According to widely accepted "fluid mosaic model" cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statements is incorrect ?
- Proteins in cell membranes can travel within the lipid bilayer
- Proteins can also undergo flip-flop movements in the lipid bilayer
- Proteins can remain confined within certain domains of the membranes
- Many proteins remain completely embedded within the lipid bilayer
Answer
(2) Proteins can also undergo flip-flop movements in the lipid bilayer
Solution
As per NCERT, according to the fluid mosaic model the quasi-fluid nature of lipids enables lateral movement of proteins within the overall bilayer.
So proteins can move laterally, some remain confined within certain membrane domains, and many integral proteins are embedded in the bilayer.
Flip-flop (transverse movement from one face of the bilayer to the other) occurs rarely in lipids, but not in proteins, because their large hydrophilic parts cannot pass through the hydrophobic core.
∴ The incorrect statement is that proteins can undergo flip-flop movements.
Answer: (2)