binding receptors in addition to the glycoconjugates themselves. In addition to their function in protein folding and cellular attachment, the N-linked glycans of a protein can modulate the protein's function, in some cases acting as an on-off switch.