1. 3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes because of concentration differences.

2. 3.4 Diffusion and Osmosis
Passive transport does not require energy input from a cell.
Molecules can move across the cell membrane through passive transport.
There are two types of passive transport.
diffusion
osmosis

3. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Molecules diffuse down a concentration gradient.

4. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Osmosis is the diffusion of water molecules across a semipermeable membrane.

5. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
There are three types of solutions.
isotonic
hypertonic
hypotonic

6. 3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport proteins.
Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins.

7. If And 3.4 Diffusion and Osmosis
molecules and ions are always jiggling and this internal movement causes them to randomly collide with one another millions of times each second.
And
the rebounds from the collisions propel them through a liquid or gas with the result of being a gradual and complete mixing.

8. What factors can affect the speed at which this diffusion occurs?
3.4 Diffusion and Osmosis
THEN
What factors can affect the speed at which this diffusion occurs?

9. Factors that affect diffusion speed
3.4 Diffusion and Osmosis
Factors that affect diffusion speed
1. Size
It takes more energy to move a large than a small one.

10. Factors that affect diffusion speed
3.4 Diffusion and Osmosis
Factors that affect diffusion speed
2. Concentration
Molecules move faster at higher temperatures.

11. Factors that affect diffusion speed:
3.4 Diffusion and Osmosis
Factors that affect diffusion speed:
3. Temperature
Solutes tend to dissolve “down” a concentration gradient.

12. Factors that affect diffusion speed
3.4 Diffusion and Osmosis
Factors that affect diffusion speed
4. Charge
Each ion or charged molecule contributes to the overall electrical charge of the solution + to –

13. Factors that affect diffusion speed
3.4 Diffusion and Osmosis
Factors that affect diffusion speed
5. Pressure.
It squeezes molecules together; the more crowded they are, the more they rebound.

14. 3.4 Osmosis

15. Diffusion across a cell membrane LAB
INTRODUCTION