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Investigating the effect of temperature on permeability of membranes

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Investigating the effect of temperature on permeability of membranes The investigation will look into the effect of temperature on membrane permeability using beetroot tissue. Background Cells of the beetroot contain a red dye called anthocyanin. Under normal conditions the dye is held within the cell by the cell membrane. However in an experiment to show the effect of various reagents (such as alcohol and detergent) on membrane permeability, the structure of the membrane is altered and the red dye leaks out of the cells. The reagents alter the phospholipid component of the membrane. Prior knowledge:- Plant cell walls contain cellulose. Cellulose is a polymer of beta glucose. Cellulose fibres have a high tensile strength; this helps the cell to withstand large pressures that develop within it as a result of osmosis. Without this the wall would burst when in a dilute solution. Cellulose fibres are freely permeable allowing water and solutes to reach the plasma membrane. Cytoplasm is an aqueous material varying from a fluid to a jelly like consistency. The cytoplasm contains proteins. Proteins are enzymes, which can be denatured by high temperatures. Most of the protein molecules in the cytoplasm float in the phospholipid layers. Some of the proteins are embedded in the outer layer; some in the inner layer and some span the whole membrane. ...read more.


In this case they are 20, 50 and 80 degrees Celsius. Place 5 centimetre cubes of water in the test tubes Place the beetroot tissue in the water bath. Make sure that the colorimeter reads 100% transmission when measuring water in a test tube. Take a reading after every 4 minutes. Take about 5 readings. My pilot study results were as following, Temperature degrees Celsius 20 50 80 4 minutes 50 65 25 8 minutes 50 10 1 12 minutes 60 8 0 16 minutes 80 25 0 20 minutes 75 18 0 Percentage transmission Changes to method after pilot study:- After doing my pilot study I realised a few mistakes n my experiment. The beetroot tissue size was too big to fit in the test tubes. For my final experiment I will change the size to about 0.5 centimetre cubed. The timing was too slow and there were some big changes in my results so I will reduce the timing to 1 minute after I take the result. There were some messed up results in my pilot study where the percentage transmission increased when it was supposed to be decreasing. I think this was due to the beetroot tissue still in the beaker when noting the result from the colorimeter. In my final experiment I will take the beetroot tissue out before taking the result. ...read more.


Safety goggles should be worn when handling hot water or anything else, which may get in contact with your eyes. Use tongs to carry test tubes placed in high temperatures. Precaution should be taken against splashing of water as it may be hot and could burn your skin. Fair test:- To make this experiment a fair test the size of the beetroot tissue must be the same and equal volumes of water should be added to each test tube. Take the readings on the colorimeter precisely after 2 minutes. Stir the anthocyanin solutions for exactly 5 seconds before putting them in the colorimeter. How results will be analysed:- My results would be recorded in a table with temperature against percentage transmission. The average will be taken of all the experiments and will be used as my final result to make it more precise. I will draw a line graph of my data. Variables:- The independent variable in my experiment is the temperature, which will be measured in degrees Celsius. The dependent variable in this experiment is the amount of red dye anthocyanin, which leaks out of the cell membrane. This will be measured in percentage transmission. Other variables, which may affect my experiment, are The stirring of the red dye before measuring the percentage transmission. The pressure will be kept constant (room temperature and pressure). The amount of water in the test tubes will also influence the results of my experiment and will be kept the same. Ehtisham kiani 01/05/2007 ...read more.

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