Permeability of membrane high permeability to molecules that are gases e.g. O2, CO2 lipid soluble e. g. ethanol non-polar e.g. urea low permeability to ions e.g. K+, NO3- very low permeability to divalent ions e. g Mg2+, SO42Permeability of membrane • high permeability to molecules that are: gases e.g. O2 ,CO2 • lipid soluble e.g. ethanol • non-polar e.g. urea • low permeability to ions e.g. K+ , NO3 - • very low permeability to divalent ions e.g. Mg2+, SO4 2-