Question

What is true of membrane lipids and proteins?

• A. None can flip-flop
• B. Both can flip-flop
• C. Proteins can flip-flop but lipids cannot.
• D. Lipids flip-flop but proteins rarely flip-flop

Answer 1

The correct option is D Lipids flip-flop but proteins rarely flip-flop

Lipid bilayer of the cell membrane contains hydrophilic head groups facing outward and hydrophobic tails facing each other. The transport of phospholipids and lipid-linked oligosaccharides is difficult to achieve due to this bipolar nature. The transmembrane lipid transporter proteins called flippases transport lipids across cell membrane through transverse diffusion by flipping their orientation. Floppases transport in reverse direction. In mammals, this affects various processes such as blood coagulation, immune recognition, and programmed cell death.Most protein molecules do not flipflop due to their extensive polar regions, which are unfavorable in the hydrophobic core of the membrane.

Option D is correct.