1. Diffusion The movement of molecules from an area of high concentration to an area of low. concentration.

2. Diffusion causes many substances to move across cell membranes. No energy is require of the cell.

3. Osmosis Osmosis is the diffusion of water through a selectively permeable membrane

4. Hypertonic solution p. 186 - 187  contains a higher concentration of impermeable solutes outside of the cell.  Water will flow out of the cell  The cell will shrink

5. Hypotonic solution  contains a lower concentration of impermeable solutes outside of the cell.  Water will flow into the cell  The cell will swell

6. Isotonic solution  The concentration of impermeable solutes is the same inside and outside the cell.  Water will flow in and out of the cell at an equal rate.  The cell will not change size.