Question 59:
Match List I with List II:
| List I: Animal Plasma Membrane | List II: Type of Sterol |
|---|---|
| A. Human myelin sheath | (iii) Cholesterol |
| B. Maize leaf | (iv) Stigmasterol |
| C. Yeast | (ii) Ergosterol |
| D. Paramecium | (i) Sitosterol |
Choose the correct answer from the options given below:
The correct answer is (C) (A) – (III), (B) – (IV), (C) – (II), (D) – (I).
Human myelin sheath primarily contains cholesterol, maize leaf membranes feature stigmasterol as a major plant sterol, yeast plasma membranes are enriched in ergosterol, and Paramecium employs sitosterol in its membranes.
Option Breakdown
(A) (A)-(i) Sitosterol, (B)-(iii) Cholesterol, (C)-(ii) Ergosterol, (D)-(iv) Stigmasterol
Incorrect; assigns mammalian cholesterol to plant maize and swaps Paramecium’s sitosterol with animal myelin.
(B) (A)-(ii) Ergosterol, (B)-(iv) Stigmasterol, (C)-(i) Sitosterol, (D)-(iii) Cholesterol
Wrong; places fungal ergosterol in human myelin and protozoan sitosterol in yeast.
(C) (A)-(iii) Cholesterol, (B)-(iv) Stigmasterol, (C)-(ii) Ergosterol, (D)-(i) Sitosterol
Correct; matches kingdom-specific sterols: animals cholesterol, plants stigmasterol/sitosterol, fungi ergosterol, protists like Paramecium sitosterol.
(D) (A)-(iv) Stigmasterol, (B)-(ii) Ergosterol, (C)-(i) Sitosterol, (D)-(iii) Cholesterol
No; confuses plant stigmasterol with human myelin and fungal ergosterol with maize.
Introduction to Animal Plasma Membrane Sterol
Animal plasma membrane sterol varies by organism: cholesterol dominates human myelin, stigmasterol maize leaves, ergosterol yeast, sitosterol Paramecium. GATE Life Sciences tests this evolutionary adaptation.
Sterol Roles Across Organisms
Sterols modulate membrane fluidity; cholesterol (~40% myelin) forms lipid rafts, stigmasterol (~20-30% plant PM), ergosterol yeast PM (up to 30%), β-sitosterol/ stigmasterol in protozoa like Paramecium for order.
Biosynthesized from squalene, kingdom-specific modifications.
Correct Matching Table
| Category | Sterol | Key Location [Source] |
|---|---|---|
| Human Myelin | Cholesterol (iii) | Animal membranes |
| Maize Leaf | Stigmasterol (iv) | Plant PM |
| Yeast | Ergosterol (ii) | Fungal PM |
| Paramecium | Sitosterol (i) | Protist membranes |
Option C nails animal plasma membrane sterol pairings.
Exam Tips for Life Sciences
Builds on prior lipids (glycerophospholipids, prenols); recall fungi=ergosterol, plants=sitosterol/stigmasterol, animals=cholesterol for PYQs.
