1. 3.4 Diffusion and Osmosis MA 2.1 Explain the role of cell membranes as a highly selective barrier (diffusion, osmosis, facilitated diffusion, active transport).

2. *two page notebook format* Do Now: 1) What happens to the skin of your fingers and toes if you stay in a hot bathtub for too long? Why does that happen? 2) What happens if you dump Kool-Aid mix into a glass of water, but you do NOT stir it up? Wednesday, Sept 30, 2015 Topic: Diffusion and Osmosis Objectives: Describe passive transport Distinguish between osmosis, diffusion, and facilitated transport Agenda Homework check 3.3 Exploration: Kool-Aid Exploration: salt, water, and raisins Notes & problems 3.4 Page 26Page 27

3. What happens to the skin of your fingers and toes if you stay in a hot bathtub for too long? Why does that happen?

4. What happens if you dump Kool-Aid mix into a glass of water, but you do NOT stir it up?

5. Exploration: Kool- Aid Predict: What will happen when you dump Kool-Aid into a glass but do NOT stir it up? Try it! Wait 15 minutes and see what happens. Record results: Sketch a picture of what you see. Explain: Why did that happen?

6. Exploration: Raisin in salty or plain water Predict: What will happen if you put a raisin into plain water? What if you put a raisin into salty water? Try it! Wait at least 30 minutes to see what happens. Record results: Sketch a picture of what you see. Explain: Why did that happen?

7. Diffusion and Osmosis are types of passive transport Diffusion  The movement of molecules in a liquid or gas.  Molecules move from area of HIGH concentration to LOW concentration.  Concentration gradient is the difference in concentration between two areas.  No energy is required from the cell to make this happen. Osmosis  A special case of diffusion, only for water.  Water also spreads out, or moves from HIGH to LOW concentration.  If a lot of things are dissolved in water, that means the concentration of water is lower, so fresh water will move in to dilute the solution.

8.  Isotonic = equal concentration of water inside and outside the cell. No water movement.  Hypertonic = the solution has a HIGER concentration of dissolved particles than the cell. Water will leave the cell.  Hypotonic = the solution has a LOWER concentration of dissolved particles than the cell. Water will enter the cell. Three definitions for Osmosis or Water concentration

9.  Facile = easy. Facilitated = made easier.  Some molecules diffuse through transport proteins or protein channels.  If a molecule crosses the cell membrane through a protein channel, it is easier to cross, so we call it facilitated diffusion. Facilitated diffusion

10.  Complete Section 3.4 in your student book.  Complete selected sections on the back of the Cell Organelles graphic organizer. Classwork and homework