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Investigate the effects of different water potential sucrose solutions, on the size and weight of potato cylinders over the period of 48hours.

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Introduction

Osmosis in Plant Cells Aim: To investigate the effects of different water potential sucrose solutions, on the size and weight of potato cylinders over the period of 48hours. (Plant Cells) Prediction: From my background knowledge I predict that as the concentration of the sucrose solution that the potato cylinder is placed in increases, the size and weight of the potato cylinder will decrease over the period of 48hours, and vice versa, if sucrose solution concentration decreases, the potato cylinder should swell up and its size and weigh will increase. These predictions have scientific explanations. When a potato cylinder is placed in a high concentration sucrose solution where little water or no water at all is added, the potato cells under go a process called plasmolysis. Plant cells, in this case potato cells have a thick cell wall which is freely permeable and supports the cell; inside this cell wall is the protoplast which has a partially permeable plasma membrane. When the concentration of the surrounding solution in this case sucrose solution is high, it means that the solution potential surrounding the cell has very low water potential compared to the potato cell. (for plant cells water potential is a combination of solute potential and pressure potential which can be expressed as ? ...read more.

Middle

Apparatus: 1. Measuring Cylinder (25ml) 2. Syringe (5ml) 3. 5 Test tubes 4. Distilled water (25ml) 5. Sucrose solution 1 molar Concentration (25ml) 6. Beaker (50ml) 7. 5 potato cylinders (30mm width) 8. Scalpel 9. Electronic balancer 10. Accurate ruler for measurement (in mm) 11. Foil and tissue paper Method: * First stage is to cute the 5 potato cylinders accurately to width of 30mm using ruler and scalpel * We then measure the potato cylinders weight by placing each on the electronic balancer and recording the data * Second stage is to create the 5 different concentration solutes to pour into each test tubes by using the information on the table below: Test tube Concentration of sucrose solution Volume of distilled water (ml) Volume of 1molar sucrose (ml) 1 0 10 0 2 0.25 7.5 2.5 3 0.50 5 5 4 0.75 2.5 7.5 5 1 0 10 * After creating the solutions (10ml each), then we add each potato cylinders to each test tubes containing sucrose solution in order which I recorded their weight by * Then Secure each test tube by raping the end by aluminium foils * The test tubes are placed in a test tube holder and left for period of 48hours * After 48hours take out each potato cylinder in order and measure their size and weight and record them on the results table and calculate the differences in weight and size in mm and grams. ...read more.

Conclusion

Looking at my 0.5molar sucrose solution results, we can see a +0.1 g increase in weight, but looking at difference in size, there is a -1 mm decrease in size. This can be simple mistake in measurement using apparatus such as ruler and electronic balancer. Therefore to provide more accurate results and fair test, much more attention and concentration is required. * Using ruler to cut each potato cylinder is not very accurate since we have to rely on accuracy of human eyes which is simply not enough. In order to have exact equal size potato cylinders, mechanical machine cutters can be used. * Other factor which may have affected my results is the electronics balancer. The electronic balancer needs to be on a fully flat surface before use, because if it is moved to a different place, different results maybe given since the flatness of different surfaces are differ. * To produce different concentration solutions of sucrose, we again have to rely on our sight accuracy when using measuring cylinders to mix distilled water with sucrose (1molar). Simple inaccuracy may have effects on our results so to make this a fair test; more accurate apparatus which have much more accurate measurement can be used. Amin Shahiri 12AW Biology Osmosis Assignment 1 ...read more.

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