MEMBRANE PERMEABILITY BIOLOGY AL Teaching Notes MEMBRANE PERMEABILITY

Topics Include Structure of membranes Factors affecting membrane permeability

Structure of Membranes

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

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

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

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

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

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