What determine the movement of water insoluble substance in the body:

The lipids in cell membrane provide a barrier to movement of water & water-soluble substances. Lipid solubility is the chief factor determining the movement of water insoluble substances. Fat soluble substances such as O2, CO2 and alcohol can penetrate the membranes with ease. E.g.: CO2 is 20 times more lipid soluble than O2 hence diffuses across membranes much faster. Factors influencing movement of water-soluble substances: Charge Molecular wt. Hydrated diameter of molecule. Presence of channels, pores, carriers, pumps.