Glycosaminoglycans and Proteoglycans – Video Notes

Vocabulary flashcards covering key glycosaminoglycans (GAGs), proteoglycans, and their roles in connective tissues and ocular structures.

Glycosaminoglycans (GAGs)

Long, unbranched polysaccharides consisting of repeating disaccharide units, often sulfated, that form proteoglycans in the extracellular matrix and provide lubrication, hydration, and resistance to compression.

Disaccharide repeating unit

The basic repeating unit of a GAG; typically a sulfated pair of sugars, usually an amino sugar (N-acetylglucosamine or N-acetylgalactosamine) and a uronic acid (glucuronic or iduronic acid), with variable sulfation.

Hyaluronic acid (hyaluronan)

A large, non-sulfated GAG that forms proteoglycan aggregates; acts as a lubricant and shock absorber in joints and the eye, found in synovial fluid, vitreous humor, umbilical cord, and connective tissues; not covalently attached to a core protein.

Hyaluronidase

Enzyme that hydrolyzes hyaluronic acid; produced by certain bacteria and tissues; increases tissue permeability and facilitates spread of infection.

Chondroitin sulfate

GAG with repeating disaccharide units of glucuronic or iduronic acid and N-acetylgalactosamine; sulfated at positions 4 or 6; major component of cartilage providing resistance to compression.

Dermatan sulfate

GAG composed of iduronic acid and N-acetylgalactosamine; sulfated; found in skin and blood vessels; involved in wound healing and coagulation.

Keratan sulfate

GAG found in cornea, cartilage, and brain; sulfated; component of proteoglycans; present in heart valves and vessels; interacts with cell surfaces.

Heparan sulfate

GAG present in basement membranes and on cell surfaces; binds growth factors and lipoproteins; participates in cell signaling and development; highly sulfated.

Heparin

A highly sulfated form of heparan sulfate used clinically as an anticoagulant; derived from mast cells; inhibits thrombin and factor Xa.

Proteoglycan

Core protein with covalently attached GAG chains; forms aggregates in the extracellular matrix; provides structural support, hydration, and lubrication (e.g., in cartilage).

Vitreous humor

Gel-like substance in the eyeball containing hyaluronic acid and proteoglycans; helps maintain eye shape and optical properties.

Lubricant and shock absorber (function of GAGs/ proteoglycans)

GAGs and proteoglycans retain water and form hydrated gels that lubricate joints and absorb shocks in connective tissue.