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When you submerge a plant cell in water, water flows through the cell wall and cell surface area into the vacuole from the outside. As a result, the cell swells up, but does not burst. This is because the cell wall stops the cell expanding too much.

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Introduction

Introduction When you submerge a plant cell in water, water flows through the cell wall and cell surface area into the vacuole from the outside. As a result, the cell swells up, but does not burst. This is because the cell wall stops the cell expanding too much. When this point is reached we say that the cell is fully turgid. This type of diffusion is called osmosis, and takes place through a partially permeable membrane. The water moves from a dilute solution to a concentrated solution. This stops when the levels of water in each solution are equal. The experiment we are about to do will prove that osmosis takes place, and that it takes place in a living cell. We will then attempt to find out the percentage of sugar within a potato. Preliminary Experiments Viskin tubing is a special kind of membrane, as it has millions of tiny holes in it. The experiment that we are going to do will show how a special kind of diffusion, called osmosis occurs through a membrane that lets small molecules through but not large molecules. This type of membrane is known as a semi permeable membrane, or a partially permeable membrane. The following experiment will show that osmosis takes place. ...read more.

Middle

Another example is in the 5, 10 and 10 percentage solutions. Each repeat experiment should have increased, however they did not, they all decreased. Evaluation The experiment may not have worked for the following reasons: The carrots we used had just been removed from a fridge. This may have damaged the cells in the carrots, preventing osmosis from taking place. Carrots are also root vegetables, which contain cellulose, which might have hardened preventing the exchange of water. To improve the experiment we are going to use potatoes instead of carrots. We will also use sucrose, a sugar solution, instead of salt. The range of percentages we will use will also change. The new percentages will be: 0%, 10%, 20%, 30%and 40%. Finally we will change the length of time. This is because if we leave the potato for a long period of time the cells may die, and osmosis will stop. Potatoes Prediction I think that the potato will contain about 18% sugar. I know that a potato contains a certain percentage of sugar, however I don't know the exact percentage. To find this out I will place potato pieces into different sugar solutions. These are: 0%,10%, 20%, 30% and 40%. I will know what the percentage of sugar in the potato is, when there is no loss or gain in weight in the potato that is the amount of sugar inside it. ...read more.

Conclusion

The results were: % Potato 1 (g) Potato 2 (g) Potato 3 (g) AV (g) Potato 1 (g) Potato 2 (g) Potato 3 (g) AV (g) Weight Gain or Loss 12.5 1.70 1.74 1.64 1.70 1.64 1.70 1.62 1.65 -0.05 15 1.68 1.53 1.73 1.65 1.57 1.44 1.62 1.54 -0.11 17.5 1.71 1.72 1.93 1.79 1.51 1.50 1.75 1.59 -0.10 These results show us that the amount of sugar in the potato is between 10% and 12.5%. This is because at 12.5%, the potato loses weight, meaning that there is less sugar in the water surrounding it than in the potato. Graph showing the increase and decrease in weight of potatoes. Conclusion Our experiment was a success. We know this because for the experiment to be successful, all three potatoes in each sugar solution would have all either have to increase or decrease. This is what happened in our experiment. I have reached a conclusion that the amount of sugar in a potato is just over 10%, at about 12%. I reached this conclusion because I have drawn a line of best fit on my graph which contains the results from the experiment, and where the line reaches the x axes, that is the percentage of sugar in the potato. Evaluation To improve our experiment next time we could use a larger amount of potatoes. We could also use a broader range of sucrose solutions to make our results more accurate. 1 ...read more.

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