Correct option is C
Membrane fluidity refers to how easily lipids and proteins move within the lipid bilayer. Several factors influence membrane fluidity, including lipid composition, temperature, and cholesterol content.
i. Monomeric G-proteins
Incorrect – Does NOT influence membrane fluidity
- Monomeric G-proteins (e.g., Ras, Rab) are signaling molecules that associate with membranes but do not alter membrane structure or fluidity.
- Their activity affects cell signaling rather than membrane fluidity.
ii. Peripheral membrane proteins
Incorrect – Does NOT significantly influence membrane fluidity
- Peripheral proteins attach to the membrane surface without embedding into the bilayer.
- Since they do not disrupt lipid packing, they have minimal influence on membrane fluidity.
iii. Sphingolipids
Correct – Influences membrane fluidity
- Sphingolipids (e.g., sphingomyelin, glycosphingolipids) are major components of lipid rafts, which create rigid, less fluid membrane regions.
- High sphingolipid content reduces membrane fluidity by increasing lipid packing.
iv. Phospholipid sidechain saturation
Correct – Influences membrane fluidity
- Saturated phospholipids (no double bonds) reduce fluidity because they pack tightly.
- Unsaturated phospholipids (with double bonds) increase fluidity by preventing tight packing.
- This factor is crucial in regulating membrane flexibility in different temperature conditions.
v. Cholesterol
Correct – Influences membrane fluidity
- At high temperatures, cholesterol reduces fluidity by stabilizing the membrane.
- At low temperatures, cholesterol prevents solidification by disrupting lipid packing, maintaining fluidity.
- Overall, cholesterol acts as a fluidity buffer.
Information Booster:
Factors Affecting Membrane Fluidity:
Lipid Composition:
- More saturated fatty acids → Less fluidity.
- More unsaturated fatty acids → More fluidity.
Cholesterol:
- Acts as a fluidity buffer, preventing extreme changes in membrane fluidity.
Temperature:
- Higher temperatures → Increases fluidity.
- Lower temperatures → Decreases fluidity.
Lipid Rafts (Sphingolipids & Cholesterol):
- Create less fluid, more ordered membrane regions important for cell signaling.
