Glycosaminoglycans and Glycoproteins

Comprehensive vocabulary flashcards covering the structure, composition, locations, and functions of glycosaminoglycans (GAGs), proteoglycans, and glycoproteins.

Glycosaminoglycans (GAGs)

Acidic heteropolysaccharides (mucopolysaccharides) with a high negative charge that bind $Na^+$ or $K^+$ to draw water osmotically, forming a gel-like matrix that provides a slippery consistency in mucous secretions and synovial fluid.

Chondroitin sulfate

The major glycosaminoglycan found in cartilage and bone, composed of repeating disaccharide units of D-Glucuronic Acid and N-Acetyl D-Galactosamine Sulfate.

Keratan sulfate

A glycosaminoglycan composed of D-Galactose and N-Acetyl sugar with sulfate on either sugar and no uronic acid; located in cartilage, loose connective tissue, and the cornea, where it maintains transparency.

L-Iduronic acid

The 5th epimer of D-Glucuronic Acid, present in both heparan sulfate and dermatan sulfate.

Heparan sulfate

A glycosaminoglycan composed of D-Glucosamine Disulfate and D-Glucuronic Acid sulfate (or L-Iduronic Acid sulfate) that functions in cell membrane receptors, cell-cell interactions, cell differentiation, tissue morphogenesis, and homeostasis.

Dermatan sulfate

A glycosaminoglycan composed of L-Iduronic Acid, D-Glucuronic Acid, and N-Acetyl-D-Galactosamine Sulfate, found in blood vessels, heart valves, skin, and sclera.

Hyaluronic acid

An unsulfated glycosaminoglycan composed of D-Glucuronic Acid and N-Acetyl D-Glucosamine, present in loose connective tissue and synovial fluid, functioning as a lubricant and shock absorber.

Proteoglycan monomer

A macromolecular structure consisting of a core protein covalently bonded to glycosaminoglycan chains, containing up to 95% carbohydrate.

Aggrecan

The aggregation of proteoglycan monomers non-covalently bound to hyaluronic acid via link proteins within a collagen meshwork to impart rigidity.

Glycoproteins

Proteins containing a polypeptide backbone covalently attached to one or several smaller, more diverse oligosaccharide side chains, consisting of 1–70% carbohydrate and 30–99% protein.

O-linked oligosaccharide

A carbohydrate chain covalently linked to the hydroxyl (-OH) group of serine or threonine residues in glycoproteins and proteoglycans.

N-linked oligosaccharide

An oligosaccharide chain covalently linked to the amino ($NH_2$) group of an asparagine residue.

Sialic acid

Also referred to as N-Acetylneuraminic acid (NANA), a sugar constituent found in glycoproteins.

L-Fucose

6-Deoxy L-Galactose, one of the primary sugar components found in glycoproteins.