Question

According to the most accepted model (fluid mosaic model) of Singer and Nicolson (1972), which one is wrong?

• A. Lateral diffusion of proteins in phospholipid bilayer is possible
• B. Generally, 52% of proteins and 40% lipids are present in the membrane of human cells
• C. Peripheral proteins lie on the surface of membrane while the integral proteins are partially or totally buried in the membrane
• D. Cellular membranes act only as semi permeable boundary

Answer 1

The correct option is D Cellular membranes act only as semi permeable boundary

The structure of cell membrane was proposed by Singer and Nicolson (1972). According to this, the cell membrane is semipermeable (or selectively permeable) for some molecules but many molecules can also move freely across the membrane. The quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer. Membrane proteins can be classified as integral or peripheral. Peripheral proteins lie on the surface of membrane while the integral proteins are partially or totally buried in the membrane. Generally, 52% of proteins and 40% lipids are present in the membrane of human cells.