Question

a scientist observes that certain molecules can pass through the cell membrane easily, while others cannot. which property of the lipid bilayer is most responsible for this selective permeability?

a. the presence of carbohydrate chains.

b. the hydrophobic interior of the lipid bilayer.

c. the rigid structure of the cell wall.

d. the presence of nucleic acids..

Explanation:

• Option A: Carbohydrate chains on the cell membrane are mainly for cell recognition, not for controlling molecule passage through the lipid bilayer's permeability. So A is incorrect.
• Option B: The lipid bilayer has a hydrophobic (water - fearing) interior. Molecules that are non - polar or small can pass through this hydrophobic region more easily, while polar or large molecules have difficulty. This hydrophobic interior is the main factor for the selective permeability of the lipid bilayer. So B is correct.
• Option C: The cell wall (in plants, fungi, etc.) is a rigid structure outside the cell membrane, and it is not part of the lipid bilayer. The lipid bilayer is part of the cell membrane, so the cell wall's structure has nothing to do with the lipid bilayer's permeability. So C is incorrect.
• Option D: Nucleic acids (DNA, RNA) are inside the cell (in the nucleus or cytoplasm) and are not part of the lipid bilayer. So they can't be responsible for the lipid bilayer's permeability. So D is incorrect.

Answer:

B. The hydrophobic interior of the lipid bilayer.