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In this experiment we are going to be studying the affects of Osmosis in Potatoes. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.

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Introduction

Background In this experiment we are going to be studying the affects of Osmosis in Potatoes. Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. A semi-permeable membrane is a very a very thin layer of material, cell membranes are semi-permeable. These will allow some things to pass through, but will prevent other things from passing through. For example, cell membranes will allow small molecules such as Oxygen, water, Carbon Dioxide, Ammonia, Glucose, amino acids, etc. to pass through. But they will not allow larger molecules such as Sucrose, Starch, and protein, etc. to pass through. A region of high concentration of water is either a very dilute solution of, for example, sucrose, or Pure Water. In each case there is a lot of water: there is a high concentration of water. A region of low concentration of water is a concentrated solution of something, for example, sucrose. ...read more.

Middle

I am going to have 6 different test tubes which will have the same volumes but different concentrations. These concentrations will be diluted water, 0.2M, 0.4M, 0.6M, 0.8M and 1.0M. Method I started off getting a large potato. Using a cork borough I removed 12 sections of Potato, I used the cork borough on a tile and kept my hands well away from it so I would not cut myself. I then cut these sections down using a razor blade on a tile so they were all 4 cm long; I measured this using a ruler. I used the razor blade with precaution, taking into account that it was sharp and making sure I did not cut myself. After this I weighed each individual section on a weighing machine, this scale measures down to 0.00g. I then got 6 test tubes and filled them with different concentrations of salt solution; each test tube had a 30cm volume of liquid. ...read more.

Conclusion

Because there is more water in the cells than in the solution, more water is going to pass through the cell membrane from the cells than pass though in to them. Therefore the cells will shrink and the overall mass and size of the potato section will decrease. The larger the concentration of the salt solution the larger amount of water will pass from the cells into the solution; this is why the cells decrease in size the larger the concentration. Earlier Work While in the forth form I did work on Osmosis. The experiment helped me out a lot with the understanding of Osmosis. In the experiment a high concentration of salt solution is put into some dialysis tubing, which is a semi-permeable membrane. The tubing is tied up and placed into some Distilled water. It is left for a few days, and when we came back, the distilled water is tested and it is now a low concentration of salt solution. The text book GCSE Biology second edition by D.G. Mackean also helped me with my understanding of Osmosis. ...read more.

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