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An Investigation to find out how different strengths of salt solution affect potato cells through osmosis.

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Introduction

Biology Coursework 2003 An Investigation to find out how different strengths of salt solution affect potato cells through osmosis. Aim I aim to investigate the effect of different concentrations of salt solution on potato cells when osmosis occurs. Introduction I intent to set up this experiment using equally sized cylinders of potato submerged in salt solutions of different concentrations. I will then observe the percentage change in mass over a set period of time. This will show me how much osmosis has occurred. Scientific Theory of Osmosis Osmosis is defined as the solvent of any solution being able to pass through any semi-permeable membrane from a region of high concentration to a region of low concentration until both solutions reach a state of equilibrium. This means that water can flow through a porous material, such as a cell wall or visking tubing, in order to balance the levels of concentration. The molecules are then randomly distributed throughout the solution. Water particles are small and can therefore easily fit through the material; however, larger particles such as salt or glucose are too big to fit through the material. Osmosis has a significant effect on living cells. Animals cells will burst in pure water because, as the cytoplasm is fairly concentrated, the water, which is less concentrated, will enter the cell. ...read more.

Middle

I prepared 15cm of each strength. To make 0M, I will use 0cm 1.0M and 15cm H O. To make 0.2M, I will use 3cm 1.0M and 12cm H O. To make 0.4M, I will use 6cm 1.0M and 9cm H O. To make 0.6M, I will use 9cm 1.0M and 6cm H O. To make 0.8M, I will use 12cm 1.0M and 3cm H O. I will measure these using a 15cm syringe each time and will measure it directly into the beaker. 4. I must then label each beaker so as to avoid confusion. 5. I will then measure each potato cylinder and then place a coloured pin in it, recording the information carefully in the table shown below. 6. I then will place the cylinders in the beakers and begin timing. 7. While waiting I will tidy up and prepare labeled filter paper to set the cylinder on when I remove them. 8. After 3 hours, I drained out the solutions and placed the cylinders on the filter paper to remove any excess solution, being careful to put the correct cylinders on the matching filter paper to avoid confusion. If the excess solution is not removed, it may affect the results depending on the amount of excess solution. 9. I will remove the coloured pins and re-weigh each cylinder and record the results. ...read more.

Conclusion

I could also increase the number of different concentrations which would give me a vast variety of results. This would allow me to find the isotonic point much more accurately than what I estimated, which was very approximate. I would also cut the potato cylinders more accurately because although I was recording the mass, the surface area still plays an important part in keeping the test fair. The potato cylinders should be of equal weigh, size and shape. As well as the potato, the solutions could be measured more accurately by perhaps using a burette to determine the molar concentrations. This would ensure an accurate amount of liquid in each beaker. I could also weigh the cylinders on a more accurate scale, for instance 0.0000g rather than 0.00g. I could perhaps find a more accurate way of removing the excess liquid from the potatoes after the experiment which is more accurate. Also, I did not have time to repeat the experiment a second time. This would be a good idea if I were to do the experiment again. Only one of my results seemed to be slightly inaccurate. This could have been because of a number of reasons. Maybe I didn't cut the cylinders equally or the solution was inaccurate. Perhaps I did not dry it as thoroughly as the other, which would have added to the mass. With all this said I think my experiment went very well and I am pleased with the outcome. Jennifer Humphrey ...read more.

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