Cells (transport across membranes) - co-transport + facilitated diffusion

Question 1

What is the difference between diffusion and facilitated diffusion through a cell membrane?

Answer 1

• Facilitated diffusion relies on kinetic energy of molecules
• Facilitated has to happen through transmembrane channels and carriers

Question 2

What is the function of protein channels in facilitated diffusion?

Answer 2

• Water filled hydrophilic channels
• Allows specific water soluble ions to pass through
• Remains closed unless specific ions are present

Question 3

What is the function of carrier proteins in facilitated diffusion?

Answer 3

• Molecule has to be specific to the protein
• Molecule binds to protein which causes it to change shape and then is released
• Only uses kinetic energy of molecules

Question 4

Describe co-transport

Answer 4

• Carrier proteins can sometimes transport two particles at once
• Both must be present for active transport to take place
• Often both an active + passive process as one particle is moved out against it
• Substances can be moved in the same (symport) or opposite (antiport) directions