1. Transport Across Cell Membranes pg. 297 - 307
3 Types
1. Passive Transport
2. Active Transport
3. Endocytosis/Exocytosis

2. Transport Across Cell Membranes pg. 297 - 307
1. Passive Transport

3. Brownian Motion and Concentration Gradients p. 297-298
Brownian Motion: matter is made up of tiny particles that are in constant motion

4. Molecules always move
1) randomly
2) from areas of high
concentration to areas of
low concentration
This is called DIFFUSION

5. Concentration Gradient
The difference in concentration between the high and low concentration areas. The greater the difference in concentration – the faster the particles move Eventually equilibrium is reached

6. Clips
H7_zkY diffusion of food coloring
TlNAT4 artistic

7. Why does this happen?
At high concentrations the molecules ricochet off of each other and move towards the area of low concentration

8. Equilibrium
Remember: at equilibrium the particles DO NOT stop moving, they continue to move back and forth across the concentration gradient.

9. Passive Transport pg. 297 - 303 NO ENERGY REQUIRED
Small molecules move by diffusion (water, oxygen, carbon dioxide)
When WATER molecules move by diffusion across a membrane we call it OSMOSIS

10. Tonicity of Solution pg. 299
Hypotonic more water than in the cell
Hypertonic less water than in the cell
Isotonic Same amount of water

11. Tonicity of Cell pg. 299
Hypotonic ?
Hypertonic ?
Isotonic ?

12. Clips
KAzYc egg cell osmosis

13. Should you drink salt water if you are lost at sea???
Potato Experiment

14. Should you drink salt water if you are lost at sea???

15. Facilitated Transport (also called facilitated diffusion)
Another form of passive transport
Used for molecules that are too large to cross the membrane by diffusion (i.e. glucose)

16. Facilitated Diffusion p. 303
Carrier proteins bind to larger molecules, and change their shape so molecules can diffuse through.
Channel proteins provide water filled pores for charged ions to pass through

17. Transport Across Cell Membranes pg. 297 - 307
3 Types
1. Passive Transport
2. Active Transport
3. Endocytosis/Exocytosis

18. Active Transport pg
Molecules move against the concentration gradient (low to high)
Energy must be provided (even when we are resting, 40% of our energy is spent on active transport!)

19. Active Transport
Uses specialized transport proteins and protein pumps

20. Why spend so much energy on active transport?
Maintains internal cell environments (i.e. cell’s electrical gradient, roots pull in minerals from soil, filtering blood in your kidneys)

21. Transport Across Cell Membranes pg. 297 - 307
3 Types
1. Passive Transport
2. Active Transport
3. Endocytosis/Exocytosis

22. Endocytosis/Exocytosis
For substances the cell needs to take in (endo = in) or expel (exo = out) that are too large for passive or active transport

23. Two Types of Endocytosis
1. phagocytosis (solids)
2. pinocytosis (liquids)

24. Test your transport knowledge!
02_int_membraneweb/