Which of the following is an example of a glycoprotein?

• A. Hemoglobin
• B. Collagen
• C. Mucin and saliva
• D. Myosin

Answer: (C)

Glycoproteins are proteins with carbohydrate chains covalently attached. In saliva, mucins are classic glycoproteins because their long sugar chains give mucus its gel-like, lubricating properties and help protect the oral surfaces. Hemoglobin is a protein but not typically glycosylated in a way that defines a glycoprotein. Collagen is a structural protein with some carbohydrate residues, but it is not classified primarily as a glycoprotein. Myosin is a motor protein and is not defined by glycosylation related to mucus; it serves contractile functions rather than lubrication. Therefore, the example that fits as a glycoprotein is mucin and saliva.