1. Guiding Question: What is the importance of the membrane?

2. Vocabulary of Solutions  Solute- the substance dissolved in a solution  Solvent- the substance in which a solute is dissolved  Examples- In a solution of salt dissolved in water: In a solution of salt dissolved in water: * Salt is the solute; water is the solvent What about starch and iodine? What about starch and iodine?

3. Osmosis  Osmosis - the diffusion of water across a semi permeable membrane towards the side with higher solute concentration.  The membrane is not a barrier to water so it moves to equalize the solute concentrations either side of the membrane.  Because the membrane is impermeable to most solutes so the solute cannot diffuse to help out with equilibrium.  So when solutes are concentrated inside or outside the cell, it will draw the water in its direction. REMEMBER REMEMBER..

4. Vocabulary of Osmosis  NB: OSMOSIS VOCABULARY REFERS TO THE CONCENTRATION OF THE SOLUTE  hypertonic solution- a solution with a higher solute concentration than what it is compared with. [Hyper = More than] [Hyper = More than]  hypotonic solution- a solution with a lower solute concentration than what it is compared with. [Hypo = Less than] [Hypo = Less than]  isotonic solution a solution with an equal solute concentration to what it is compared with. [Iso = The same as] [Iso = The same as]

5. Visual examples Solution is hypotonic to cell. Cell is hypertonic to solution. Solution is hypertonic to cell. Cell is hypotonic to solution. Solution is isotonic to cell. Cell is isotonic to solution.

6. Osmosis and Red blood cells

7. Sugar syrup Egg whites Water More concentrated solution OUTSIDE cell Less concentrated solution inside cell More concentrated solution INSIDE cell Less concentrated solution outside cell Same concentration inside and outside of cell (CONTROL)

8. Osmosis Happens!  Living things invest a great deal of effort [Energy] [?] to counteract Osmosis.  Cells use energy to maintain the balanced equilibrium of the cell [homeostasis] by actively moving molecules across cell membranes thus avoiding cells “drying out” or “exploding”.  Osmosis is why: you get thirsty after eating something really salty or sweet. you get thirsty after eating something really salty or sweet. why you cant drink seawater when shipwrecked. why you cant drink seawater when shipwrecked. why you need to drink water after sweating a lot. why you need to drink water after sweating a lot.

9. Using the new vocabulary 1. Does the water move by osmosis towards the hypertonic or hypotonic side of a semipermeable membrane? 2. In a short sentence explain why osmosis occurs. 3. If a cell is placed in hypertonic solution, will it shrink, swell, or stay the same size? 4. If a cell is placed in isotonic solution, will it shrink, swell, or stay the same size?