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An Experiment to find the concentration of a potato cell cytoplasm compared to sucrose.

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Introduction

An Experiment to find the concentration of a potato cell cytoplasm compared to sucrose Aim: To find the concentration of a potato cell cytoplasm compared to sucrose. Prediction: I predict that as the sucrose solution's concentration increases, the potato cell will lose more weight. This is because of the osmosis of water particles from the potato cell cytoplasm to the solution, resulting in a loss of weight. As the concentration decreases, the potato will lose less weight until a certain point where the osmosis of particles in and out of the potato cells will be equal, the isotonic potential, showing the concentration of sucrose within the potato cell cytoplasm. I also predict the graph will have a negative correlation. Method: * Potato cylinders were gathered from the potatoes provided. * 6 pieces of potato of approximate equal size and mass were cut out. * They were dried by carefully rubbing them on tissue paper. * Each piece was assigned to a certain concentration of sucrose, and weighed on a digital scale. * The start weight was noted in the table. ...read more.

Middle

Therefore the particles in the water move due to osmosis into the potato cell, explaining the potatoes gaining of weight. The potato cell is hypertonic, meaning it has a higher concentration of solute. This is also evident on the second result but the change in weight has decreased, clearly because the concentration of sucrose in the beaker has increased, meaning there are less water particles in the beaker than distilled water. As we continue through the results, the potato cylinders begin to lose weight. I believe this shows that they have become hypotonic, meaning the cells have a lower concentration of the solute. This is at 0.4 Molar down to 1.0 Molar. This shows that in fact the potato cells are losing more water particles through osmosis, as there is a higher water concentration in the cytoplasm than in the 0.4 Molar sucrose. To fulfill the aim of the experiment, we must find the concentration of sucrose in the potato cell cytoplasm. To do this we must find the point where the two solutions are isotonic, meaning they are at a dynamic equilibrium. ...read more.

Conclusion

Another reason could be the error of cross-contamination of syringes, or a mistake in labeling, as all the solutions looked the same once in the test tubes. The scales were only to one decimal place and this could have proved decisive in the difference between percentage changes of weight in the potatoes. It was difficult to get the potatoes all the same size anyway, so we used percentage change to make the results more accurate. I feel that the experiment could have been improved if the problems mentioned were corrected. I also feel more of a variety of sucrose concentrations would be better in order to obtain more accurate and reliable results. To confirm the conclusion of the results, I feel that further investigations are needed. These could perhaps justify the conclusions made from the observations. There are numerous experiments that investigate the theory of osmosis that would be useful in supporting my results. We could in future look directly at osmosis in action through a microscope, and see the effects of plasmolysis and turgor in plant cells. It would be interesting to investigate the use of the partially permeable visking tube and the effects of osmosis, and perhaps also to observe not only the effect of osmosis and plasmolysis on the cell, but on the plant as a whole. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

*** This experiment lacked several sections that should be included in the planning. The candidate carried out the experiment and obtained sensible results but included no repeats or class data. This report needed more thought put into the discussion of results and the evaluation of the method.
Planning was not much in evidence. There was no trial experiment and no discussion of the key experimental variables. The prediction could be made clearer. If the prediction could be made quantitative ( perhaps by doing some background research) this would be helpful. A list of justified apparatus and chemicals and a risk assessment should be included.
Obtaining results: The student did not trial experiments but there was a good range of the independent variable recorded. This could be improved by including repeats or class data. The student should try to ensure all units and concentrations are clearly recorded in a table that has the independent variable in the first column.
Analysing Evidence and Evaluation: The graph was not available to view. The student needed to explain the extent to which the conclusion supported the prediction and look at ways of improving the reliability of the evidence in more depth.

Marked by teacher Stevie Fleming 29/05/2013

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