Facilitated Diffusion (College Board AP® Biology) : Study Guide
Facilitated diffusion
The structure of a molecule affects its ability to pass through the plasma membrane
Specialized membrane proteins are required to allow the passive transport of large, polar molecules and ions across the bilayer; this is facilitated diffusion
These proteins are highly specific, allowing the transport of only one type of substance
The transport proteins that allow facilitated diffusion can either be:
channel proteins: pores that allow the passage of substances
carrier proteins: proteins with a binding site on one side of a membrane that change shape to release the transported substance on the other side
Examples of facilitated diffusion include:
passage of water via transport proteins known as aquaporins
transport of ions, including Na+ and K+
Examiner Tips and Tricks
Be careful not to confuse facilitated diffusion with active transport. Both processes can involve carrier proteins, but facilitated diffusion involves movement down a concentration gradient, and so does not require an energy input, while active transport involves movement against a gradient, and so requires energy from ATP
You've read 0 of your 5 free study guides this week
Sign up now. It’s free!
Did this page help you?
