1. Section 3.4 DIFFUSION AND OSMOSIS

2. I. Diffusion and osmosis are types of passive transport A. Passive Transport  the movement of molecules across a cell membrane from high to low concentration without using energy 1. There are 2 types of passive transport:  Diffusion  Osmosis

3.  Diffusion  the movement of molecules from high to low concentration  Goal: Equal concentration in all areas Simple Diffusion AnimationSimple Diffusion Animation Play animation

4.  Osmosis  Diffusion of wate r molecules across a semi permeable membrane from high to low concentration.  Goal: equal concentration of water in all areas

5. Osmosis Osmosis animation Osmosis Water moves freely through pores. Solute (green) too large to move across.

6. 2. Concentration gradient  Difference in concentration of a substance from 1 location to another

7. iso = equal a. Isotonic: the cell and the solution it is in have the same concentration of dissolved particles (solute). The cell stays the same size. 3. Which way water moves depends on the solution the cell is in:

8. shrinks hyper = high a. Animal cell shrinks (salting a slug) b. Causes wilting in plants (plasmolysis) b. Hypertonic: the solution has a higher concentration of dissolved particles(solute) than the cell. The cell shrinks (water leaves the cell and enters the solution).

9. a. Animal cell swells and may bursts open ( cytolysis )! b. Plant cell has cell wall; becomes firmer hypo = low c. Hypotonic: the solution has a lower concentration of dissolved particles than the cell. The cell swells (water leaves the solution and enters the cell).

10. HYPO = HIPPO In a hypotonic solution, cell gains water and swells up  gets big like a hippo

11. What type of solution are the cells in?

12. Hypotonic Hypertonic Isotonic

13. III. Some molecules move across the cell membrane with the help of transport proteins.  Facilitated Diffusion  the diffusion of molecules across a membrane through transport proteins.  The proteins make it easier for larger molecules to move across the membrane.