Membrane Permeability

Question 1

What is a semi permeable membrane

Answer 1

A layer which only allowed substances can pass

Question 2

What is passive transport dependent on?

Answer 2

Permeability and concentration gradient

Question 3

How can you measure permeability?

Answer 3

Black film

Question 4

What substances can and cannot pass lipid bilayer?

Answer 4

Can pass: 
hydrophobic molecules
O2
CO2
N2
Benzene 
Small uncharged polar molecules (H20, urea, glycerol)

Cannot pass: large uncharged polar molecules (glucose/sucrose) and IONS

Question 5

What scale is used to measure permeability

Answer 5

Logarithmic permeability co-efficient - large differences between molecules

Question 6

What roles do transport processes (proteins) have?

Answer 6

Maintain ionic composition
Intracellular pH regulation
Cell volume regulation
Concentration of metabolic fuels and building blocks
Remove waste products and toxic substances
Generate ion gradients for exciting nerves

Question 7

How are transport proteins modelled

Answer 7

Gated pore and a ping pong like transport
Allows:
Facilitated diffusion
Ion channel (ligand gated/voltage gated)

Question 8

What does membrane transport depend on

Answer 8

Concentration and membrane potential

Question 9

Active transport

Answer 9

Transport of ions or molecules against unfavourable concentration/electrical gradient

Uses ATP hydrolysis indirectly/directly for energy

Question 10

G values of reactions

Answer 10

+ve G value = active process, requires energy

-ve G value = releases energy