Membrane Fluidity Factors

Steps:

• Identify factors affecting phospholipid bilayer fluidity: chain length, saturation, and temperature.
• Shorter fatty acid chains increase fluidity by reducing van der Waals interactions.
• Unsaturated fatty acids (double bonds) increase fluidity by creating kinks that prevent tight packing.
• Higher temperatures increase fluidity by adding kinetic energy to phospholipids.
• Evaluate options: 1 likely longer chains (decreases fluidity), 2 unsaturated bonds (increases), 3 lower temperature (decreases).

Why D is correct:

• Only option 2 (unsaturated fatty acids) directly increases fluidity per fluid mosaic model, as double bonds disrupt packing.

Why the others are wrong:

• A includes all, but 1 and 3 decrease fluidity.
• B includes 1, which decreases fluidity via stronger interactions.
• C includes 3, which decreases fluidity by slowing molecular motion.

Final answer: D