Q.5 Which of the are components of lipid raft in plasma membrane?
A. Cholesterol
B. Sphingolipids
C. Glycolipids
D. Phospholipids
Choose the conect answer from the options given below:
I. (A) and (B) only
2. (A) and (C) only
3. (B) and (C) only
4. (C) and (D) only
Answer: Option 1 ((A) and (B) only, ID: 68019147817).
Lipid rafts are ordered microdomains in the plasma membrane enriched in cholesterol and sphingolipids, which provide structural integrity and facilitate signaling.
Option Analysis
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A. Cholesterol: Core component that acts as “glue,” filling spaces between sphingolipid chains to promote tight packing and phase separation from fluid membrane regions.
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B. Sphingolipids: Major raft lipids (e.g., sphingomyelin) with long, saturated acyl chains that enable ordered gel-like state; primarily in outer leaflet.
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C. Glycolipids: Present in some rafts but not defining components; minor role compared to sphingolipids and cholesterol.
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D. Phospholipids: Abundant in surrounding fluid bilayer but excluded from rafts due to unsaturated chains causing disorder.
Correct Choice Breakdown
| Option | Components | Correct? | Reason |
|---|---|---|---|
| 1 | Cholesterol, Sphingolipids | Yes | Classic raft definition |
| 2 | Cholesterol, Glycolipids | No | Glycolipids secondary |
| 3 | Sphingolipids, Glycolipids | No | Lacks cholesterol |
| 4 | Glycolipids, Phospholipids | No | Neither primary raft lipids |
Lipid raft components plasma membrane form specialized microdomains crucial for cell signaling and membrane organization in GATE Life Sciences syllabus. These cholesterol and sphingolipid-enriched regions exclude phospholipids, enabling protein clustering.
Core Lipid Raft Components
Cholesterol (30-50% of raft mass) stabilizes sphingolipids’ saturated chains, creating liquid-ordered (Lo) phase distinct from liquid-disordered (Ld) bilayer. Sphingomyelin, a key sphingolipid, resists detergent extraction—classic raft assay marker.
Why Not Glycolipids or Phospholipids?
Glycolipids contribute minimally; phospholipids’ cis-unsaturations disrupt raft order. Rafts (~10-200 nm) host GPI-anchored proteins, receptors for signal transduction.
Biological Role Table
| Component | Raft Property | Function Example |
|---|---|---|
| Cholesterol | Phase separation | Caveolae formation |
| Sphingolipids | Ordered packing | Pathogen entry portals |
| Glycolipids | Accessory | Limited signaling role |
| Phospholipids | Excluded | Form fluid bilayer |
Mastering lipid raft components plasma membrane aids molecular biology and microbiology prep—key for competitive exams.
