Proteoglycan

A molecule consisting of a core protein attached to one or more glycosaminoglycan chains. Proteoglycans are major components of the extracellular matrix and help shape its structure and interactions.

Glycosaminoglycan: A long, linear polysaccharide made of repeating disaccharide units, often bearing sulfate groups. These chains are the defining carbohydrate components attached to a proteoglycan’s core protein.
Extracellular matrix: The network of molecules surrounding cells that provides structural support and biochemical cues. Proteoglycans are major matrix components, shaping its physical properties and molecular interactions.
Aggrecan: A large cartilage proteoglycan bearing many chondroitin sulfate and keratan sulfate chains. Its dense chains retain water and help cartilage withstand compression.
Osteoarthritis: A degenerative joint disease involving cartilage damage, bone changes, and joint symptoms. Loss and breakdown of cartilage aggrecan weaken the tissue’s resistance to compression.
Core protein: The protein backbone to which one or more glycosaminoglycan chains are covalently attached. It provides the scaffold that distinguishes each proteoglycan and organizes its attached chains.
Osmotic pressure: The pressure difference that drives water across a semipermeable membrane because of solute concentration differences. Charged glycosaminoglycan chains draw in water, helping proteoglycan-rich tissues resist compression.
Decorin: A small leucine-rich proteoglycan that binds collagen fibrils in connective tissues. It regulates collagen fibril organization and links proteoglycans to tissue architecture.
Mucopolysaccharidosis: A group of inherited lysosomal storage disorders caused by impaired glycosaminoglycan degradation. Undegraded glycosaminoglycans accumulate in cells and disrupt organ function.
Chondroitin sulfate: A sulfated glycosaminoglycan composed of repeating glucuronic acid and N-acetylgalactosamine units. It is a common chain type whose charge and length shape proteoglycan behavior.
Electrostatic interaction: An attractive or repulsive force between particles arising from their electric charges. Sulfate and carboxyl groups let proteoglycans bind or repel charged molecules.

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