Osmosis in Potato Tubers Essay

1251 Words Aug 16th, 2008 6 Pages
Osmosis in Potato Tubers

Andrew Dickson Background
When a plant cell is bathed in a solution of the same concentration (isotonic) as its intracellular environment, its mass and volume remain the same. This is because water enters and leaves the cells at the same rate. There is no net loss or gain of water by osmosis.
Samples of cells can be placed in a range of solutions of different concentration. The cells will gain water by osmosis when placed in solutions which are more dilute (hypotonic) than the intracellular environment. They will therefore gain mass. The cells will lose water in those solutions that are more concentrated (hypertonic) than the intracellular environment and so lose mass. The concentration of the
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Cut off the ends if there is potato skin present
5. Place the cylinders on pieces of filter paper labeled in pencil with the concentrations of sucrose corresponding to the solution the cylinder will be placed in
6. Dry each cylinder on the filter paper dabbing (no squeezing/pressing allowed)
7. Record the mass of each cylinder on its own. A pre-weighed Petri dish will be present on the balance to keep it clean. Make sure the balance is zeroed before you weigh
8. Transfer the pairs of cylinders to the appropriate boiling tube with forceps
9. Stopper the tubes. Note the time
10. After 30 minutes remove the cylinders from the tubes in turn, using the same order that you inserted them. Note the time
11. Remove any surplus fluid quickly and gently dab with filter paper. Do not squeeze the cylinders or they will loose all water. Reweigh the cylinders. Record their mass. Record any observations you make about changes in the nature of the cylinders in your table
12. Work out % change in mass of each pair of cylinders. Record this in your table.
13. % change in mass = change in mass/original mass x 100%

Test Tube Sucrose Concentration (%) Mass of potato cylinder (g) Mass of potato cylinder after (g) Changes in mass (g) Percentage change in mass (%)
A 0% 3.66 3.74 0.08 2.10%
B 5% 3.47 3.53 0.06 1.73%
C 10% 3.79 3.8 0.01 0.27%
D 15% 3.66 3.45 -0.21 -5.73%
E 20% 3.99 3.75 -0.24 -6.02%

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