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The effect of temperature on Membrane Permeability

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The effect of temperature on Membrane Permeability It is my aim to investigate whether or not temperature, or more specifically heat, affects the permeability of a cell membrane. Background Based on the fluid mosaic theory we believe the plasma membrane is composed of a phospholipid bilayer about 7-10 nm thick. This theory also suggests that proteins in bedded in the membrane are used for transporting substances across the membrane, creating pores for substances to pass through and act as carriers. Method i. The beetroot must be cut into cylinders and also washed as to remove any anthocyanin pigment that has leaked out the cells because of the cutting, then placed in distilled water ii. Heat 200cm3 of distilled water to 85oC in a sensible sized beaker iii. Whilst the water is heating, use a syringe to place 10cm3 of distilled water into each of ten test tubes. Label the tubes 85,80,75,70,65,63,60,55,50,45 (as these will be the temperatures used) iv. Cut 10 of the cylinder beetroot pieces into lengths of 5cm v. ...read more.


Results Temp (oC) Percent of light absorbed 85 95 80 92 75 93 70 75 65 17 63 9 60 24 55 11 50 4 45 15 We can see form this table that the percent of light absorbed decreases as the temperature the beetroot was subject to, also decreases. In other words, as the temperature increases, more of the red pigment was able to leave the cell into the distilled water and so the more pigment there was the more light would be absorbed. The above graph clearly shows that the amount of pigment released peaks at 700C, so we can say that at this point the membrane of the beetroot cell becomes severely damaged and a lot of the red pigment that is usually stored in the vacuole of the cell is no longer bound by the internal membrane surrounding the vacuole or the outer membrane. The graph also shows that at 60oC and 45oC the amount of pigment released also increases, however I do not believe that this is a usual occurrence and is an anomalous result. ...read more.


I also think that a different beaker of heated water should be used for each beetroot cylinder, as I found that much of the red pigment was escaping from the cylinder while still being heated, this could effect the results in the way that for the higher temperatures a lot of the pigment has already leaked out, and also that the red pigment in the water may attach to the beetroot cylinders used in the cooler temperatures test, for example at 80oC a lot of the red pigment leaked out of the cell, this would therefore give a lower light absorption rate and give the 50oC cylinder a higher absorption rate as the pigment may have attached to the cylinder while being heated. If I had more time I would like to repeat the experiment three times and gather three sets of results for each temperature and then use the arithmetical mean average. I would also like to test other types of cells using a similar method to examine if temperature effected these in the same way as the beetroot cells. Steven Spencer ...read more.

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