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Osmosis Investigation.

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Biology Coursework: Osmosis Investigation The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis, under different concentrations of sucrose. The cells chosen for study will be taken from potato strips as they provide a good supply of perfect plant material. Plant cells always have a strong cell wall surrounding them. When the take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. Turgid means swollen and hard. The pressure inside the cell rises; eventually the internal pressure of the cell is so high that no more water can enter the cell. This pressure works against osmosis, and this is why turgidity is very important to plants. When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become "flaccid." This is the exact opposite of "turgid". The contents of the potato cells shrink and pull away from the cell wall. Osmosis is when water passes from an area of high water concentration (a dilute solution) through a semi-permeable membrane to an area of low water concentration (a concentrated solution). ...read more.


I will avoid handling the broken glass. I will also wear safety glasses to avoid anything coming in contact with my eyes. I shall make sure that the surface and the space around me is dry and tidy before I carry out the experiment, as the water may affect the results and it will be easier to locate things when I need them. I will also check the floor if it is wet, to avoid any one slipping up whilst rushing about to get equipment (even though they should not be). From a similar experiment I have done previously I have learnt that just taking measurements of the potato cylinders is not accurate as the potato expands both lengthways and out wards during this process. Hence why this time I will be recording the mass, as opposed to the length. I will record the weight before and after the experiment to compare the increase or loss of mass. This will be more accurate. Also from similar experiments I have gained knowledge of different variables that affect experiments, and so the following will be taken into account; Solution volume - remember to fill beakers after sucrose is added. ...read more.


However if I was to repeat the experiment I would increase the time of the experiment to allow more osmosis to happen and possibly find out the saturation point of the potato tissue. The range of concentrations I chose, I believe to be adequate, but I would possibly create more concentrations, if I repeated the experiment, so that I would have more varied results, i.e. 5%, 15%, 25%, and so on. Also, I would try not to loose any water through evaporation or let any unwanted substances into the solution with the potato, next time, and so I would cover the opening of the beaker. There were not any out of the ordinary results, but some were not as close to the line as others. This may have been caused by human error. When the potato cylinders were removed from the beakers and dried I may well have dried some potatoes more thoroughly than others and so some would have more excess water, which would add to the mass. If the experiment was repeated and I could find another way to dry the potatoes that would ensure that all were dried in the same way for the same time, I would. However with all this said I think that the experiment was truly successful and I was very pleased with the complete comparison of my results with my initial prediction. ...read more.

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