Question

cell membranes are said to be ______ because they allow some substances to pass but not others.
options:

• doubly amphipathic
• impermeable
• hydrophobic
• hydrophilic
• selectively permeable

Explanation:

To solve this, we analyze each option:

• "doubly amphipathic" refers to molecules (like phospholipids) having both hydrophobic and hydrophilic regions, not membrane permeability to substances.
• "impermeable" means no substances can pass, which contradicts the statement (it allows some).
• "hydrophobic" means repelling water, not about selective substance passage.
• "hydrophilic" means attracting water, also not about selective passage.
• "selectively permeable" means allowing some substances to pass while restricting others, which matches the description of cell membranes.

Answer:

E. selectively permeable