LabBench Activity

Exercise 3: Water Potential of Potato Cores

This activity is very similar to Exercise 2, except that you use cores from potatoes instead of dialysis bags. You submerge the cores in solutions of varying sucrose concentrations. When you calculate the percent change in mass, some of the cores will have gained weight while others will have lost weight, depending on the movement of water. You then graph this data and determine which concentration of the sucrose solution is in equilibrium with the cores. Since you know that the pressure potential of the surrounding solution in an open beaker is zero, you can now calculate the water potential.

animation

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For more information, review the section on Movement of Molecules in Cells.