The mucopolysaccharide serves as a lubricant and shock absorbent in joints:

Appeared in: NVS- 2025

Explanation

Hyaluronic acid is a major glycosaminoglycan (GAG) found in the synovial fluid of joints.
Its structure consists of long, unbranched chains of repeating disaccharide units (glucuronic acid and N-acetylglucosamine).
This structure allows it to attract and retain large volumes of water, creating a highly viscous, gel-like fluid.
This viscosity is essential for lubricating the articular cartilage surfaces, reducing friction during movement.
The water-binding capacity provides excellent shock absorption, protecting the joint from mechanical stress.

Option A: Dermatan sulfate is primarily a structural component of skin, blood vessels, and heart valves, not a joint lubricant.
Option B: While keratan sulfate is found in cartilage, it is a structural part of the cartilage matrix itself, not the primary lubricant in the synovial fluid.
Option D: Heparin's primary and well-known function is as a potent anticoagulant to prevent blood clotting.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Biochemical functions of mucopolysaccharides (glycosaminoglycans) as background academic context rather than a clinical decision trigger.
In osteoarthritis, the concentration and molecular weight of hyaluronic acid in the synovial fluid decrease, leading to loss of viscosity, increased friction, and joint pain.
This knowledge is the basis for viscosupplementation, a treatment where hyaluronic acid is injected directly into the joint (intra-articular injection) to restore lubrication and reduce pain.
What if? If a patient has a condition causing excessive blood clotting, a substance related to one of the distractors (Heparin) would be used therapeutically, highlighting the very different roles of these molecules.

How to Approach the Question

First, identify the key terms in the question: 'mucopolysaccharide', 'lubricant', 'shock absorbent', and 'joints'.
The question asks for a specific function (lubrication/shock absorption) in a specific location (joints).
Systematically review the function of each option.
Recall or deduce that Heparin is an anticoagulant, immediately eliminating it.
Differentiate between the GAGs found in connective tissues. While several are in cartilage (Keratan sulfate, Chondroitin sulfate), Hyaluronic acid is uniquely dominant in the synovial fluid for lubrication.
Select Hyaluronic acid as it is the only option whose primary role matches the function and location described in the question.

Concept Tested & Keywords

Concept Tested: Biochemical functions of mucopolysaccharides (glycosaminoglycans)
Stem keywords: mucopolysaccharide, lubricant, shock absorbent, joints
Lead-in keywords: BEST, MOST RELEVANT CLUE

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) pp. 592-594, 593-595, 594-596

Practise the full NVS- 2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.