Question

A mucopolysaccharide that functions as cell cement and lubricant is
A. Heparin
B. Hyaluronic acid
C. Keratan sulphate
D. Chondroitin sulphate

Answer 1

Hint:-Mucopolysaccharides are a group of compounds whose function is to lubricate and act as shock absorbers in the body. They are made up of repeated disaccharides or amino sugar units.

Complete answer:
Mucopolysaccharides, also known as glycosaminoglycans (GAG), are linear polysaccharide chains classified into four types: heparin, keratan sulphate, hyaluronic acid and chondroitin sulphate. They are synthesized in different parts of the body and possess different functions.
Heparin – It is synthesized in the golgi apparatus and rough endoplasmic reticulum (RER). Though heparin is widely used as anti-blood coagulant, its role when synthesized in the body is unclear. They are stored in mast cells and released to the site of infection as a defence mechanism against pathogens.
Hyaluronic acid – This non-sulfated GAG is produced by integral membrane synthases. It is a major component in extracellular matrix and is distributed across neural, epithelial and connective tissues. They enclose the cells in the body keeping them intact and act as lubricant facilitating movement of joints and muscles.
Keratan sulphate – These are secreted by the central nervous system and are found in cartilages, cornea and bones, as they are highly hydrated molecules. They aid in the formation of glial scars and act as shock absorbers in joints.
Chondroitin sulphate – Like heparin, chondroitin sulphate is also synthesized by golgi apparatus and RER. They are an integral component in cartilages and provide resistance to compression at the joints. They are used in the treatment of osteoarthritis.

Thus, the mucopolysaccharide that functions as lubricant and cell cement is (B) hyaluronic acid.


Note:- The mucopolysaccharides have varied sulfation, structure and molecular mass as they are synthesized by enzymes, unlike template synthesis as in the case of nucleic acids and proteins. The GAGs produced are broken down to maintain their levels in the body by enzymes. When they are not broken down, they get accumulated in the joints causing progressive cellular damage. This is a metabolic disorder known as Mucopolysaccharidosis.