1. Homeostasis and CellTransport
Mr. Hamer's Halophiles

2. Transport through cell membranes
The phospholipid bilayer is a great barrier around cells. However, for the cell to survive some materials need to be able to enter and leave the cell.
There are 4 basic mechanisms:
Diffusion
Osmosis
Facilitated diffusion
Active transport

3. Diffusion of liquids

4. Diffusion is the net movement of substances from a region of their high concentration to a region of their lower concentration. The molecules move down a concentration gradient. As a result of diffusion, molecules reach equilibrium This is where they are evenly spread out, and there is no net movement of molecules from either side.

5. DIFFUSION
Diffusion is a PASSIVE process which means no energy is used to make the molecules move.

6. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell

7. Diffusion through a membrane
Cell membrane
diffusion
Outside cell
Inside cell

8. Diffusion through a membrane
Cell membrane
Outside cell
Inside cell
EQUILIBRIUM

11. Molecules that diffuse through cell membranes
Oxygen is non-polar so diffuses very quickly.
Carbon dioxide is polar but very small so diffuses quickly.
Water is polar but also very small so diffuses quickly.

12. Facilitated diffusion
Large polar molecules like glucose and amino acids cannot diffuse across the membrane.
These types of molecules pass through protein channels instead. This is called FACILITATED DIFFUSION.

14. Facilitated Diffusion through a membrane
Cell membrane
Protein channel
Outside cell
Inside cell

15. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell

16. Facilitated Diffusion through a membrane
Cell membrane
diffusion
Protein channel
Outside cell
Inside cell
EQUILIBRIUM

18. Facilitated diffusion

19. Osmosis
The diffusion of water from an area of high concentration of water molecules to an area of low concentration of water across a selectively permeable membrane.

20. Osmosis CONCENTRATED SOLUTION DILUTE SOLUTION
Cell membrane partially permeable.
Sugar molecule
VERY Low conc. of water molecules. High water potential.
VERY High conc. of water molecules. High water potential.
Outside cell
Inside cell

21. Osmosis Cell membrane partially permeable.
Low conc. of water molecules. High water potential.
OSMOSIS
High conc. of water molecules. High water potential.
Outside cell
Inside cell

22. Osmosis Cell membrane partially permeable. OSMOSIS Outside cell
Inside cell
EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water