1. Cell Membrane
Fig. 3.6

2. Phospholipids
Prevents movement of water soluble molecules and ions

3. Cholesterol
Strengthens cell membrane

4. Integral Proteins
Form channels to allow molecules or ions to enter or leave the cell

5. Recognition Proteins
Carbohydrate
Identify the cell

6. Peripheral Protein
Enzymes

7. Receptor Proteins
Reacts with molecular signals

8. Transport of Materials across the Cell Membrane

9. Why a cell needs transport ?
for obtaining useful materials, and
for eliminating metabolic waste
Permeability
living cell membrane - selectively permeable
visking tubing / dialysis tubing selectively permeable
dead cell membrane - freely permeable
cell wall (non-living) - freely permeable

10. Diffusion or Passive Transport
molecules move from high concentration to low concentration area
(fluid/dissolved solid molecules)

11. General direction of water movement
low solute
concentration
high solute
concentration
low water
concentration
high water
concentration

12. Factors affecting Rate of Diffusion
Size (larger size, slower rate) (steeper gradient, faster rate)
Temperature (higher temp, faster rate)
Concentration gradient (concentration difference between the two areas)
Medium (gas > liquid > solid)
Surface area (larger area, faster rate)

13. Importance of diffusion to living organisms
get rid of waste products
involve in gaseous exchange during respiration
absorb mineral salts in plants
absorb digested food in mammals

14. Osmosis
water / solvent molecules move from high water concentration to low water concentration area (high water potential to low water potential area) (low solute concentration to high solute concentration area) through a selectively permeable membrane

15. Active Transport
molecules move from low concentration to high concentration area
requires energy & carrier
occurs in living cells only
also transport from high to low concentration in high rate

16. Active Transport
outside
carrier molecule
cell membrane
substances
inside
Substances passes through the carrier from outside (low conc.) to inside (high conc.)

17. Fig. 3.17a

18. Fig. 3.17b

19. Cell in a Hyperosmotic Solution
350
Crenate
300

20. Cell in a Hypoosmotic Solution
Swell
250
300
Lyse

21. Cell in Isosmotic Solution
No net movement of water
300
300
0.9%
0.9%