Aim: To investigate how effect of Detergent Concentration (cont.) has on Membrane permeability of Beetroot cells.
Hypothesis: I predict that as detergent concentration increases, the solution will become less clear, plus mass increases. The increases in mass will indicate that the water potential of the Beetroot cell is lower than that of the surrounding sucrose solution. The Beetroot discs will become flaccid and decrease in mass if the water potential of the surrounding solution is lower than the water potential inside the beetroot cell. I predict that Osmosis will not occur (at 0% cont.) if the water potential of the sucrose solution (detergent) and the water potential of the cell’s cytoplasm are equal. I also predict that an increase in detergent concentration will lead to more damage to the cell membranes, decreasing their permeability, and therefore allowing more of the pigment to be released. I predict that if the concentration of detergent is doubled, double the cells will be (at least partly) damaged, which will lead to double the amount of beta cyanine being let out of the cells.
Control Variables: In order to make the test fair, only one person must time the amount of time the beetroot has been inside the concentrated detergent and the distilled water, to make the test more accurate because different people have different reaction times, so by using the same person to time the amount of time the beetroot has been inside the concentrated detergent and the distilled water, the reaction time is not change. The same person should always cut the beetroot because different people have different eye quality, so by using the same person to cut the beetroot will result to a fair test, also when cutting to be sure to use the same ruler and making sure the cutting devices that is being use is washed before cutting the next 1 out of 4,1cm length beetroot. The beetroot should always be washed to remove the pigment leaked from damaged cells. Each test tube should contain the same amount of distilled water (3/4), and each boiling tube should contain the same amount of concentrated detergent, making the test fair. Also all tests should be hailed in the same part of the room because temperature may varies because windows may be open or it may be done near the heater, this could damage the results, because a higher temperature could mean the membrane is broken due to the heat, and not solely the detergent, An increase in temperature will also damage and denature the plasma membrane and cause the cytoplasm and other substances contained within the membrane to leak out, so to maintain a good result test should be done in the same places. The same size discs of beetroot must be used throughout, otherwise larger pieces would leak more beta cyanine and make a given detergent concentration have a higher colour intensity, in comparison to the other detergent concentrations. This would affect the accuracy of the results, as a smaller volume of higher colour intensity would be needed to make it the same as that of the standard, making the test fair.
Table of Absorbance values measured at increasing Detergent
Detergent Concentration (%)
Mean of Absorbance to 2 d.p.
Table of Colorimeter values measured at increasing Detergent concentrations:
Detergent Concentration (%)
Mean of Colorimeter values to 2 d.p.
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