Name:______Per:______Date:______

Potato Lab: Passive Transport

Read all directions carefully before completing this lab.

Purpose: to observe the effects of placing a cell in hypertonic and hypotonic solutions.

Materials:

one potatobalance

paper cupgraduated cylinder

1M sucrose ruler

water

Procedure:

  1. Day 1
  2. Obtain a paper cup and label it with the names of the members in your group.
  3. Use your group number and the table below to calculate how much water and how much syrup to add to your cup.

Group 1 / Group 2 / Group 3 / Group 4 / Group 5 / Group 6
Concentration of solution / 0 M / 0.2 M / 0.4 M / 0.6 M / 0.8 M / 1.0 M
% Water / 100 / 80 / 60 / 40 / 20 / 0
% Sucrose / 0 / 20 / 40 / 60 / 80 / 100

_____ mL H2O+_____ mL 1M sucrose=400 mL total vol.

  1. Record your hypothesis for this experiment. What will happen to the potato when left overnight in your water/sucrose solution? Will it shrink, expand, or stay the same?

______

______

  1. Use the graduated cylinder to measure out the appropriate amounts of water and sucrose solution. Add the water and sugar solutions to your paper cup and mix.
  2. Use a cork borer to cut 5 potato cylinders. Cut each cylinder to length of 3 cm.
  3. Determine the mass of all 5 potato cylinders together and recordit in the data table below.
  4. Place all 5 potato cylinders in the water/sucrose solution. Make sure that the potato cylindersare completely submerged. Cover loosely with plastic wrap and place cup in designated area to let stand overnight.
  5. Clean up your table. Return all materials and safety equipment. Wash your hands.
  1. Day 2
  2. Remove potato cylinders from paper cup.
  3. Determine the mass of all 5 potato cylinders together and record it in your data table.
  4. Discard potatoes, water/sucrose solution, and paper cup.
  5. Calculate the % Change in Mass of your potatoes and record it in your data table.

% Change in Mass = (Massfinal – Massinitial) / Massinitialx 100

  1. Complete your data table by recording the % Change in Mass for all other groups. You will need this data in order to graph the effect of sucrose concentration on the mass of the potato and, ultimately, to interpolate the concentration of solute inside the potato (our model cell).

Change in Mass of Potato in Various Sucrose Solutions

Concentration of Sucrose Solution / Initial Mass (g) / Final Mass (g) / % Change in Mass
0%[*]
20%
40%
60%
80%
100%[†]

Potato Lab: Passive Transport

Analysis (on separate sheet of paper)

  1. Make a graph showing the effect of sucrose concentration on the % change in mass of the potato. Draw a BEST FIT LINE for your data. (HINT: Make “% change in mass” your Y-axis and “% sucrose concentration” your X-axis. You should have data points at 0% sucrose, 20% sucrose, 40% sucrose, 60% sucrose, 80% sucrose, and 100% sucrose corresponding to the potatoes for Groups 1-6)
  1. What happens to a cell in a hypertonic solution? Explain your answer.
  1. What happens to a cell in a hypotonic solution? Explain your answer.
  1. How does this information help explain what you observed in this lab?
  1. Use your best fit line to estimate the solute concentration of the raw potato. (HINT: This will be the % at which your best fit line intercepts the X-axis).

Conclusion (on same sheet as Analysis)

  • Paragraph 1 – Restate your hypothesis. Was your hypothesis supported by your data? Explain.
  • Paragraph 2 – Error analysis. Describe at least two sources of error in the lab. What could have affected your results?
  • Paragraph 3 – Explain in detail what happened to ONE of the six potatoes in the lab. Use the following terms: osmosis, concentration gradient, hypertonic/hypotonic/isotonic solution.
  • Make a sketch of the potato cell showing the areas of high and low water concentration, and the direction of the net movement of water.

The analysis and conclusion for this lab are due at the start of class on Wednesday, 11/3.

[*]Pure water

[†] 1M sucrose