ividly demonstrate selective permeability using coloured solutions. Starting with a model cell and a mixture of special dye solutions, your students will observe how the cell’s membrane allows one dye to pass, while the other remains within the cell. The resulting colour change provides a vivid demonstration of selective permeability and how the cell absorbs nutrients and discharges wastes. The class will also learn how osmosis and diffusion permit the maintenance of equilibrium through the passive transport of water through the cell’s semipermeable membrane.