Explain what is happening in this clip.

1. Explain what is happening in this clip.

2. Objective: You will be able to explain how molecules move across a semi-permeable membrane due to a concentration gradient.Diffusion & Osmosis

3. Diffusion The movement of molecules from an area in which they are highly concentrated to an area in which they are less concentrated.

4. See an animation of diffusion here: http://lewis.eeb.uconn.edu/lewishome/applets/Diffusion/diffusion.html

5. How did the lab illustrate diffusion? Explain or draw a diagram

6. Osmosis • The diffusion of water across a selectively permeable membrane.

7. Osmosis • Water moves from a high concentration of water (less salt or sugar dissolved in it) to a low concentration of water (more salt or sugar dissolved in it).  This means that water would cross a selectively permeable membrane from a dilute solution (less dissolved in it) to a concentrated solution (more dissolved in it).

8. What happens when the concentration of water differs on both sides of a membrane? http://www.usd.edu/~bgoodman/Osmos.htm

9. See an animation of osmosis here: http://lewis.eeb.uconn.edu/lewishome/applets/Osmosis/osmosis.html

10. Animal cells in WATER • In this picture a red blood cell is put in a glass of distilled water (all water with no salt or sugar in it).  Because there is a higher concentration of water outside the cell, water enters the cell by OSMOSIS.  In this case too much water enters and the cell swells to the point of bursting open.  In the end pieces of cell membrane are left in the water.

11. Isotonic cells Hypertonic cells Hypotonic cells Normal Distilled water Salt water

12. Define selectively permeable membrane

13. Selectively permeable membrane • A membrane that allows only certain materials to cross it • Materials pass through pores in the membrane

14. For more information on diffusion & osmosis, click here: http://edtech.clas.pdx.edu/osmosis_tutorial/default.html

15. Why are osmosis & diffusion important?

16. Why are osmosis & diffusion important? • All living things have certain requirements they must satisfy in order to remain alive – maintain homeostasis • These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. • These tasks happen at the cellular level. • Molecules move through the cell membrane by diffusion

17. Why are osmosis & diffusion important? • All living things have certain requirements they must satisfy in order to remain alive. These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. These tasks ultimately occur at the cellular level, and require that molecules move through the membrane that surrounds the cell.

18. Why are osmosis & diffusion important? • This membrane is a complex structure that is responsible for separating the contents of the cell from its surroundings, for controlling the movement of materials into and out of the cell, and for interacting with the environment surrounding the cell.