4. Let’s look at one example involving osmosis. Osmosis is the diffusion of water across a semi permeable membrane such as a cell membrane. A semi permeable membrane is one that only certain types of molecules can cross. For example, water can cross a cell membrane, but many other substances can’t.

5. 5 Simple Diffusion NO Requires NO energy HIGH to LOW Molecules move from area of HIGH to LOW concentration

7. 7 DIFFUSION

9. active transport moves particles against the concentration gradient— from an area of low concentration to an area of higher concentration

11. PHOSPOLIPID