Diffusion & Osmosis

1. Diffusion & Osmosis

2. Schema Activator • Evaluate the following claims: • 9 out of 10 people surveyed say that the bag lunches at GPA are among the best they’ve ever had • 100% of people surveyed say that cell phones and music players should not be allowed in schools • What questions come to mind when you read these statements?

3. Movement of Materials • We have looked at cells and the structures that help make and transport materials throughout the cell • How do the materials enter and leave the cell? • Cell membrane- selectively permeable…write what you think this means in your science notebooks

4. Define selectively permeable membrane • A membrane that allows only certain materials to cross it • Materials pass through pores in the membrane

5. Structure of Cell Membrane • The cell membrane has a unique structure that controls how things enter and leave the cell, referred to as the fluid mosaic model • Lipid bilayer • Hydrophilic heads • Hydrophobic tails • Carrier proteins

6. How Materials Move • Materials move through the cell membrane through a process called Diffusion • Write down what you think diffusion is in your science notebook. • http://www.brainpop.com/science/matterandchemistry/diffusion/

7. Define Diffusion The movement of molecules from a area in which they are highly concentrated to a area in which they are less concentrated.

8. Draw a diagram of an example of diffusion we saw in class.

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

10. Define osmosis

11. Define osmosis • The diffusion of water across a selectively permeable membrane.

12. Define 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). http://www.usd.edu/~bgoodman/Osmos.htm

13. Define osmosis http://www.usd.edu/~bgoodman/Osmos.htm

14. Define osmosis • 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. http://www.usd.edu/~bgoodman/Osmos.htm

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

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

17. Types of Passive Transport • Diffusion • Osmosis • Facilitated Diffusion • Carrier Proteins • Ion channels • Some always open • Some gated • http://www.brainpop.com/science/cellularlifeandgenetics/passivetransport/

18. 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

19. Active Transport • If passive transport is the movement of materials from an area of greater to lesser concentration, what do you suppose active transport is? Write your answer in your science notebook Types of Active Transport: • Cell Membrane Pumps • Endocytosis • Exocytosis • http://www.brainpop.com/science/cellularlifeandgenetics/activetransport/

20. Endocytosis & Exocytosis

21. Review Osmosis & Diffusion Here: http://wappingersschools.org/WJH/teachers/science/Jim_Site/asignments/cells/diffusionetc/diffusion_osmosis.html

22. Homework • Read pp. 95-100 • Do questions 1-6 on pg. 100 • Read pp. 100-104 • Do questions 1-6 on pg. 104