Question

Differentiate between simple diffusion and facilitated diffusion?

Answer 1

Hint: Simple diffusion is the movement of particles takes place along the direction of the concentration gradient. Whereas, in facilitated diffusion, the movement of molecules can occur both ways – along the direction as well as opposite of the concentration gradient.

Complete answer:

Characteristics	Simple Diffusion	Facilitated Diffusion
Definition	Simple diffusion is a type of passive transport. It is simply the unassisted movement of solute, occurs when its electrochemical potentials on the two sides of a permeable barrier varies	Facilitated diffusion is type of operation of biological transport. It is a specific structural component of biological membranes which interact with particular solutes or classes of solutes.
Energy requirement	It is a passive transport and doesn’t require any energy.	It is also a passive transport mechanism that doesn’t require any energy, but some facilitated diffusion processes can be active.
Speed	The speed of simple diffusion is low.	The speed of facilitated diffusion is high.
Inhibition	This is not inhibited by an inhibitor molecule.	This can be inhibited by specific inhibitor molecules.
Direction of movement	In simple diffusion, the movement of particles takes place with the direction of the concentration gradient.	In facilitated diffusion, the movement of molecules can take place in both ways – along the direction and opposite of the concentration gradient.
Size of molecules	Simple diffusion is involved in the passage of small molecules along with non-polar molecules.	Facilitated diffusion is commonly involved in the movement of large as well as polar molecules across a biological membrane.

Note: Movement of metabolites across the membrane along the concentration gradient as well as without the use of a carrier molecule is called simple diffusion. Simple diffusion is relatively a slow process. On the contrary side, facilitated diffusion is a more rapid form, in this process molecules move through channels in the membrane.