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Experiment to show the effect of Temperature on membrane permeability In beetroot

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Experiment to show the effect of Temperature on membrane permeability In beetroot Joseph Colledge Introduction Plants are unique among the eukaryotic organisms whose cells have membrane enclosed nuclei and organelles, because they can manufacture their own food. Chlorophyll, which gives plants their green colour, enables them to use sunlight to convert water and carbon dioxide into sugars and carbohydrates, chemicals the cell uses for fuel. Like the fungi, another kingdom of eukaryotes, plant cells have retained the protective cell wall structure of their prokaryotic ancestors. The basic plant cell shares a similar construction with the typical eukaryote cell, but does not have centrioles, lysosomes, intermediate filaments, cilia, or flagella, as does the animal cell. (Reed 1998) Plant cells do, however, have a number of other specialized structures, including a rigid cell wall, central vacuole, plasmodesmata, and chloroplasts. In prokaryotes and plants, the plasma membrane is an inner layer of protection since a rigid cell wall forms the outside boundary for their cells. The cell wall has pores that allow materials to enter and leave the cell, but they are not very selective about what passes through. The plasma membrane, which lines the cell wall, provides the final filter between the cell interior and the environment. Lipids and proteins are the staple ingredients of membranes, and, the most abundant lipids in membranes are phospholipids. ...read more.


Method Apparatus Test tubes Test tube rack Cork borer Tile Scalpel Small beaker Graduated beaker Large beaker Thermometers Water baths 1. Use a cork borer to cut cylinders of fresh beetroot tissue. Then place onto a tile and cut into 60, 2mm wide discs. 2. Place all discs in a small beaker and wash under a running tap for at least 5 minutes until no more pigment is released from the damaged cells. 3. Label test tubes 30�C, 40�C, 50�C, 60�C, 70�C and 80�C 4. Use a graduated pipette to add 20cm� cold water to each of the test tubes. 5. Add labelled test tubes to water baths using a large beaker, tripod and gauze and for any temperatures which aren't provided use a Bunsen burner. 6. Add 10 discs to the test tube and leave and leave in the water bath for 10 minutes. You should see pigment leave the tissue. 7. Remove the test tube from the water bath and carefully decant the liquid into a fresh test tube, leaving the discs behind. 8. Repeat the procedure for the other tubes. Shake the tubes, hold to the light and compare the colour of the liquids in each. 9. With a blue filtered colorimeter place a selection of each test tube in turn and compare the colours of the liquids. ...read more.


There might be a higher controlled permeability for such compounds that are supposed to enter through the membrane but it will not break down, releasing the red beet colour. When the temperature goes beyond these limits water expands, putting pressure on the membranes from within. The lipid part of the membrane liquefies, making it more prone to leakage. The proteins that span the membrane fall apart, creating holes in the fabric. All this combined will allow compounds to exit the cell. The reason this is possible is physics. Higher temperature makes all molecules shake and vibrate more. The faster movement disrupts any ordered structure there might have been, eventually destroying the structure altogether. Another reason for release of the pigment is due to basic osmosis, in that the interior of the cell has a much lower water potential than the outside of the cell so that when there is an increase in the temperature it in turn causes the water to go from the higher concentration to the lower concentration (a typical gradient) The causes the release of the pigment as the walls are literally broken down due to pressures put against them and thereby causing the pigment to be diffused into the surrounding water. To conclude, the hypothesis stated in the introduction did indeed concur with the results found, in that an increase in temperature increased the amount of pigment released. ...read more.

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