Question

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how does lipid composition affect membrane fluidity?

☐ sphingolipids tend to make the membrane less fluid.

☐ saturated fatty acids tend to make the membrane less fluid because they pack together well.

☐ lipid composition has no effect on the fluidity of membranes.

☐ unsaturated fatty acids tend to make the membrane less fluid because kinks introduced by the double bonds keep them from packing together well.

Explanation:

1. Sphingolipids: Sphingolipids have more rigid structures compared to some other lipids, so they tend to reduce membrane fluidity. So this statement is correct.
2. Saturated fatty acids: Saturated fatty acids have straight chains, allowing them to pack closely together, which decreases membrane fluidity. This statement is correct.
3. Lipid composition effect: Lipid composition does affect membrane fluidity (e.g., types of fatty acids, presence of sphingolipids/cholesterol), so this statement is incorrect.
4. Unsaturated fatty acids: Unsaturated fatty acids have double bonds that introduce kinks, preventing tight packing and actually increasing membrane fluidity (not less fluid). So this statement is incorrect.

Answer:

A. Sphingolipids tend to make the membrane less fluid.
B. Saturated fatty acids tend to make the membrane less fluid because they pack together well.