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Osmosis investigation: Osmosis in potato cells.

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Introduction

Osmosis investigation: Osmosis in potato cells Aim The aim of my experiment is to investigate the effect of glucose solution on osmosis in potato chips. I shall be observing how the mass of the potato chip changes in different concentrations of glucose solutions. Simply, will the effect of the action of osmosis be affected by the concentration of the solution? Introduction Knowing that osmosis (a diffusion of water) will occur across a semi-permeable membrane whenever there is a difference between the water concentrations on the two sides of the membrane, and knowing that when this happens to cells they will either become turgid if water flows into them, or plasmolysed if water flows out of them, and thus change their volume, we want to test the hypothesis that: If the concentration of a solution into which a cylinder of potato is placed is greater than a certain level the cylinder will contract, and if the concentration is less than that level it will expand. Apparatus For the experiment I will require: Potato - to use to show osmosis Borer - to cut circular potato pieces Scalpel. (To allow us to make our own). Solutions of varying strengths, a solution of a known strength and distilled water. ...read more.

Middle

If the solution is a stronger concentration of glucose osmosis will work in reverse in that water will be drawn out of the potato cells into the solution. The cells will become plasmotised as it loses mass. When the water osmoses into the potato chip cell they become turgid. The potato chip will become rigid when turgid. Fair test. 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 sucrose solution. For the purpose of my experiment I am going to carry out all the experiments at the same time so the temperature is kept almost the same throughout. The mass of the potato is a dependent variable. This means that it will be measured throughout the experiment. I will measure the mass in grams. The potato chip will be measured before it is put in the solution, and after. This will allow us to see whether osmosis has taken place, and to what extent. The volume of the solution that the potato chips are kept in must be the same. The potato chip must be totally covered in the solution, and the amount of solution will be kept the same because all the potato chips will be the same size. ...read more.

Conclusion

accurate weight measurement. The test might also be more accurate if the potato cylinders were left in the solutions for a longer period of time to allow the solution to penetrate fully to the core of the sample. The test could also be repeated more times for each concentration of solution, and with a greater number of concentrations, as this would decrease the error - a disadvantage of our experiment was that one anomalous result affected the others significantly. Results that were not as I would have expected occurred, the range of results appeared too low. However, although this is apparently an anomalous result, it could have been caused by either experimental error - more significant when a small number of results are used, or a difference in the potato for those cylinders. Either of these would easily be recognized if a larger number of results were collected and used. For future experimentation we could repeat this experiment using a range of solution strengths very close to the value discovered here of sap osmolarity, to define more exactly its true value. We could also extend the experiment to use tissue samples from other plants, to discover whether the hypothesis is also correct for other tubers, and even for other plant tissues. We would then also be able to compare osmotic pressures inside different plants. ...read more.

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