Learning Objectives

1. Understand the essential structure and function of the cell membrane.
2. Know the forces that cause water and solutes to move across membranes passively (that is, without expending energy).
3. Understand which types of substances move by simple diffusion and which by bulk flow.
4. Understand the importance of osmosis to all cells.
5. Know the mechanisms by which substances are moved across membranes against a concentration gradient (actively, with energy expenditure).
6. Understand how material can be imported into or exported from a cell by being wrapped in membranes.