1. 3.2 Diffusion and Cell Transport

2. POINT > Describe the cell membrane as selectively permeable
POINT > Define diffusion
POINT > Describe osmosis
POINT > Distinguish between passive and active transport
POINT > Identify types of active transport

3. POINT > Describe the cell membrane as selectively permeable
ALL cells have a cell membrane made of lipids, with some proteins and carbohydrates

4. SOME cells have cell walls – ex: plants, fungi and bacteria
POINT > Describe the cell membrane as selectively permeable
SOME cells have cell walls – ex: plants, fungi and bacteria

5. Plant cells have a cell wall made of cellulose, a carbohydrate
POINT > Describe the cell membrane as selectively permeable
Plant cells have a cell wall made of cellulose, a carbohydrate
Bacteria and fungi also have cell walls, but they do not contain cellulose
Cell walls are porous. Water, carbon dioxide, oxygen and nutrients pass through easily

6. POINT > Describe the cell membrane as selectively permeable
The cell membrane separates the inside of a cell from the outside environment
The cell membrane is the “Gatekeeper” of the cell. It controls the movement of materials into and out of the cell

7. POINT > Describe the cell membrane as selectively permeable
The cell membrane is selectively permeable: it allows some substances to pass through and stops other substances

8. CHECK:
What is the cell membrane made of?
What is the plant cell wall made of?
What does selectively permeable mean?

9. Diffusion does not require energy from the cell, it is passive
POINT > Define diffusion
Diffusion is the movement of particles from an area of high concentration to an area of low concentration
Diffusion does not require energy from the cell, it is passive
Passive means no energy is required
outside of cell
inside of cell

10. POINT > Define diffusion
Particles move from high concentration to low concentration during diffusion

11. POINT > Define diffusion
Diffusion is an important way that small molecules can enter cells
Ex. Oxygen moves into cells and carbon dioxide moves out of cells by diffusion (ex.in the lungs)
Unicellular organisms also use diffusion to get gases and other nutrients from the environment

12. POINT > Define diffusion

13. POINT > Define diffusion

14. POINT > Define diffusion

15. CHECK:
What does “passive” mean?
Does diffusion require energy from the cell?

16. POINT > Describe osmosis
Osmosis is the diffusion of water through a selectively permeable membrane (like the cell membrane)
Water diffuses across a membrane from an area of high concentration to an area of low concentration

17. POINT > Describe osmosis
Osmosis can be a problem if the cell gains or loses too much water
Blood must be isotonic with the cell!

18. POINT > Describe osmosis
Cell in Blood
Cell in pure water
Cell in very salty water

19. CHECK:
What is osmosis?
During osmosis, water
a) does not move
b) goes from low concentration to high concentration
c) goes from high concentration to low concentration
What happens to a cell placed in pure water?
What happens to a cell placed in very salty water?

20. Larger molecules cannot diffuse through the membrane
POINT > Distinguish between passive and active transport
Larger molecules cannot diffuse through the membrane
Protein channels and carrier proteins help larger molecules like glucose diffuse across. This is also passive transport

21. CHECK:
How does a larger molecule like glucose get across the cell membrane?
Does the diffusion of glucose into the cell by a carrier protein require energy?

22. POINT > Identify types of active transport
Active transport is the movement of molecules from areas of low concentration to areas of high concentration
Energy is required because molecules must be moved against the concentration gradient

23. POINT > Identify types of active transport
Here a transport protein uses energy to move a sugar against its concentration gradient

24. CHECK:
Does active transport require energy?
Active transport requires energy because
a) movement is with the concentration gradient
b) movement is against the concentration gradient

25. White Blood Cells engulf bacteria, this also requires energy
POINT > Identify types of active transport
White Blood Cells engulf bacteria, this also requires energy
Some unicellular organisms feed by engulfing

27. CHECK:
Tell whether it is passive transport or active transport:
1) osmosis
2) diffusion
3) engulfing

28. Homework:
Read pages 80-85
S.A. page 85 #1-3
GRAS pages 42-43