1. Semi-permeable Membrane
Only allows certain molecules to pass through
Smaller polar molecules pass easily
Large molecules or nonpolar molecules do not pass through

2. The Structure of the Cell Membrane
Outside
of cell
Inside
of cell
(cytoplasm)

3. Passive CellularTransport:
No energy Required!

4. Passive transport: when a cell moves molecules from high to low concentration
A. No energy required

5. A. Diffusion
1. Net movement of molecules from high concentration to low concentration, down their concentration gradient
Ex. Perfume molecules spreading out in a room

6. H H O H H H O O O H H H O H H O H H O H H O O H H H H H H O O H O H H H H H O O H H O H H O H H

7. Sugar Molecules H H H H O O O H O H H O H O H H H H H O H O O H H H O

8. Sugar Molecules H H H H H O O O O H H O H H H H O O O H H H H O H H H

9. Sugar Molecules H H O H H H O O O H H H H H O O O H H O O H H H H H H

10. Sugar Molecules H H H H O O O H H H O H H O H H H O O O H H H H H O O

11. b. Diffusion never stops!
a. Diffusion rate depends on size of molecules, concentrations and temperature
b. Diffusion never stops!
Molecules just move back and forth slowly even when they are at equilibrium
c. Diffusion requires no energy!

12. B. Osmosis

13. 1. Net movement of water molecules across a semi-permeable membrane, from a high concentration to a low concentration of water
2. No energy is needed
ex. Elodea Plasmolysis

15. Osmosis Cell membrane Water molecules Higher Concentration of Water
Lower Concentration
of Water
Sugar molecules

16. 3. Which way will water flow?
a. Hypotonic Solution: when there is less solute (stuff) outside than inside the cell – Water moves into the cell
Uh...Oh!
SPLAT

17. b. Hypertonic Solution: when there is more solute outside than inside the cell - Water moves out of the cell
Solutes
Cell shrinks

18. c. Isotonic: the concentrations inside and outside the cell are the same (equilibrium)
- Water moves in and out of the cell at the same rate

20. Solutes
Cell shrinks

22. AAARRGHH!
Uh...Oh!
SPLAT

23. Osmosis & Diffusion ?’s
What do we call the process when a sugar cube dissolves in a cup of water?
Osmosis is a type of diffusion. However, what is being diffused in osmosis?
Draw a picture showing what would happen to a raisin put in a cup of water overnight?

24. III. Facilitated Diffusion: molecules are moved across the membrane by carrier proteins
A. Still moving from high to low concentration
No Energy Needed!

25. B. Why would a molecule need a carrier protein?
1. too big to fit through pores, not soluble in lipids (glucose)
C. Carrier proteins have specific shapes for specific molecules (Lock and Key)

26. IV. Diffusion through ion channels: help ions move across membrane
A. Specific for each ion
Ions

27. Active Cellular Transport
Energy Required!
ATP

28. I. Active Transport: when a cell uses energy (ATP) to move molecules up their concentration gradient

29. Cell Membrane Pumps: carrier proteins that “pump” materials up their concentration gradient
1. Revolving Door: as some come in some come out
Requires energy

30. Endocytosis and Exocytosis
1. Used when materials are too large or when lots of stuff is moved into or out of the cell
2. Energy is required!

31. a. Endocytosis: when cells take in stuff from the outside
b. Exocytosis: when a cell releases contents outside the cell ? ?