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An Investigation into factors affecting Osmosis in Potato Tissue

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Introduction

An Investigation into factors affecting Osmosis in Potato Tissue PLAN I am investigating the factors which directly affect the process of osmosis. I will be using potato tissue and sugar solutions to do this. Osmosis is the process by which water molecules move from one cell to another, in living systems, across a partially permeable membrane, from a region of high water concentration to a region of low water concentration. A partially permeable membrane allows small molecules like water to pass through it, but does not allow larger molecules like glucose to pass through it. Aim: My aim is to investigate the effect osmosis has on the mass and length of potato tissue and to investigate what effect varying the concentration of the sucrose solution surrounding the potato tissue, has on it. I also intend on working out the isotonic point, the point where osmosis does not occur because there is no net movement of water because the concentration on the outside of the potato, is the same as that on the inside. To create a fair test certain aspects of the experiment will have to be kept the same whilst one key variable is changed. I have chosen to vary the concentration of the sugar solution surrounding the potato tissue. The following factors are those which I must keep constant throughout the experiment as they may affect osmosis: � Temperature- I will perform the experiment at room temperature. � Cultivar of potato. � Length, surface area and volume of potato chips- I will use Vernier callipers. � Angle potatos are cut in- I will cut them at right angles. ...read more.

Middle

2.29 2.2 5 4.8 2.31 2.27 5 4.9 0.4 2.29 1.89 5 4.7 2.27 1.94 5 4.6 2.33 1.99 5 4.8 0.6 2.32 1.62 5 4.5 2.35 1.74 5 4.6 2.23 1.64 5 4.6 0.8 2.28 1.71 5 4.5 2.24 1.54 5 4.5 2.35 1.71 5 4.6 1 2.34 1.63 5 4.5 2.26 1.43 5 4.6 2.42 1.49 5 4.4 The following table shows the mass and length changes of the cylinders: Conc. Mass Change(g) Length Change(cm) % Mass Change % Length Change 0 0.24 0.2 10.13 4 0.25 0.3 10.37 6 0.23 0 10.04 0 0.2 -0.03 0.1 -1.28 2 0.07 0 3.06 0 -0.01 0.1 -0.43 2 0.3 -0.11 -0.1 -4.64 -2 -0.09 -0.2 -3.9 -4 -0.04 -0.1 -1.73 -2 0.4 -0.4 -0.3 -17.46 -6 -0.33 -0.4 -14.54 -8 -0.34 -0.2 -14.59 -4 0.6 -0.7 -0.5 -30.17 -10 -0.61 -0.4 -25.96 -8 -0.59 -0.4 -26.46 -8 0.8 -0.57 -0.5 -25 -10 -0.7 -0.5 -31.25 -10 -0.64 -0.4 -27.23 -8 1 -0.71 -0.5 -30.34 -10 -0.83 -0.4 -36.73 -8 -0.93 -0.6 -38.43 -12 When I refer to 'conc.', I mean the concentration of sucrose solution. Also, for each concentration, I have 3 sets of results, as these are for the 3 different potato cylinders I used for each sucrose concentration. The following table is that which I will use to draw my conclusions from. I have averaged the percentage mass and length change for the 3 cylinders I used for each concentration. Conc. Average % Mass Change Average % Length Change 0 10.18 3.33 0.2 0.45 1.33 0.3 -3.42 -2.67 0.4 -15.53 -6 0.6 -27.53 -8.67 0.8 -27.83 -9.33 1 -35.17 -10 ANALYSIS I have decided that the best way of presenting my results is by constructing a line graph, with a line of best fit as well as by joining the points. ...read more.

Conclusion

I would improve on the experiment by using a pipette to measure out the volumes of sucrose and water. I think that the experiment is actually quite reliable. If you look at my results tables, all the replicates for each concentration give pretty much the same results. I do not think the experiment was very suitable. This is because plasmolysis takes place after a certain concentration, so it is difficult to establish a trend when this happens. Also, the percentage mass and length change should be approximately the same at least, but looking at my table, most of the time the percentage values are not even similar. I think this may be because he experiment is not suitable. I think it would be very interesting to do the experiment again with many improvements and modifications. I think it would be interesting to use more sucrose concentrations, especially around 2.22, the value I found to be the isotonic point. I think I would be able to find a more accurate value. It would also be better to use more replicates. I would also use more accurate equipment, mainly a pipette rather than a measuring cylinder. I think with the new experiment, up till the point of plasmolysis, I may be able to get a line of best fit that runs very close by all the points. I think it would also be interesting to investigate more about plasmolysis, and the point where the cell tissue plasmolyses. I could use more concentrations around 0.6, the point I approximate to be where the potato tissue starts to plasmolyse. It would also be interesting to use a different plant tissue, possibly a similar root crop. I think the pattern would be the same, but the actual values and the isotonic point, would be different. Faizal Patel 5/3/2007 - 1 - ...read more.

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