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Osmosis in Potato Cells

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Introduction

Candidate No. 9115 Biology Investigation Lee Ramsingh Centre No. 51411 Osmosis in Potato Cells Purpose of investigation We will investigate OSMOSIS in potato cells. From this, we will analyse the turning point, where the concentration of the sucrose solution is approximately equal to the concentration of sucrose inside the potato cells. Initial Notes We have decided to use the concentration of the sucrose solution as our variable. A range of 5 different concentrations should be sufficient, and 5 repeats will be enough to give us a good average in the time allocated. Sucrose is chosen instead of glucose, because glucose molecules are smaller than sucrose molecules and is similar to water molecules. We will be given a potato and 1.0 molar sucrose solution. The different concentrations will be: 0.1, 0.2, 0.3 0.4 and 0.5 molar solution. We will have to make these different gradients by mixing the solution with water in proportion. Therefore, a 0.2 molar solution will be 1 part sugar solution and 4 parts water. Using evidence from our previous experiment, we know that the turning point will be between 0.5 mol and 0.1 mol. We know also from our previous experiments that 30 minutes will be the optimum amount of time required for the experiment to get the best results. See Preliminary Work. We will keep all the potato strips the same length of 50 mm. ...read more.

Middle

We also know that water will cause the mass of the potato chip to increase, whilst a sugar solution of 1.0 will cause the mass of the potato chip to decrease. Since the mass change went from negative to positive between 0.5 mol solution and 0.1 mol solution, we can determine that the solution of the sugar inside the potato cells is between 0.5 mol and 0.1 mol. The next experiment will study the range in smaller increments, thus greater accuracy. Aim: This is the final work to determine the solution strength of the potato cells. Variables: Concentration of sugar solution Constants: Size of potato chips Amount of time for each chip Temperature of the solutions (hotter molecules will move faster) Standard Atmospheric air pressure Type of potato used * The whole potato chip must be completely immersed in the sugar solution Equipment: 5 Test Tubes (each solution and repeat will use the same test tube for economical purposes) 1.0 molar sucrose solution 1 Core borer No. 2 size 1 Water bath (to keep temperatures constant) 1 Potato 1 Glass beaker (to mix together sucrose and water) 1 Measuring cylinder (for accurate readings) 1 core-borer 1 knife Digital balance Filter/Blotting paper Method: 1. Prepare the solutions by diluting the 1 mol. Solution with the correct amount of water using a measuring cylinder. For example: The 0.3 mol solution will use 3 cc of 1.0 mol solution and 7 cc of distilled water for a total of 10cc. ...read more.

Conclusion

Thus, they absorbed water and increased in mass and turgor pressure the cells become turgid. However, when they were placed in a solution with less water, they needed to lose water to equalise the concentration in the cells with the concentration of the solution. Thus, the vacuole shrunk in size (contains water) and there was less water in the cytoplasm, causing the cell membrane to decrease in size. Because the cell wall stays fairly rigid, the cell becomes limp and flaccid. The cell is kwon to be plasmolysed and they decreased in mass. Equal concentrations are impossible to achieve, though. This is due to the fact that the concentration of sugar and water must be equal. However, sugar molecules are too big to fit through the cell membrane, so the sugar levels remain different. Only the water content can change. With OSMOSIS in general, however, when the concentrations are equal on either side of a membrane, it is known as 'isotonic'. The skin of the potato was not used, as it contains different cells along with impurities, which would affect the outcome of the experiment. Evaluation I believe that the experiments went very well, although the results did vary more than I expected. It could be due to the potato chips having extra cells, or dead/inactive ones. However, I managed to get a smooth curve on the graph. We could now investigate the rate of OSMOSIS, more accurate attempts at the solution strength, different types of vegetables, and the optimal temperature for OSMOSIS. ?? ?? ?? ?? ...read more.

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