![Molecular view of diffusion](/exchange/files/imagecache/featured_450px/diffusion2.jpg)
This activity includes two hands-on experiments and numerous analysis and discussion questions to help students understand how the characteristics and organization of the molecules in the cell membrane result in the selective permeability of the cell membrane.
In the hands-on experiments, students first evaluate the selective permeability of a synthetic membrane and then observe how a layer of oil can be a barrier to diffusion of an aqueous solution.
Students answer analysis and discussion questions to learn how the phospholipid bilayer and membrane proteins play key roles in the cell membrane function of regulating what gets into and out of the cell. Topics covered include ions, polar and nonpolar molecules; simple diffusion through the phospholipid bilayer; facilitated diffusion through membrane proteins; and active transport by membrane proteins.
An optional additional page introduces exocytosis and endocytosis.