All the following processes occur rapidly in the membrane lipid bilayer except

The process that does not occur rapidly in the membrane lipid bilayer is:

(C) Transbilayer diffusion of phospholipids (also known as “flip-flop”).

This process is slow because it requires phospholipids to move from one bilayer leaflet to the other, which is energetically unfavorable.

The correct answer is (C) Transbilayer diffusion of phospholipids.

Here’s why:

– (A) Flexing of fatty acyl chains: This occurs rapidly due to the fluid nature of the lipid bilayer, allowing for constant motion and flexibility.
– (B) Lateral diffusion of phospholipids: Phospholipids can move laterally within the bilayer quickly, allowing for rapid changes in membrane composition and structure.
– (D) Rotation of phospholipids around their long axes: This also occurs rapidly, enabling phospholipids to change their orientation and position within the bilayer.