1. Do Now Complete Do Now sheet Answer:
Two molecules, A and B, and their distribution inside and outside of a cell are represented in the diagram.
State one possible reason why molecule A could diffuse across the membrane of the cell but molecule B could not.
Answer:
Molecule A is small enough to pass, molecule B is too big.

2. Aim: How do Osmosis and Diffusion compare?

3. What is the diffusion of water called?
Osmosis

4. OSMOSIS
The movement of water from an area of high concentration to an area of less concentration.

5. What is meant by concentration?
The amount of solute!
Solvent: The liquid (ex. Water)
Solute: The solid added to the liquid (ex. Salt/sugar)
Distilled water
100% pure water

6. Concentration Differences:
1) A 90% salt solution vs. a 20% salt solution
Which solution has more salt particles?
Which solution has more water molecules?
2) A 60% salt solution vs. 80% salt solution?

7. Which container has a greater concentration of water molecules?
= Solute (salt)
= Solvent (water)
Which container has a greater concentration of solute molecules?

8. In which direction is osmosis going to occur?
= Solute (sugar)
= Solvent (water)
Selectively Permeable

9. Why does this happen?

10. Why are the water molecules diffusing to the left?
Water molecules are red

11. The water is moving from an area of high to low!

12. Why does water go in and out of the cell?
If solute is equal, then so is water amt., molecules still move back and forth!
To maintain DYNAMIC EQUILIBRIUM

13. What happens to an animal cell if it is surrounded by a low concentration of water?
The Cell will shrink!! Salt sucks!!!!

14. Practice Questions
1. A cell containing 98% water in its cytoplasm is placed in a 20% salt solution. What will happen to the cell?
2. What will happen to a cell if it is placed into a concentrated salt solution?
3. What will happen if a cell is placed in distilled water?

15. In which direction will osmosis happen?

16. How is osmosis a form of passive transport?
Osmosis is the movement of water from an area of high concentration to an area of low concentration. No ATP needed.