What prevents ions from crossing the plasma membrane via

simple diffusion?

A. Ions are too large.

B. Ions carry a charge.

C. Ions are hydrophobic.

D. Ions do not produce a concentration difference.

E. Ions cannot interact with membrane-bound

proteins.

Simple diffusion is the concept of a substance moving from an area of high concentration to a lower concentration without energy input. Because the plasma membrane is made of lipids which are non-polar, this membrane readily allows non-polar substances to diffuse through easily. If a substance has a charge like that of an ion, it will be difficult for the ion to cross the plasma membrane through simple diffusion. The answer should be B.