Facilitated diffusion

• What is facilitated diffusion?

  The transport of substances across a membrane from a higher to lower concentration using a transport molecule (e.g. a protein)
• What type of particle can be transported by facilitated diffusion?

  Charged particles, non-polar molecules and large molecules that are too big to cross a membrane by simple diffusion
• What is facilitated diffusion affected by?

  -temperature

  -number of protein carriers

  -concentration gradient
• How does the number of protein carriers affect the rate of facilitated diffusion?

  This limits the rate of diffusion, as a maximum rate means all the proteins are in use.
• How does concentration gradient affect the rate of diffusion?

  As concentration gradient increases, the rate of diffusion increases. If the concentration of molecules outside the cell is very high relative to the internal cell concentration, the rate of diffusion will be very high.