Beetroot Practical 2. 8 An investigation to find out whether the raise of temperature will increase the permeability of the cell membrane: The question being answered from doing this experiment is ‘How do different temperatures affect the permeability of the plasma membrane of beetroot? ’ Beetroot contains red pigments called betalains, located within the cell vacuole. Normally the pigments cannot pass through membranes but they leak out when the beetroot is cooked or placed in alcohol. The aim of this practical is to use beetroot to examine the effect of temperature on cell membranes and relate the effects observed to membrane structure.
To function correctly a cell needs to be able to control transport across the partially permeable membrane. I believe that with the increase of temperature applied onto the plasma membrane, the structure of the membrane will become damaged and the intrinsic and extrinsic proteins in it will eventually denature causing the pigment within the vacuole of the beetroot to leak out. Method List of equipment and apparatus used in this experiment: ? Colorimeter ? Thermometers ? Water baths at various temperatures ? Stopclock ? Test tubes ? Small measuring cylinders ? Cuvettes ? Cork borer Mounted needles ? Beaker about 250 cm? ? Blue Filter The dependent variable was the absorbance. We measured it by using a colorimeter which compares the amount of light getting through a solution with the amount which can get through a sample of pure solvent. It was controlled by filling the test tubes with distilled water. The independent variable was the temperature of the water. We controlled it by using a water bath which contains a thermostat that regulates the temperature and keeps it constant. Instructions: 1. Use a cork borer to cut some beetroot tissue into discs about 3 mm thick. 2.
Place the already cut discs of beetroot into a beaker and wash them in cold water for at least 5 minutes to wash away excess dye. 3. When the beetroot discs have been washed impale about 6 of them on a mounted needle 4. Place them into the test tubes containing distilled water 5. Incubate the test tubes in water baths at fixed temperatures 6. Use a stopclock to time 5 minutes for each test tube 7. Remove beetroot sections using a technique that does not squeeze the slice. Shake the water solution to disperse the dye 8. Switch on the colorimeter and set it to read % absorbance 9.
Set the filter dial to the blue/green filter 10. Using a pipette accurately measure 2 cm? of distilled water into a cuvette. Place the cuvette into the colorimeter and make sure that the line is shining through the smooth sides. 11. Adjust the colorimeter to read 0 absorbance for clear water. 12. Take the reading for absorbency. 13. The same method has to be repeated for all the different temperatures. Any possible risks and errors that could have affected the results: • The discs might have been from different beetroot tissue of different age – random • Measurement errors – systematic The time the beetroot discs were in the water before placing them into the water bath – systematic Results |Temperature |Absorbance (%) | |? C | | | |1 |2 |3 |Average | | 0 |0. 18 |0. 22 |0. 16 |0. 9 | |20 |0. 26 |0. 24 |0. 33 |0. 28 | |40 |0. 31 |0. 38 |0. 35 |0. 35 | |60 |0. 46 |0. 45 |0. 46 |0. 46 | |80 |1. 24 |1. 10 |1. 35 |1. 23 |