Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Glycosamino glycans are having characteristically high negative charge in nature
Reason (R): Glycosaminoglycans are made up of alternating units of uronic acids and amino sugar with sulfated ester.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Sulfate groups (\(-SO_3^-\)) and carboxyl groups (\(-COO^-\)) on the repeating disaccharide sugars of GAGs carry strong negative charges.
This electrostatic repulsion gives GAGs their highly hydrated, lubricating physical properties.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Glycosaminoglycans (GAGs), also known as mucopolysaccharides, are long, unbranched polysaccharides consisting of repeating disaccharide units.

Step 2: Detailed Explanation:
- Assertion (A) evaluation: GAGs have the highest density of negative charge of any known biological macromolecule. This is a true statement.
- Reason (R) evaluation: The repeating disaccharide unit of a GAG consists of an amino sugar (D-glucosamine or D-galactosamine) and an acidic sugar (uronic acid, such as D-glucuronic acid or L-iduronic acid). In most GAGs, the hydroxyl groups of the sugars are covalently modified with sulfate groups (forming sulfated esters). This is a true statement.
- Explanation check: The carboxyl groups of the uronic acids and the sulfate ester groups on the amino sugars are highly deprotonated at physiological pH, carrying negative charges. This specific chemical structure is the direct cause of the characteristically high negative charge density of GAGs. Thus, (R) is the correct explanation of (A).

Step 3: Final Answer:
Both (A) and (R) are true and (R) is the correct explanation of (A). This corresponds to option (A).