גליקוזאמינוגליקנים

Glycosaminoglycans or GAGs are linear polymers of specific repeating disaccharides - the amino sugar N-acetylglucosamine or N-acetylgalactosamine, and the other is usually a uronic acid that can be glucuronic acid or iduronic acid.

Four main groups of GAGs are hyaluronan, chondroitin, and dermatan sulfate, heparan sulfate, and keratan sulfate, based on the sugar, the type of linkage between the sugars, and the number and location of sulfate groups.

Because of the sugar-bound sulfate and carboxylic groups, GAGs are highly acidic, bearing a negative charge.

So, the GAGs present in the extracellular space of the connective tissue attract clouds of cations like sodium ions. As a result, water is sucked into the matrix. This creates a swelling or turgor pressure helping the matrix withstand compressive forces.

Most GAGs are covalently attached to a core protein forming proteoglycan. In the cartilage matrix, these proteoglycans are linked to hyaluronic acid, a non-sulfated GAG, forming proteoglycan aggregates, which provide load-bearing capacity and resistance to deformity.