Facilitated diffusion

Question 1

What is facilitated diffusion

Answer 1

The passive transfer of molecules or ions down a concentration gradient, accross a membrane, by channel and/or carrier proteins

Question 2

Why is facilitated diffusion important

Answer 2

• Some charged ions are unable to easily pass through the non polar centre of the phosphlipid bi layer
  
  • e.g. NA⁺, K⁺, CA²⁺ and Cl⁺
• SImilarly larger polar molecules such as sugar and amino acids are unable to pass through the membrance
• Facilitated diffusion helps this to happen

Question 3

What is the role of channel proteins in facilitated diffusion

Answer 3

• Each channel protein is specific to one ion, e.g. NA⁺ and opens a pore in the cell membrane to allow it to ferry through
• It does not allow other ions through the pore e.g. K⁺
• A channel protein can also decide whether the cell needs that ion (opens the gate) or does not need that ion (closes the gate)

Question 4

What is the role of carrier proteins in facilitated diffusion

Answer 4

• Carrier proteins enable the facilitated diffusion of larger polar molecules such as sugars and amino acids
• A molecule, binds to the carrier protein, changing its shape, as its shape changes the molecule is transfered through the cell membrane

Question 5

Does facilitated diffusion require energy e.g. ATP

Answer 5

• No
• It is a passive process accross a concentration gradient