Question

The cell membrane forms a protective barrier between the external and internal environments. It is referred to as ___________________, because it allows some substances to cross more easily than others and blocks other substances from crossing into the cell. A) impermeable B) a fluid mosaic C) a plasma membrane D) selectively permeable

Answer 1

D.) Selectively permeable

Answer 2

The right answer is D) selectively permeable.

Biological membranes only let certain molecules or ions pass, and not at the same speed. This selective permeability is the result of differential passive permeability, which more or less limits the crossing of particles driven by osmotic and electrostatic forces, and biological permeability or permeation, which ensures active transport by enzymatic mechanisms.