Question

What are proteoglycans? What are they composed of? What roles do they serve?

Answer 1

Defination : Proteoglycans which are allso called mucoproteins are profusely glycosylated proteins that are normally found in connective tissues, extracellular matrix (ECM) and on the surfaces of most of the cells.

Composition : Proteoglycans are macromolecules of the cell surface or extracellular matrix in which one or more
glycosaminoglycan chains are joined covalently to a membrane protein/  The basic proteoglycan unit consists of a "core protein" along with covalently attached glycosaminoglycan (GAG) chain(s).

GAGs are long unbranched polysaccharides consisting of a repeating disaccharide unit. These units consists of an amino sugar (N-acetylglucosamine or N-acetylgalactosamine) along with a uronic sugar (glucuronic acid or iduronic acid) or galactose.

Functions :

Proteoglycans are a major component of the animal extracellular matrix.

Involved in binding cations such as sodium, potassium and calcium and water, and

also regulates the movement of molecules through the matrix.