Which type of substance would face difficulty to pass through the cell membrane?
- Substance soluble in lipids
- Substance with hydrophobic moiety
- Substance with hydrophilic moiety
- All substances irrespective of hydrophobic and hydrophilic moiety
Answer
(3) Substance with hydrophilic moiety
Solution
The cell membrane is a lipid bilayer whose interior is formed by the non-polar (hydrophobic) tails of the lipids.
∴ Lipid-soluble substances (hydrophobic moiety) pass through it easily by simple diffusion.
As per NCERT, a few molecules move across the membrane without any requirement of energy, whereas polar molecules cannot pass through the non-polar lipid bilayer; they require a carrier protein of the membrane to facilitate their transport across the membrane.
∴ Substances with a hydrophilic moiety face difficulty in passing through the membrane.
Answer: (3)