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

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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.
  •  The pieces were placed in a 10ml capacity, in a test tube, of a variety of concentrations of sucrose (weakest to strongest: distilled water, 0.2 Molar sucrose, 0.4 M, 0.6 M, 0.8 M, 1.0 M).
  • The test tubes were placed on a rack and we started the stopwatch.
  • After 25 minutes, we stopped the timer and the pieces were taken out of their test tubes and dried.
  • The final weight of each piece was again measured, and a percent change was calculated to increase the accuracy.
  • These results were noted on the table and a graph was created.
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Results Table:

Analysis of results: The graph shows a strong negative correlation, as was predicted. As the concentration of the sucrose increased, the mass of the potato decreased. When the potato cylinder was placed in the distilled water, it gained 0.2g in weight. This confirms the scientific idea of osmosis. Osmosis is when water particles move through a semi-permeable membrane from an area of high concentration (of water particles) to a lower one. This is a very common occurrence in cells where water moves in and out of the cell membrane. This is similar to diffusion, but instead ...

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*** 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.