A figure shows a section of a cell membrane: a double layer of lipid molecules with their round polar heads (A) facing the two outer sides and their tails (B) pointing inward. Some proteins (C) pass right through the double layer, and others (D) sit only on its surface. Which statement about this figure is correct?
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In the fluid mosaic model, lipids form a bilayer with polar heads outside and hydrophobic tails inside. Integral proteins are buried in it and peripheral proteins lie on its surface. The quasi-fluid nature of the lipid layer allows proteins to move laterally.
- A.
The tails are hydrophobic and point to the inner part of the bilayer. The polar heads face the two outer sides.
- C.
Proteins lying on the surface are peripheral proteins. Integral proteins are partially or totally buried in the membrane, like C.
- D.
It is the other way round: the erythrocyte membrane has about 52 per cent protein and 40 per cent lipid.
NCERT: Class 11 Biology, Chapter 8