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An experiment to determine the osmotic values ofChinese radish and Potato cores.

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An experiment to determine the osmotic values of Chinese radish and Potato cores. Osmosis is the movement of water from an area of high water potential (?) to an area of low water potential through a selectively permeable membrane. The diagrams above shows that only the water molecules can move quickly through the pores in the selectively permeable membrane. The sugar molecules (glucose arde too big to move through the gaps withease. Since there is a higher water potential on the left-hand side more water molecules will move from right to left, than from left to right. What happens if a cell is placed in pure Water H20: If a plant cell is placed in pure water, water outside the cell will flow into the cell by osmosis as the interior of the cell has a lower water potential than the pure water. The reason why the interior has a lower water potential is because the cytoplasm has substance like glucose dissolved into it. As more and more water flows into the cell the cell becomes more and more rigid. Eventually the cell becomes turgid and this is when the cell will not accept anymore water as the water potential inside and outside now balanced. If we replicated this with an animal cell it would burst as water would enter osmotically and then the cell would become rigid and there would be no support from a cell wall, and thus the cell will burst. What happens to a plant cell in 1.0M Glucose Solution: Loss of water by Osmosis Shrinkage of Cytoplasm Membrane being pulled away from the cell wall In the conditions of 1.0M Glucose solution the cell will tend to lose water as it has a higher water potential than the outside medium, Water leaves the cell via osmosis and the cell become less rigid in other words flaccid. ...read more.


As I predicted all the Potato cores in glucose solutions with a molarity higher than 0.3+M lost mass this is due to the fact of osmosis, thus the cores have a molarity of 0.3M. This is so because all the cores in solution 0.3+M lost mass as the cores had a higher water potential than the outside solution, and due to osmosis water molecules would move out of the cores. And all the cores in solutions lower than 0.3M gained mass as this time then cores had a lower water potential than the solution outside. The evidence also shows that the cores tend to lose an extra 7% of their mass every time the molarity of the solution goes up by 0.1M. My predictions for the 0.0M solution was reasonably accurate as I predicted a significant gain in mass at approximately +15% and the mean change was 12.6% this is very close to my actual predictions as it was only 2.4% away. So I am happy about this prediction. For the 0.2M solution I predicted a slight increase at approximately +5% and the actual percentage change was +5.2% so this was very accurate. For the 0.3M solution I predicted 'par' results at 0% and I wasn't too far off with the result being at 0.4%. For the 0.4M solution I had expected a -5% change in mass and like the 0.0M solution I was a little bit off with the prediction, this could be due to the fact that these predictions were made with the help of a prep-experiment, and the readings could have been a little bit off. For the 0.6M solution I had expected a sharper drop in mass at -15% but the final result was -18.4% so I was a quite a bit off. ...read more.


I would also test from 0.0 right through to 1.0 and all the intermediate stages, i.e. 0.0M, 0.1M, 0.2M etc. this would enable a more accurate 'line of best fit' and a better understanding of the 'performance' of the cores through the intermediate stages. I would also have the cores cut from the same vegetable, as there is the possibility of there being so many cores to supply one persons set of cores may have come from 2 different sources which could mean an unfair result, as one may have been harvested longer than the other one. I would also like to have the cores cut by myself, freshly, as undoubtedly the cores will have been pre-cut and this would mean that the cores could have lost moisture which could have affected the results if the cores had been freshly cut. I reliability of the results obtained by through the experiment on the whole were very reliable and they are more than enough to support the conclusion even with the anomalies as we can tell by the graphs where the points should have been. Looking at these results as well as the prep results I believe they are a fair reflection of the predictions and the aim. To further prove this conclusion I would repeat this experiment several times, but at spaced out intervals just in case the outside humidity or tiredness make would make human error more of a chance. I would also make sure that the 'freshness' of the materials used were the same. The extra experiments would be carried out with amendments stated above. But I honestly believe that this was a very fair and accurate experiment so I am happy with the results. Although any extra experiments would iron the last few small creases and cement my conclusion together. ...read more.

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