Part 1A

1. Which substances are entering the bag and which are leaving the bag ? What experimental evidence supports your answer?

2. Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion.

3. Quantitative data uses numbers to measure observed changes. How could this experiment be modified so that quantitative data could be collected to show that water diffused into the dialysis bag?

4. Based on your observations, rank the following by relative size, beginning with the smallest: glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules.

5. What results would you expect if the experiment started with a glucose and IKI solution inside the bag and only starch and water outside? Why?

Part 1B

6. Explain the relationship between the change in mass and the molarity of sucrose within the dialysis bag.

7. Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4 M sucrose solution instead of distilled water. Explain your response.

8. Why did you calculate the percent change in mass rather than simply using the change in mass?

Part 1C

9. Determine the molar concentration of the potato core.

Part 1D

10. If a potato core is allowed to dehydrate by sitting in the open air, would the water potential of the potato cells increase or decrease? Why?

11. If a plant cell has a lower water potential than its surrounding environment and if pressure is equal to zero, is the cell hypertonic (in terms of solute concentration) or hypotonic to its environment? Will the cell gain water or lose water? Explain your response.

12. A beaker contains a dialysis bag containing a 0.1 % sucrose solution (psis = -1, psip = 0)submerged in a 0.4 % sucrose solution (psis = -4). If the beaker is open to the atmosphere, what is the pressure potential of the system? Is the greatest water potential inside the beaker or the dialysis bag? Will water move into or out of the bag?

13. Zucchini cores placed in sucrose solutions at 27oC resulted in the following percent changes after 24 hours:

% change in mass [Sucrose]
20 distilled water
10 0.2 M
-3 0.4 M
-17 0.6 M
-25 0.8 M
-30 1.0 M

Graph the results and find the molar concentration of solutes within the zucchini cells. Calculate the solute potential of the sucrose solution in which the mass of the zucchini cores does not change. Calculate the water potential of the solutes within the zucchini cores.

14. What effect does the addition of solute have on the solute potential component of that solution?