Explain why ions do not move through ion channels by only simple diffusion, whereas water does move through water channels by simple diffusion.
specifically, what, in addition to the concentration gradient, affects the movement of ions through ion channels?

Electrical gradient.

Explanation:

Ions DO NOT move in Ion channels by simple diffusion because most ion channels can be:

I) selective of ions pass through it.

II) operating on a "open and close" principle. Where it opens or close on its own accord OR does so ONLY when induced by a specific influence like change in voltage of ion channels.

IN ADDITION to the concentration gradient, ELECTRICAL GRADIENTS (change in membrane voltage) affects the movement of ions through ion channels

cuz they cant breath

explanation:

condensation. good luck!