2.5.2 Membrane Structure & Permeability

Question 1

How does temperature affect membrane permeability?

Answer 1

• High temperatures increase fluidity of lipids
• Reduces effectiveness of cell membrane to act as a barrier to polar molecules
• Any diffusion occurs at a higher speed due to increased kinetic energy
• Very high temps denature proteins in the membrane
• So membrane structure is disrupted and it is no longer an effective barrier

Question 2

How does solvent concentration affect membrane permeability?

Answer 2

• Organic solvents dissolve lipids in membrane
• So higher concentrations increase the permeability of the cell membrane
• Because it loses it structure

Question 3

Channel proteins notes

Answer 3

• Facilitated diffusion
• Large polar molecules and ions (charged molecules)
• Specific
• Gated, so controls exchanges of substances

Question 4

Carrier Protein notes

Answer 4

• Facilitated diffusion
• Switches between 2 shapes
• Causes binding site of carrier protein to be open on one side and closed on the other
• Direction of movement of molecules depends on concentration gradient