Epithelial mucins include which type of molecules?

• A. Glycoproteins
• B. Hyaluronic acid
• C. Chondroitin sulfate
• D. Keratan sulfate

Answer: (A)

Epithelial mucins are glycoproteins. They are large protein molecules with extensive carbohydrate attachments, mainly O-linked glycans on serine and threonine residues. This heavy glycosylation gives mucins their high molecular weight and the viscous, gel-like quality of mucus that protects and lubricates epithelial surfaces. The other substances listed are glycosaminoglycans (hyaluronic acid, chondroitin sulfate, keratan sulfate), which are carbohydrate polymers found in the extracellular matrix and do not make up mucins. So, epithelial mucins are best described as glycoproteins.