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To find out how the concentration of sugar (sucrose) inside a potato is effected by Osmosis.

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Introduction

Osmosis - GCSE Biology Aim To find out how the concentration of sugar (sucrose) inside a potato is effected by Osmosis. Osmosis Osmosis is the movement of water through a semi-permeable membrane from a region where there is a high concentration of water molecules to a region where there is a low concentration of water molecules. The water moves through a semi-permeable membrane from the dilute solution to the concentrated solution. The process stops when the concentrations on both sides of the membrane are the same, this is called the isotonic point. Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell. Hypertonic Solutions contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. Hypotonic Solutions contain a low concentration of solute relative to another solution. When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell. An example of osmosis is in the transport of water from the soil to the roots in plants. ...read more.

Middle

experiment accurately * Repeat the experiment several times in case of abnormal results * Make sure the potato chips are equal in length * Use the same amount of sucrose solution for each test tube (20 ml) * Make sure all the experiments are done at the same room temperature. Safety must be taken into consideration when using the knife blade to cut the potatoes, a cutting tile must be used. Test tubes will need to be placed into test tube racks away from the edge of the table. Results Concentration of Test Initial Mass Final Mass Percentage Change Average Percentage Sucrose Solution (M) Tube of Chips (g) of Chips (g) In Mass Change 1 7.55 6.55 13.25 4.52 0.2 2 7.22 7.08 0.14 1.55 3 7.48 7.31 0.17 1 8.19 7.9 0.29 0.4 2 7.94 7.69 0.25 0.28 3 7.63 7.33 0.30 1 7.59 6.79 -0.80 0.6 2 8.12 7.38 -0.74 -1.82 3 7.88 7.03 -0.85 1 8.36 7.08 -1.28 0.8 2 8.21 7.11 -1.10 -2.68 3 7.79 6.89 -0.90 Analysis From my results I can see the movement of water through a semi-permeable membrane is affected by the concentration of the glucose solution or by any other solution, therefore my prediction was correct. ...read more.

Conclusion

I would also cut the chips fresh instead of storing them in distilled water. As the chips are stored in distilled water, osmosis may have already started to take place. My results could be improved by using a water bath to make sure the temperature of the experiment is the same and constant, instead of at room temperature. The exact isotonic point could be found by carrying out more experiments with solutions with concentrations closer to my estimated isotonic point of 0.4M. However I think the results from the experiments are still fairly accurate. This is because I repeated each concentration of solution three times, therefore an average could be worked out and anomalous results could be spotted. My first test tube with the 0.4M solution was an anomalous result. This may have been due to when the potato was dried to remove surface water paper towels were used which could unevenly dry the potato chips therefore it could affect the outcome of the experiment. The chip may have been the wrong size or the temperature of the experiment may have affected the results. The line of best fit is fairly close to all of my results on the graph. Therefore this shows that the experiment was fairly accurate. The anomalous result was so extreme that it did not even fit on the graph. ...read more.

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