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Effect of Osmosis on Potato Cylinders.

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The write-up of my investigation. Aim: This experiment is to investigate osmosis on potato cylinders in different moles of sucrose solution ranging from distilled water to 1.0 mole in even steps. Prediction: Osmosis occurs when water is transported from a high concentration to a low concentration, through a partially permeable membrane. In this experiment we should find that the cylinders in the distilled water should become turgid because of water diffusing into the vacuole, making the cells increase in weight and length. The cylinders in the higher concentration of sucrose solution should loose weight and length and so become plasmolysed because of water diffusing out of the vacuole. This causes the cytoplasm to pull away from the cell wall and so making it flaccid. After collecting the data I would expect a graph to look like this. The distilled water would become turgid and the strongest molar solution would become plasmolysed. I would expect to find that the weight and the length would increase or decrease by the same amount for each cylinder and so they would either be the same curve or slightly off as shown in the graph opposite. Below is a diagram showing what happens when diffusion occurs across a partially permeable membrane. The membrane has small gaps, which a low small cells through, such as water and other molecules. Larger cells are not aloud through, these are molecules such as proteins, sucrose, and salt. ...read more.


5. The weighing scale was always put on zero at the beginning of each reading 6. Each experiment was conducted three times, just incase any readings were read incorrectly or a fault happened during the experiment. Safety: My group and I carried out several safety checks to make sure no harm could be inflicted on our selves or other members of our class: 1. Sharp objects such as the cork borer and knife were kept in the tray when not in use. 2. When cutting off the potatoes skin and boring holes, a board was used, it was not done in our hands 3. For obvious reasons, the potato and the sucrose solutions were not eaten or drunk. Method: For our first experiment, and for our second experiment, we started off as we had planned, leaving the cylinders in the solutions for 15 minutes. Unfortunately the results we obtained were not what we had expected and had hoped for. Instead of a dramatic change in the weights and length of our cylinders we had very little change and even the odd gain. So for our third experiment we changed our variables a little, making the waiting time 2 and 3/4 hours. We also increased the length and weight of our cylinders as we thought this too would improve our results, as there was more of a surface area for osmosis to occur. As we did not have enough time to re-repeat the experiment we stayed with the results we had and found the averages from the cylinders A, B and C. ...read more.


This is where the water concentration is equal to the external sucrose solution. Evaluation: Though I am fairly happy with my end results you can see from my graph that there are a few anomalous'. Using 0.6M of sucrose solution both the mass and the length dropped dramatically from the line of best fit. This could be because the petri dish was too close to heat or something may have gotten in to the solution besides the 0.6M of solution. This happens again at 1.0 M for the mass, but this time it increased dramatically. I would have expected it to have a decrease of about 45% but instead it had a decrease of 18%. This again could have been because of poor readings or because some thing else went wrong wen setting up the experiment. I f I could repeat this experiment I would still put the cylinders in their solutions longer and maybe increase their surface area. Also I would have a more of a vary on the sucrose solutions like having 0.1M, 0.3M, 0.5M, 0.7M, 0.9M and even others to find the exact osmolar concentration of the cells sap. This would make the results I obtained even more reliable. Other wise I think the method my group and I used was good, and successful. The results were also reliable, even though I could get yet more reliable results, as I have explained above, for the experiment I carried out. Osmosis on Potato Cylinders. Kathryn Hinchcliffe. ...read more.

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