Facilitated diffusion

• Facilitated Diffusion


  Type of passive transport where a protein (carrier) helps facilitate the movement of molecules across the cell membrane, no energy input required
• Carrier Protein's Role


  Binds to the molecule, undergoes conformational change, facilitates movement of molecule through the membrane
• Molecules that Bind


  Sugars, Amino Acids, Hormones, Nutrients
• What is facilitated diffusion

  Polar molecules such as water, glucose and ions such as Na+ and cl- cannot pass through the cell membrane.

  so they rely on facilitated diffusion.
• What two protein molecule involved in FD

  1. Carrier protein
  2. channel protein
• Carrier protein

  1. Have binding site for a specific chemical
  2. when a chemical binds it causes the tertiary structure of the carrier protein to change
  3. the carrier protein changes shape, which transfers the substances to the other side of the membrane
• Channel protein

  1. is a protein with a central pore or channel is lined with hydrophilic amino acids and contains water
  2. hydrophilic substances can pass through to the cell membrane to the other
  3. are SELECTIVE for the chemical that can pass through - meaning only certain chemicals can pass through each type of protein
• Carrier protein larger or smaller

  Are for larger molecules such as glucose or amino acid
• Channel protein size 


  Are for smaller molecules such as ion molecules.