Which of the following statements about membrane fluidity is correct?

• A. As temperature decreases, membrane fluidity decreases.
• B. As temperature increases, membrane fluidity decreases.
• C. As temperature decreases, membrane fluidity increases.
• D. Membrane fluidity is not affected by temperature changes.

Answer: (A)

Verified step by step guidance

1. Understand the concept of membrane fluidity: Membrane fluidity refers to the viscosity of the lipid bilayer of a cell membrane, which affects the movement of lipids and proteins within the membrane. It is influenced by factors such as temperature, lipid composition, and the presence of cholesterol.
2. Analyze the relationship between temperature and membrane fluidity: At higher temperatures, the kinetic energy of lipid molecules increases, causing them to move more freely and making the membrane more fluid. Conversely, at lower temperatures, lipid movement decreases, and the membrane becomes more rigid.
3. Consider the role of lipid composition: Saturated fatty acids (with no double bonds) pack tightly together, reducing fluidity, while unsaturated fatty acids (with one or more double bonds) create kinks in the hydrocarbon chains, preventing tight packing and increasing fluidity. Cholesterol also plays a role by stabilizing the membrane at high temperatures and preventing it from becoming too rigid at low temperatures.
4. Evaluate the given statements: Based on the relationship between temperature and membrane fluidity, the correct statement is that as temperature decreases, membrane fluidity decreases. This is because the lipid molecules move less at lower temperatures, leading to a more rigid membrane.
5. Conclude the reasoning: The other statements are incorrect because they either contradict the established relationship between temperature and fluidity or incorrectly claim that temperature has no effect on membrane fluidity.