AP Biology—Unit 2
Water Potential Pre-Lab
Name:
Directions:
Please read the background information from the College Board AP Biology Laboratory Manual and complete
the following pre-lab questions.
1. Define Diffusion.
2. What happens in equilibrium?
3. Define Osmosis.
4. What determines if a substance can pass through a semi-permeable membrane?
5. Explain what it means when two solutions are isotonic and discuss the net direction of the water flow.
6. Discuss the difference between hypertonic and hypotonic solutions and discuss the net direction of the
water flow.
7. What would happen if you applied salt water to the roots of a plant? Why?
8. A dialysis bag contains a sucrose solution of 0.6 M. The beaker into which it is placed has a 0.3M
sucrose solution. Is the dialysis tubing hypertonic or hypotonic to the beaker solution? In which
direction is the water expected to go?
9. What does water potential measure?
10. What are two components that influence water potential?
11. What is turgor pressure?
12. Will water move into or out of a plant cell if the cell has a higher water potential than its surrounding
environment?
13. Calculate the solute potential of a 0.1M NaCl solution at 25°C.
a. If the concentration of NaCl inside the plant cell is 0.15M, which way will the water diffuse if
the cell is placed into the 0.1M NaCl solution?
b. What must turgor pressure equal if there is no net diffusion between the solution and the cell?
14. If a potato core is placed in pure water, what direction will water flow? Why?
15. Discuss the difference between animal and plant cell response when placed in hypotonic solutions.
16. Does increasing pressure increase or decrease water potential? Explain.
17. Does increasing solute concentration increase or decrease water potential? Explain.
18. Will water go from area of -3 water potential to one of 0 water potential or vise versa? Explain.