The heteropolysaccharide that acts as a lubricant and shock absorber in joints is?

DSSSB - 28 August 2019 (Shift-1)

Biochemistry & Nutrition

Easy

Appeared in: DSSSB - 28 August 2019 (Shift-1)

Explanation

Hyaluronic acid is a large, unbranched heteropolysaccharide, specifically a type of glycosaminoglycan (GAG).
It is a primary and essential component of synovial fluid, which fills the cavity of synovial joints.
Its unique molecular structure allows it to bind large quantities of water, giving synovial fluid its high viscosity (thickness).
This viscosity is critical for its function as a lubricant, reducing friction between the articular cartilage during movement.
It also serves as a shock absorber by resisting compressive forces, protecting the joint from impact during activities like walking or running.

Option B: Heparin is a heteropolysaccharide (a GAG), but its primary function is as a natural anticoagulant to prevent blood clotting. It does not serve as a lubricant in joints.
Option C: Cellulose is a structural homopolysaccharide found in plant cell walls. Humans cannot digest it, and it functions as dietary fiber. It is not produced or found in human joints.
Option D: Glycogen is a branched homopolysaccharide used for energy storage in animals, primarily in the liver and muscles. It is not a heteropolysaccharide and has no structural or lubricating role in joints.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Biochemical functions of polysaccharides in the human body, specifically in relation to joint structure and function as background academic context rather than a clinical decision trigger.
Nurses often educate patients with osteoarthritis about treatments like viscosupplementation, which involves injecting hyaluronic acid directly into the joint to restore lubrication and reduce pain.
Understanding the function of hyaluronic acid is key to explaining the pathophysiology of degenerative joint diseases and the rationale behind certain treatments.
A decrease in the quality or quantity of hyaluronic acid in synovial fluid is a hallmark of osteoarthritis, leading to increased friction, inflammation, and pain.

How to Approach the Question

First, break down the question's key terms: 'heteropolysaccharide', 'lubricant', 'shock absorber', and 'joints'.
The term 'heteropolysaccharide' (made of different sugar units) helps eliminate options. Recall that glycogen and cellulose are 'homopolysaccharides' (made of only glucose). This narrows the choices to Hyaluronic acid and Heparin.
Next, focus on the function: 'lubricant and shock absorber in joints'.
Evaluate the remaining options. Heparin is famous as an anticoagulant (blood thinner). Hyaluronic acid is a well-known component of connective tissue and synovial fluid.
Connect the function to the location. Synovial fluid in joints provides lubrication. Therefore, the substance responsible must be a key component of this fluid.
Conclude that Hyaluronic acid is the only option that is a heteropolysaccharide and performs the specified functions in joints.

Concept Tested & Keywords

Concept Tested: Biochemical functions of polysaccharides in the human body, specifically in relation to joint structure and function.
Stem keywords: heteropolysaccharide, lubricant, shock absorber, joints
Lead-in keywords: is
Clinical cues: The context of joints points towards a substance found in synovial fluid.

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