Question

Why do ions have a difficult time getting through plasma membranes despite their small size?

a) Ions are repelled by the lipid bilayer
b) Ions lack electrical charge
c) Ions cannot form hydrogen bonds
d) Ions are water-soluble

Answer 1

d) Ions are water-soluble. The difficulty ions face in traversing plasma membranes is primarily attributed to their hydrophilic (water-attracting) nature. Plasma membranes, composed of a lipid bilayer, create a hydrophobic (water-repelling) barrier.

Step-by-step explanation:

d) Ions are water-soluble. The difficulty ions face in traversing plasma membranes is primarily attributed to their hydrophilic (water-attracting) nature. Plasma membranes, composed of a lipid bilayer, create a hydrophobic (water-repelling) barrier. The lipid tails within the membrane form a nonpolar interior, creating an environment unfavorable for charged, water-soluble ions to pass through easily. The hydrophobic core of the membrane impedes the movement of ions, hindering their diffusion through the lipid bilayer. To facilitate ion transport, cells utilize specialized proteins such as ion channels and transporters embedded in the membrane, providing selective passages for ions to move across the hydrophobic barrier and maintain cellular homeostasis.