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An Investigation into Potato Tissue

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Introduction

An Investigation into Potato Tissue Aim: To investigate how varying the sucrose concentration around piece of potato tissue affects the diffusion of water (osmosis) into or out of the cell. Introduction: Definition of Osmosis: This is the diffusion of water molecules from an area of high water concentration (dilute solution) to an area of low water concentration (concentrated solution) through a permeable membrane. The rate, again, depends on the surface area, the concentration gradient and the properties of the partially permeable membrane. A diagram of Osmosis: We have looked into osmosis previously in the experiment of turgid and plasmolysed onion cells, and a visking tube. Demonstration of Osmosis Using a Visking Experiment The Visking tube experiment was used to demonstrate osmosis. The Visking tubing was semi-permeable, which allows small molecules (water) to pass through, but it doesn't allow the larger ones (sugar). Apparatus * a small length of capillary tubing * a larger amount of Visking tubing * 0.5 sucrose solution * pipette Osmosis Experiments Factors that will affect the rate of osmosis will be the Independent variables, the dependent variables and the external variables. Independent variable = Concentration of sucrose solution - If the sucrose solution is changed, osmosis will change in rate and direction. Dependent variables = Change in mass of potato. ...read more.

Middle

Making it plasmoylised and decrease In both weight and length. Evaluation From this experiment I understood osmosis, a lot better. I thought though for my final experiment that I should make some changes to the variables to make it a fairer test. For example in this experiment I left them for 30minutes. I got pretty good results but I think that I possibly could get better. So in my final experiment think that I might leave them for longer maybe around an hour to give osmosis more of a chance to happen. I think that this experiment was accurate but for my final experiment I would like to improve it. I am quite confident with my conclusion as I think that it makes sense. If I was to look further into osmosis I think that I might do the same experiment a lot more, and in different paces as well, to see if the temperature varies. Weather osmosis works better in hot conditions rather then cold ones. In my next experiment again to keep it precise I think I might use an electronic balance that measures to 0.01(g). Making sure that the electronic balance is put back to zero each time. I also think that to be sure that my final experiment, my results are reliable Ill do it twice with two of each sucrose solution. ...read more.

Conclusion

If I had to do this experiment in more detail, again I think that I would do the same concentration of sucrose solutions as I think that they are a good range. I think that if I could change the experiment, I would do lots of the same solution, putting each of them in different spaces. For example, one outside, one inside, too see if osmosis worked well in hotter or colder temperatures. I did check the temperature in my experiment but the temperatures were extremely constant. This was good for my experiment as I wanted a fair test. Extremely different temperatures in my experiment would have maybe made the osmosis in one test tube work better then in another. I would have also left some for longer and some for shorter periods of time, as in my two experiments I found that half an hour wasn't long enough for osmosis to properly and I don't know what the right time period in a further investigation I would try and find this out. The last thing that I think that I would of done if given a longer amount of time and more resources would have been maybe to add a colour die to the water and sucrose solution to see if a could actually watch osmosis happen. ?? ?? ?? ?? Kelly Biology coursework ...read more.

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