1. Westside High School 9th Grade Biology
Crossing the Plasma Membrane

2. Questions What is the job of the plasma membrane?
What is semi-permeable?
What is the difference between active transport and passive transport?
What is osmosis?
What will happen to a cell when placed in a hypertonic solution? Hypotonic solution?
What are examples of each type of transport?

3. It controls what goes into and out of the cell
The plasma membrane maintains homeostasis for the cell It is selectively permeable:
It controls what goes into and out of the cell

4. Plasma Membrane Structure
Two key components of the membrane:
Phospholipids – form the membrane
Proteins – act as “gates”

5. Two forms of transport across the membrane:
Active Transport
ENERGY used
Examples:
Endocytosis
Exocytosis
Passive Transport
No energy needed
Examples:
Diffusion
Osmosis

6. Two forms of transport:
Passive Transport
Diffusion Osmosis
* Does not use energy
Active Transport
Endocytosis Exocytosis
* Uses energy

7. Active transport
Endocytosis
Figure 3.8

8. Active transport
Exocytosis
Figure 3.8

9. Active Transport Endocytosis Exocytosis
Pino-
Phago-
Exocytosis
Ion pumps: Thru a protein, but using energy
Figure 3.9

10. Active Transport: Energy Used? Examples?

11. Passive Transport: Diffusion
Small, uncharged particles are able to pass right between the phospholipids
This is called simple diffusion

12. Passive Transport: Diffusion
There are also proteins embedded between the phospholipids.
These proteins function as gates, allowing larger or charged molecules to get in/out of the cell
Only molecules which are “recognized” are allowed thru these proteins
This is facilitated diffusion

13. Passive transport: Diffusion
Concentration gradient:
Higher Concentration
Lower Concentration
Molecules collide – pass thru membrane

14. Osmosis is the movement of water
Water moves TOWARDS the molecules
Think of it as “water wants to dissolve stuff”

15. Passive Transport: Osmosis
HYPERtonic ISOtonic HYPOtonic
Which way will water move in each case?

16. Passive Transport: Osmosis
HYPERtonic ISOtonic HYPOtonic

17. What do plant cells have outside of the cell membrane that animal cells do not have? What difference will this make with osmosis?

18. Effect of osmosis on plant cells
Flaccid -
Turgid
due to plasmolysis
- cell shrinks from cell wall

19. Passive transport: osmosis
Which way will water move?

20. Passive Transport Energy? Examples?

21. Hypertonic or Hypotonic?

22. Crossing the Plasma Membrane
Passive Transport
Active Transport

23. Crossing the Plasma Membrane
Passive Transport
No energy needed
Diffusion
Osmosis
Active Transport
ENERGY used
Endocytosis
Exocytosis

24. Post test What is the job of the plasma membrane?
What is semi-permeable?
What is the difference between active transport and passive transport?
What is osmosis?
What will happen to a cell when placed in a hypertonic solution? Hypotonic solution?
What are examples of each type of transport?