Which substance provides lubrication and acts as glue between cells in mucosal tissues?

• A. Mucin
• B. Collagen
• C. Keratin
• D. Elastin

Answer: (A)

Mucin is the glycoprotein component of mucus produced by goblet cells in mucosal epithelia. Its carbohydrate-rich side chains bind water, creating a hydrated, viscous gel that reduces friction between sliding mucosal surfaces. That gel also acts as a sticky coating, helping the epithelium stay cohesively lined and trapping debris, effectively providing a glue-like layer between cells in mucosal tissues. Collagen, keratin, and elastin are structural proteins: collagen adds tensile strength to connective tissue, keratin strengthens protective barriers in skin and nails, and elastin gives tissues elasticity. They don’t primarily provide lubrication or a lubricating glue on mucosal surfaces.