Membrane adaptation using unsaturated fatty acids for ethanol tolerance

Steps:

• Ethanol disrupts membrane structure, increasing leakiness by altering fluidity.
• Replacing saturated fatty acid X with unsaturated Y introduces double bonds, which create kinks in lipid tails.
• These kinks prevent tight packing, maintaining membrane fluidity and stability against ethanol's effects.
• Increasing phospholipid proportion supports overall membrane integrity, but double bonds directly enhance stability.

Why B is correct:

• Unsaturated fatty acids with double bonds increase membrane fluidity per the fluid mosaic model, preventing rigidification or excessive disorder from ethanol, thus improving stability.

Why the others are wrong:

• A: Phospholipids do not increase "fluidity of ethanol" via channels; they form the bilayer for structural support.
• C: Shorter chains increase, not decrease, fluidity by reducing van der Waals interactions.
• D: Identical to C; shorter chains increase fluidity.

Final answer: B