Question

Which part of the membrane is responsible for the relative impermeability of polar molecules in and out of the cell?

(a) Polar head

(b) Hydrophobic head

(c) Hydrophobic core

(d) Non polar head

This question was posed to me in a job interview.

Origin of the question is Gastrointestinal Absorption of Drugs in portion Absorption of Drugs of Drug Biotechnology

Answer 1

Correct answer is (c) Hydrophobic core

Easiest explanation: Hydrophobic core don’t bind to any polar compound being hydrophobic, thus it doesn’t allow polar compounds to pass through the membranes easily. Heads of phospholipid bi-layer in cell membrane are always polar and tails are non-polar in nature.