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To Investigate the Movement of Osmosis Through a Potato Sample.

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Introduction

Osmosis Aim: to investigate the movement of osmosis through a potato sample. Hypothesis: Osmosis is the movement of water through a semi permeable membrane, separating solutions of different concentrations. The water passes from a region of high concentration to a region of low concentration, until the two concentrations are equal in concentrations of water. Many cell membranes behave as semi permeable membranes, and osmosis is a vital mechanism in the transport of fluids in living organisms, for example, in the transport of water from the soil to the roots in plants. If a cell is in contact with a solution of lower water concentration than its own contents, then water leaves the cell by osmosis, through the cell membrane. Water is lost first from the cytoplasm, then the vacuole through the tonoplast. The living contents of the cell contracts and eventually pulls away from the cell wall and shrinks, this is known as Plasmolysis. If you put a plant cell in water, water enters by Osmosis, then swells up. However, the cell will not burst. This is due to the fact that the cell walls are made from cellulose, which is extremely strong. Eventually, the cell stops swelling, and when this point is reached, we say the cell is turgid. This is important, because it makes plant stems strong and upright. Osmosis diagram: I predict, that as concentration increases, the weight of the potato will decrease. ...read more.

Middle

For organisation's sake, we set up all of the test tubes at once, and labelled them individually to avoid confusion later on. Into each test tube, we poured 15mls of Glucose solution, and added one of the potato chips, each weighing around 1 gram, and measuring 33mm by 5mm. In order to make it as much of a fair test as possible, we added the potato chips very quickly, to make sure one chip didn't have a longer amount of time in the solution than another. We then left each one for 30 minutes. After 30 minutes, we emptied each test tube, leaving only the potato chips inside. Before we measured and weighed each chip, we dabbed them with paper towel. If we had of left excess water on the chips, the weights would not be accurate. We then measured the chips in mms because they are a more accurate measurement. Results Analysis Of Graphs: * Graph 3 'Average change in weight' is quite confusing. For example, the result I obtained for 0.1 molar concentration does not follow the pattern of the other results. It is not possible that the weight could have gone up more for 0.1 molar concentration, compared to 0 molar. This could be due to having excess water on the potato chip when weighing or because of misreading the scales. Conclusion: To conclude this investigation, I can say that the movement of water through a selectively permeable membrane is affected by concentration of glucose solution, or by any other solution. ...read more.

Conclusion

When weighing the potato chips after 30 minutes in solutions, it was inevitable that they would have excess water on them, and so we dabbed them with paper towel to remove it. However, in doing this we could have removed water that was not excess, and altered our results. Another inaccuracy was when we put the potato chips into the solutions, because it was impossible to not leave a small interval between each test tube. The first test would have been going for a few seconds longer than the last. I do not know how I would resolve this problem. I also found 2 anomalous results. The first, was on the graph which showed average change in width, the anomalous result was for the test for 0.2 molar solution. The second was on the graph that showed average change in weight, the anomalous result was for the test with 0.1 molar concentration. The main reason for this is inaccuracy. I used the mean when plotting my graphs. That way, the information is clear and can be understood quickly, however, the disadvantage of this, is the fact that if one of the two results is inaccurate, the mean will also be. I believe that this is the reason for the anomalous results. I could extend this AT1 by investigating osmosis with a different factor as opposed to concentration of water. I could investigate the effects of temperature on osmosis, or surface area. This would give me a very clear understanding and knowledge of osmosis in potatoes. ...read more.

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