How is facilitated diffusion different than simple diffusion?

Question

Facilitated diffusion uses proteins in the membrane to help move molecules down the concentration gradient.
Facilitated diffusion does NOT use proteins to move molecules.
Facilitated diffusion uses energy and simple diffusion does not.

Answer 1

The correct distinction is:

Facilitated diffusion uses proteins in the membrane to help move molecules down the concentration gradient.

In facilitated diffusion, specific transport proteins assist in moving substances across the cell membrane, typically when those substances are too large or polar to pass through the lipid bilayer freely. This process does not require energy (it is passive) and occurs down the concentration gradient.

In contrast, simple diffusion occurs directly through the lipid bilayer and does not involve any transport proteins. Like facilitated diffusion, simple diffusion is also a passive process that moves molecules down their concentration gradient.

So the main difference is that facilitated diffusion requires specific proteins to aid the movement of certain molecules, while simple diffusion does not.