Question

Keeping in view the 'fluid mosaic model' for the structure of cell membrane, which one of the following statement is correct with respect to the movements of lipids and proteins from one lipid monolayer to the other (described as flipflop movement)?

• A. while proteins can flip-flop, lipids can not
• B. neither lipids, nor proteins can flip-flop
• C. both lipids and proteins can flip-flop
• D. while lipids can rarely flip-flop

Answer 1

Answer: (D)

while lipids can rarely flip-flop

Answer 2

According to fluid mosaic model there is rapid internal motion involving flexing within each lipid molecule a rapid lateral diffusion of the lipids is possible and a slow 'flip-flop' motion, i.e., a transfer of lipid molecules from one side of the bilayer to the other, is also possible. The lipid molecules might also rotate about their axes. The proteins of the membrane are concerned with the enzymatic activity of the membrane, with transport of molecules, and with a receptor function whereas, the lipid bilayer provides the permeability barrier.