Question

How does facilitated diffusion differ from diffusion?

Answer 1

Diffusion-

The movement of molecules along the concentration gradient is called simple diffusion.

Facilitated diffusion-

The movement of molecules through a membrane along the concentration gradient with the help of carrier molecules is called facilitated diffusion.

Diffusion	Facilitated diffusion
1 Unassisted movement of molecules from a higher to a lower concentration.	1 Transport of molecules across a biological membrane along the concentration gradient by a carrier molecule.
2. Occurs through the phospholipid bilayer.	2. Occurs through transmembrane proteins.
3. Rate of diffusion is directly proportional to the concentration gradient.	3. Rate of diffusion depends on the kinetics of carrier-mediated transport.
4. Transports small, non-polar molecules.	4. Transports large, polar molecules.
5. Example- diffusion of respiratory gases across the respiratory membrane.	5. Example- Cotransport of sodium with glucose.