1. MEMBRANE PERMEABILITY
BIOLOGY
AL Teaching Notes
MEMBRANE PERMEABILITY

2. Topics Include Structure of membranes
Factors affecting membrane permeability

3. Structure of Membranes

4. Fluid mosaic Model cell membrane consists of a lipid bilayer
globular proteins appear in the layer in a mosaic pattern
polar groups of lipid and protein molecules are in contact with water
non polar groups are embedded in the interior of the membrane

5. Fluid mosaic Model
some proteins are localized and some are capable of lateral movement, making the cell membrane a dynamic, ever changing structure
different membrane are different in their composition, arrangement and location of proteins

6. Fluid mosaic Model Polar head Non polar tail
Diagram showing the structure of Lipid Bilayer

7. Factors affecting Membrane Permeability
charged and polar molecules: diffuse slowly through the membrane as they are repelled by the non polar lipids of the membrane
uncharged and fat-soluble molecules: pass through membrane much quickly

8. Factors affecting Membrane Permeability
size of particles increases: permeability decreases
solubility in fat increases: permeability increases
temperature increases: permeability increases but too high temperature can denature and destroy the membrane

9. Factors affecting Membrane Permeability
extreme pH: denature protein and destroy the membrane
presence of narcotics: cause the destruction of membrane by dissolving the lipids on it