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An investigation into the effect of temperature on the permeability of cell membranes

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An investigation into the effect of temperature on the permeability of cell membranes Introduction All plant cells have a cell membrane, as shown in the simple diagram of a plant cell below: Plasma membranes have an external layer of proteins that hold the lipid molecules in a fairly rigid arrangement. Protein lined pores account for the most part of the cells permeability. This structure of a cell membrane is showed below: The cell (plasma) membrane is very important, it controls what enters and exits the cell. It acts as a selective barrier between the internal and external fluid. This process supplies the cell with raw materials and removes waste products. Normally, this done by diffusion. Diffusion is based on differences in concentration. It spreads the substances from high concentration to low concentration. Various things can diffuse through the membrane for example, oxygen, carbon dioxide, ions and water molecules (through osmosis). The molecules move in a random motion, which leads to the equilibrium of each concentration. Some of the membrane is permanently open whereas others open and close, for example those that control the intake of ions. The rate of diffusion is dependent on the surface area. The cell membrane also uses the process o active transport, which requires proteins with the aid of cell energy. ...read more.


I will also measure the temperature and pH of the water to ensure that the variables are kept constant and it is a fair test. I will prepare the water baths, keeping them at a constant temperature top insure the accuracy of the experiment. There will be six water baths of different temperatures, fifty Degrees Celsius, fifty-five Degrees Celsius, sixty Degrees Celsius, sixty-five Degrees Celsius, seventy Degrees Celsius and eighty Degrees Celsius. To avoid the temperature of the water baths falling I will place tin foil over them to keep the heat in. I will slice all the beetroot and place them onto the mounted needle. When slicing the beetroot I will ensure that each slice is exactly the same so that there is no increase in surface area as that could alter the experiment. To do this I will use a cork borer to cut the diameter of the cylinders, and a ruler and scalpel to cut the width, which will be about three millimeters thick. I will then place these discs (thirty altogether) into a petri dish full of water, wash them and then leave them for about five minutes. This is because when the beetroot is cut, it will cut through cell membranes, this will mean the contents of the cell will leak out. ...read more.


They give a clear idea of effect of temperature on the permeability of the plasma membrane, which I believe to be a productive experiment. If I were to repeat this experiment I would cut out some of the errors that were made to make it more accurate. Some of which were human errors, for instance in timing the amount of time in the water bath, the amount of water in the test tubes possibly diluting the pigment in the vial, and also reading the colorimeter accurately. Additionally, the test tubes were not all left to stand for exactly the same amount of time, as the ones I did first would stand for longer while I was doing the others, this also may have affected the dilution of the pigment. To further this experiment I would investigate the permeability of plant cells beside beetroot, and perhaps also some animals' cells, and see if the effect on the permeability differs. I could also do the experiment using different variables and see what affect they have. Equipment list o Thirty slices of beetroot o Six test tubes each containing six milliliters of water o A test tube rack o Six water baths ranging from fifty to eighty Degrees Celsius o A mounting needle o A scalpel o A colorimeter o A petri disc o Six vials o A timer ...read more.

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