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Investigating the factors affecting the rate of osmosis in potato cells.

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Introduction

Investigating the factors affecting the rate of osmosis in potato cells Introduction Osmosis is a physical process that occurs in plant and animal cells when there are molecules in a high concentration inside (or outside) the cell, and there is a low concentration outside (or inside) the cell. The process which then occurs is similar to diffusion, but with a small difference. Diffusion is the movement of particles of a substance from a high concentration to a low concentration. Osmosis is the movement of particles of a substance from a high concentration to a low concentration through a partially permeable membrane. In the case of a plant cell, this may mean that water would move into a plant cell if there was a higher concentration of water outside the cell than inside. However larger molecules either could not pass through or would pass thorough very slowly: Flow of water molecules The above diagram shows what might happen when the potato cylinder is put in to the Petri dish with distilled water in it. The water molecules are moving from the high concentration of them In this investigation we aim to investigate the factors affecting the rate of osmosis in a plant cell. ...read more.

Middle

In order to make the test as fair as possible, we will use a cylinder of metal which can be pushed into the potato and drawn out, bringing a cylinder of potato with it. These cylinders will be uniform in length and width and height, so the results obtained will be as accurate possible: Potato cylinder cylinder cutter Potato Several of these cylinders will be cut from the potato and put into Petri dishes containing different molarities of sucrose solution - distilled water, 0.2 mol, 0.4 mol, 0.6 mol and 0.8 mol of sucrose solution. The ends of skin must be cut off so the solution is allowed to enter all the cells and so they are the same length. Each cylinder shall be taken out and weighed every 5 minutes on electronic scales. Through weighing them as often as this, it will be possible to create an idea of the rate of osmosis. Because there will be solution on them when they are taken out, they will be rolled once forward on a piece of kitchen towel by the same person so that the solution on it does not affect the mass of it. ...read more.

Conclusion

and from the same potato. I would also dry each cylinder the same amount by rolling it the same length each time, using a new sheet of kitchen towel each time. If we were to further investigate rates of osmosis, we could see the effects of the other factors: pressure, heat and surface area (pressure would be too hard for us to carry out with the limited apparatus we have). To investigate heat, we could use the same concentration of solution each time, the same mass and surface area of potato cells, but each solution could be kept at a constant heat. We could place one experiment in a fridge, one at room temperature, and one could be kept on a low heat on a stove or other safe heating apparatus. Each experiment would have a thermometer with it to check the temperature. It would, however, be quite hard to measure rate of osmosis, especially in the case of the experiment in the fridge. To investigate surface area, we could cut potatoes so that they each had the same mass, but varying surface areas. Then the same method of finding rate would be used as done in the concentration experiment but the concentration would be uniform in all cases. ...read more.

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