Biology Coursework: Osmosis Investigation - page 5
Keywords: biology coursework osmosis potato potatoes sucrose molar mass change
By ruth on 08/11/2006 17:19:48
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 5 of 7 pages: 1 2 3 4 5 6 7
my prediction however I was not sure of the exact concentration and now I have a better estimate, but the general trend is the same. The general trend being, as seen on the graph, that the higher the concentration of sucrose the more weight lost by the potato. This is because of osmosis, where a partially permeable membrane is between two solutions and the water molecules move from the region of higher water potential to a region of lower water potential. The partially permeable membrane only lets through small particles such as water molecules, and larger ones such as sugars can not move through these. So when the concentration of the solution was lower than the potato’s the water diffused from the concentration into the potato, therefore the potato gained mass. The potato cell starts to lose water through plasmolysis when the concentration around it has a higher concentration of sucrose than inside the potato cell. So this causes the water to diffuse out and so the cell becomes flaccid. This meaning as the water has been drawn out and so the cytoplasm shrinks and becomes flabby, and the cell is now plasmolysed. The opposite happens when water enters the potato cell, it swells up to become turgid.
I can see on the graph that the line seems to be curving towards a straight line. This means that the water can only be drawn out of the potato cell to a certain point, and will not continue happening until there is no potato mass. This is because the potato is not purely made up of water and even if all the water is it has diffused out into the solution there are other components of the potato which will account for its mass.
The graph of my results has the same trend as the graph in my prediction but it is slightly more of an accurate curve as the line of best fit has more point to go around. The only difference with my prediction and conclusion is that I estimated the concentration of the potato to be about 0.5 molar, when it was in fact 0.4 molar.
Evaluation:
From the graph it can be seen that at the end the line of best fit goes through two points, I thought that maybe one of these was an anomaly but I wasn’t sure which
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