Question

A lubricant, mucin in saliva is made up of?
A) Glycoproteins
B) Polysaccharides
C) Phospholipids
D) Myosin

Answer 1

Hint: Human salivary mucins are secreted through epithelial cells of the salivary glands of the oral cavity. Within the mouth, mucins coat the hard and soft tissues serving to lubricate and hydrate the oral structures.

Complete answer:
Glycoproteins (mucins) are the principal organic constituents of mucus, the slimy, viscoelastic material that envelopes all mucosal surfaces of the body. Oral dryness and the sensation of "burning", as well as difficulties with speaking, formation of a food bolus, and deglutition, which are known to accompany salivary hypofunction and lack of or qualitative change in salivary mucins. In addition, salivary mucins modulate the oral microflora by favouring attachment and subsequent proliferation of certain microorganisms and by promoting the clearance of others.

Based on macromolecular characteristics, the mucins in saliva fall into two categories: high (>1000 kDa) and low (200–300 kDa) molecular weight forms. The two forms, although differ with respect to bacterial clearance ability, display virtually identical carbohydrate chain make-up, ranging in size from 3 to 16 sugar units.

Polysaccharides are the polymers which contain repeating monosaccharide units. Starch is an example of polysaccharide which is broken by the salivary amylase.

Phospholipids- These are the lipid groups which contain phosphate groups. They are the structural component of the plasma membrane.

Myosin- These are present in the muscles. Myosin along with actin helps in muscle contraction.

Thus, the correct answer is option ‘A’ i.e, Glycoproteins.


Note: It is important to note that of the two mucin forms, the low molecular weight form more efficient in bacterial aggregation, predominates in saliva and oral mucosal mucus coat of caries-resistant individuals, while the level of the high molecular weight form is higher in caries-susceptible subjects.