1. Chapter 1.5 Transport Mechanisms Osmosis
Cells
Chapter 1.5
Transport Mechanisms
Osmosis

2. Osmosis
osmo- = water

3. Osmosis – A perfect definition!
THREE KEY IDEAS:
A net movement of water.
Occurs across a semi-permeable membrane
Water moves from an area of HIGH CONCENTRATION of water to an area of LOW CONCENTRATION of water.
Simply Perfect!

4. PASSIVE MOVEMENT OF WATER
2. Semi-permeable membrane
1. Net movement of water
3. Concentration gradient

5. TONICITY Tonicity compares concentrations of solute. 1 HYPOTONIC 2
ISOTONIC 3
HYPERTONIC

6. Word Work!
Hyper- = above, over, in excess Hypo- = low, under, beneath

7. HypOtonic Solution
Lower solutes in solution when compared to the cell. Causes water to ENTER cell and swell.

8. Isotonic Solution
Equal solutes in solution and cell. Equal movement of water in and out.

9. Hypertonic Solution
Greater solutes in solution when compared to the cell. Causes water to be drawn out of cell and shrink.

10. ‘Cell’ Bag Example

11. ‘Cell’ Bag Example

12. In Summary TONICITY SOLUTE CONC. WATER CONC. DIAGRAM HYPOTONIC LOW
HIGH
HYPERTONIC

13. REVISUAL!!!

14. Hypo to Hyper…

15. Osmosis in Living Organisms
Plant cells behave differently from animal cells when placed in solutions of different water concentrations.
Same water concentration
High water concentration
Low water concentration

16. REMEMBER

17. What is INCORRECT in the diagram below?
Pause and Think
What is INCORRECT in the diagram below?
HypOtonic

18. Hypo- , Hyper- or Iso- tonic?!
The cells below were placed in solutions of unknown concentration.
Determine the tonicity of each solution.

19. Effect of Osmosis on Cells

20. Diffusion vs. Osmosis

21. Pause and Think
Red blood cells are placed in solutions of different sugar concentration. Explain the result. (3)

22. Pause and Think
Fresh cherries are fleshy and juicy. Candied cherries are prepared by placing fresh cherries in a very strong sugar solution. Explain why candied cherries lose their fleshy texture. (3)

23. Let’s ANALYSE OSMOSIS EXPERIMENTS!!!

24. Experiment 1: The Potato Osmometer!

25. Experiment 1

26. What results would you expect to see after a few hours?
PREDICT:
What results would you expect to see after a few hours?
Salt Cavity
Sugar Cavity
Empty Cavity
Boiled +

27. Cavity fills with liquid Cavity fills with liquid
OBSERVE:
Cavity fills with liquid
Cavity fills with liquid
Cavity remains dry
Salt remains solid

28. Provide an explanation for each of the results that you observed.
EXPLAIN:
Provide an explanation for each of the results that you observed.
Salt Cavity
Sugar Cavity
Empty Cavity
Boiled +
The salt cavity provided a hypertonic external environment. Water in the cytosol of cells nearby exits the cell via osmosis from high concentration of water to low concentration of water. Therefore the escaping water filled the cavity, as observed.
The sugar cavity provided a hypertonic external environment. Water in the cytosol of cells nearby exits the cell via osmosis from high concentration of water to low concentration of water. Therefore the escaping water filled the cavity, as observed.
The empty cavity had no effect in the concentrations of solute inside or outside of cells. This environment was isotonic for cells and so there is no net movement of water into or out of the cell. The cavity therefore remains empty.
Boiling the potato results in destruction of the plasma membrane of cells. Membrane transport is not efficient and so water cannot travel to reach the salty cavity.

29. Experiment 2: Sliced Potatoes

30. Experiment 2

31. EXPLAIN:
Provide an explanation for the results that were observed in the picture.
Experiment
Result
Explanation
Potato in Distilled Water
Potato slice has a firm shape.
Potato in Salty Water
Potato slice bends easily.

32. Experiment 3: Celery

33. Experiment 3
Distilled Water
Salty Water
4 hours
4 hours

34. Celery in Distilled Water
EXPLAIN:
Provide an explanation for the results that were observed in the picture.
Experiment
Result
Explanation
Celery in Distilled Water
Celery in Salty Water

35. Experiment 4: Sugar Bags

36. Experiment 4 Determine the tonicity of the water in the beaker.
Determine the tonicity of the glucose solution in the dialysis tubing.
Will water move INTO or OUT of the dialysis tubing? Explain.
Will glucose move INTO or OUT of the dialysis tubing? Explain.

37. Experiment 4 - Answers
Determine the tonicity of the water in the beaker.
Determine the tonicity of the glucose solution in the dialysis tubing.
Will water move INTO or OUT of the dialysis tubing? Explain.
Will glucose move INTO or OUT of the dialysis tubing? Explain.
hypotonic
hypertonic IN
NO MOVEMENT because too LARGE!

38. Experiment 5: Egg Osmosis

39. concentrated salt solution
Experiment 5
concentrated salt solution
water
egg contents
egg contents
After 2 days

40. Celery in Salt Solution
EXPLAIN:
Provide an explanation for the results that were observed in the picture.
Experiment
Result
Explanation
Egg in Distilled Water
Celery in Salt Solution