Which of the following makeup of cellular membranes would be most likely best suited to HOT temperatures?

Question

BlackTom AI · Accepted Answer

Membrane fluidity is determined primarily by the degree of fatty-acid saturation and the amount of cholesterol in the bilayer, so these factors control how a membrane responds to high temperature.

1) Relevant knowledge points and concepts
- Saturated fatty acids have straight hydrocarbon chains that pack tightly, decreasing fluidity; unsaturated fatty acids have cis double bonds that introduce kinks, increasing fluidity. 
- Temperature increases kinetic energy of lipid molecules, increasing membrane fluidity. 
- Cholesterol acts as a fluidity buffer: at high temperatures it restrains movement of phospholipids and decreases fluidity, while at low temperatures it prevents tight packing and thus increases fluidity. 
- Homeoviscous adaptation: organisms adjust lipid composition to maintain optimal membrane viscosity under different temperatures.

2) Step-by-step reasoning
- High ambient temperature → lipids gain kinetic energy → bilayer becomes more fluid and potentially leaky. 
- To counteract excess fluidity, membranes must reduce inherent fluidity by (a) increasing saturated fatty acids (tighter packing) and (b) increasing cholesterol (which fills gaps and restricts lateral movement at high T). 
- Therefore a membrane best suited for hot temperatures will be enriched in saturated fatty acids and cholesterol to maintain integrity.

3) Calculations
- No numeric calculations are required; this is qualitative physical chemistry/biochemistry reasoning.

4) Why the correct answer is correct
- Option d (higher proportion of saturated fatty acids and cholesterol) directly reduces fluidity and stabilizes the membrane at elevated temperatures, preventing excessive permeability and loss of function.

5) Why other options are incorrect
- a (more unsaturated) would increase fluidity—bad at high T. 
- b (more saturated only) helps but lacks cholesterol’s additional stabilizing effect. 
- c (unsaturated + cholesterol) still includes unsaturated tails that raise baseline fluidity, counterproductive in heat.

Conclusion: The best membrane composition for hot temperatures is d. A higher proportion of saturated fatty acids and cholesterol.

Which of the following makeup of cellular membranes would be most likely best suited to HOT temperatures?单项选择题

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