Osmosis

1. Osmosis Objectives • Describe osmosis as passive transport. • Define isotonic, hypertonic and hypotonic. • Describe what happens to an animal and plant cell in isotonic, hypertonic and hypotonic solutions. Textbook pages 185-186

2. Think! Think!! Think!!! A Google search for “water drinking deaths” returns over 18 million results! This is a common story in the news. How can someone die from drinking too much water?

3. Diffusion

4. Osmosis • Osmosis – the diffusion of water through a selectively permeable membrane from an area of high concentration to an area of low concentration • Osmosis only happens when the membrane is NOT permeable to a solute, but is permeable to water. !!!!!!!!

5. Osmosis – pg 185 • Membrane is permeable to water but not to sugar • More sugar on the left than on the right. Less water on the left than on the right. • Over time, the water passes through the membrane from where there was more to where there was less. The water level changes.

6. Osmosis • Concentration – the amount of dissolved substance in a volume of water • Hypertonic –“above strength” left side of the membrane where solute is more concentrated !!!!! • Hypotonic –“below strength” right side of the solution where solute is less concentrated !!!!!! • Isotonic –“same strength” the second beaker where both sides are equally concentrated !!!!!!

7. Osmosis • Osmosis is passive transport, like diffusion, because it occurs spontaneously without requiring energy. !!!!!

8. Osmosis • Animation

9. How Osmosis Works in Cells • http://www.phschool.com/atschool/phbio/active_art/osmosis/index.html

10. How Osmosis Works on Animal Cells • Page 186 • animation • http://www.linkpublishing.com/video-transport.htm#OSMOSIS

11. How Osmosis Works on Plant Cells • http://www.linkpublishing.com/video-transport.htm#OSMOSIS

12. Drinking Water Deaths • When you drink too much water, are your cells being placed in a hypotonic, hypertonic or isotonic solution? • Will your cells, shrink, burst or stay the same?