TRANSPORT – Facilitated Diffusion
Facilitated diffusion – PASSIVE net movement of molecules/ions from a region of high to low conc. but through a CARRIER/channel protein across the membrane
Process:
- Hydrophilic molecules/ions can’t move through the hydrophobic (centre) barrier
- Channel proteins allow specific ions (Na+, or K+, or Ca2+ or Cl-) to pass through them.
- Channel proteins form a pore that a specific ion can just pass through very rapidly.
- Carrier proteins usually move molecules through them. (e.g. AA’s/sugars)
- Carrier proteins bind the molecule to the protein on one side of the membrane, change shape, and release it on the other side
