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Investigating the effect of different concentrations of sucrose solutions on potato tuber cells.

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Introduction

Investigating the effect of different concentrations of sucrose solutions on potato tuber cells Plan: Aim: To find out what effect different concentration of sugar solutions have on potato tuber cells. Background information: What is osmosis: Osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane. A partially permeable membrane is a thin layer of cells which allow only small molecules like oxygen, carbon dioxide and water to pass through easily but not larger molecules. Preliminary work: In past science lessons, we have done experiments to test osmosis. We proved that it takes place by doing three experiments. We have learnt that osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane. I am going to use these past experiments and their results to help me with my prediction for this experiment. When water moves into a cell, the cell grows in mass and length and becomes turgid and if this is left too long, the cell may burst. When water moves out of a cell, the cell shrinks in mass and length and becomes "floppy". Turgid cell. Bursting turgid cell. "Floppy" cell. Preliminary Experiments Experiment 1: I put three potato cylinders of equal length into three equal amounts of sugar solution and left them for equal amounts of time before recording the results. Diagram This experiment could have been improved by a wider range of solutions to give me more accurate results. This could also have been achieved by doing repeats and measuring the potatoes mass as well as length. Experiment 2: I used visking tubing to represent a partially permeable membrane. I filled it with a concentrated sugar solution, which represented cytoplasm and placed it into water. I then left it and recorded the results. Diagram The visking tubing expanded as the water molecules had travelled across the visking tubing membrane into the sugar solution, as it was more concentrated than the water outside the tubing. ...read more.

Middle

I will then measure the masses of all the potato chips to make sure they are the same. I will then measure out all of the solutions using different measuring cylinders for each so I do not contaminate them using the same amount of solution in each and pour them one each into my equal sized test tubes before placing the potato chips inside the test tubes one of each length in each. I will them place them in a test tube rack. I will then coven the test tubes with clung film to prevent evaporation before leaving them in the same place for 24 hours. I will then record the results at the same time to prevent any of the chips drying out and therefore, changing the reliability of my results. I will put cling film on the top because when I did the same experiment with 3 solutions, some of the solutions evaporated, I am using two potato chips in each solution so that I can find an average percentage change as my results in the experiment with the three solutions were not very accurate. Results: I did the experiment safely, as planned and measured the length and mass of the potato chips making sure to clean up any spilt solution. I have recorded my results into the table below and calculated the percentage change. A Table to show the % change in Length and Mass of Potato Tuber Cells after they have been placed into different solutions Sugar solutions Length (mm) Mass (g) Average percentage change in Length in Mass Before the experiment 20.0 10.0 Average 1.1g 0.5g Average 0.0% 0.0% Distilled Water 24.0 13.0 19.0 1.5 0.7 1.1 25.0% 38.0% 0.2 Molar 20.0 12.0 16.0 1.1 0.5 1.6 10.0% 0.0% 0.4 Molar 20.0 12.0 16.0 1.0 0.5 0.8 10.0% -2.5% 0.6 Molar 19.0 10.0 14.5 0.7 0.3 0.5 7.5% -38.0% 0.8 Molar 19.0 10.0 14.5 0.8 0.5 0.7 -2.5% -13.5% 1.0 molar 19.0 9.0 14.0 0.7 0.3 0.5 -7.5% -38.0% ...read more.

Conclusion

Evaluation: The method I used allowed me to investigate osmosis in potato tuber cells because I could easily see if osmosis had occurred in the potatoes in the different solutions and also how much water had travelled though the partially permeable membrane and whether it had travelled into or out of the potato due to osmosis. My results followed the expected trend except for the potato in the 0.6 molar sugar solution, which shrank more in length than I expected. This could have been because I may have left the other potato chips to dry out for longer and so the potato chip in the 0.6M sugar solution contained more water so more travelled out causing it to loose more mass and length than I expected. If I were to do this experiment again, I would use different test tubes for the repeats because as the potato chips in the same test tubes are affecting the amount of surface area available to water particles for osmosis as wherever you put the repeat, it is always blocking one side of the potato chip causing the results to be unreliable. Another way to improve this experiment is to make sure that the potato chips are cut, measured and weighed at about the same time otherwise; they may dry out and change in mass before they are even put into the solutions. My results are mostly reliable as they present the expected trend and support the drawn conclusion except for the anomalous result (0.6M) because osmosis occurred as expected. Further experiments will provide additional results about in osmosis in potato tuber cells by investigating osmosis to a greater degree. I should carry out more experiments on the middle two solutions i.e. 0.4M and 0.6M to make sure that I can obtain correct information as to what exactly happens to potato chips placed into these solutions. Jemma Robertson 10D Mrs. Summerfield ...read more.

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