Facilitated and simple diffusion difference

Question

What is the basic difference among facilitated and simple diffusion? Facilitated by which kind of molecule does the word “facilitated” mean?

Answer 1

Simple diffusion is a direct passage of substances across the membrane in preference of their concentration gradient. In the facilitated diffusion, movement of substances is as well in favor of their concentration gradient however the substances move bound to particular molecules which act as “permeabilizers”, that is, facilitators of their passage via the membrane.