Simple and Facilitated Diffusion

[cricketcrazynerd]

Hey fellow biologists

I was making note for 2.4.5 using Pearson Book and the Oxford study guide and both are giving me contradictory explanations for facilitated diffusion.

Oxford says:

Facilitated diffusion is when for substances to pass between phospholipid molecules, channel proteins are need

Pearson says:

Simple diffusion --> substances other than water move between phospholipid molecules or through proteins which possess channels

Facilitated diffusion --> Non-channel protein carriers change shape to allow movement of substances other than water

Which one is correct or are they both correct and I am just interpreting the language wrong??

I know it's an easy question, but I'm very confused....

Thanks

[Lero]

As far as I know the Oxford study guide explanation is simpler and makes more sense. Simple and facilitated diffusion both are passive and occur down the concentration gradient. Whereas in simple diffusion the molecules are small (and often non-polar) and can pass through the phospholipid bilayer (oxygen gas for example), in facilitated diffusion channel proteins are required which allow larger molecules to diffuse down the concentration gradient such as the action potential part of nerve transmission where sodium ions diffuse into the axon while potassium ions diffuse out of the axon.

Edited February 22, 2013 by Hus

[Guest HayashiEsme]

I believe simple diffusion is the movement of molecules across the membrane; whereas facilitated diffusion is the movement of molecules across a channel protein.

Your interpretation of facilitated diffusion from the Pearson book seems to be the definition for active transport: where a pump is required.

All the best! Biology at IB's an awesome awesome subject to take, but the terms can trip you up sometimes:)