Describe the factors that will affect the ability of a molecule to diffuse throu

The first factor that will affect the permeability of a membrane to simple diffusion is the lipid solubility of the molecule. The more lipid soluble a molecule is, the greater the chance that molecules will be able to diffuse directly across the lipid bilayer. At the same time, the lipid composition of the membrane will affect the permeability of lipid soluble molecules through the membrane. Second, the size and shape of a molecule will affect its permeability. As a molecule gets larger and more irregular in shape, it will move through the membrane more slowly, thereby reducing its permeability.

Temperature will also have a substantial effect on how quickly a molecule can move across the membrane. The higher the temperature, the greater that molecule's membrane permeability. However, within the body, temperature tends to change little, which means that temperature should only have a small affect on membrane permeability. Finally, the thickness of the layer of cells that must be crossed will also affect diffusion. The further a molecule has to move, the longer it will take to get there, thereby reducing that molecule's permeability.