Investigating the effect of temperature on plant cell membranes
The purpose of this activity is:
• to practise experimental and investigative skills
• to investigate the effect of temperature on cell membrane structures
SAFETY: Always carry scalpels clasped to a tile and with the tip pointing away from you.
Beetroot cells contain pigments called betalains that give the tissue its dark purple-red colour. The pigment is contained in the cell vacuole.
a. Collect 3 or 4 beetroot cores from the beaker provided. Cut each core into 2 cm sections until you have enough for one core for each temperature of water bath that you will be using. Put your 2 cm sections into a test tube with plenty of distilled water. b. Label a set of test tubes (one for each temperature of water bath) with the temperature and your initials. Add exactly 5 cm3 of distilled water to each test tube and place your tubes, one in each water bath, for 5 minutes to equilibrate to the temperature of the water bath. c. Remove your beetroot cores from the distilled water and blot gently on a paper towel. Decide whether forceps or mounted needles are best for handling the tissue and what damage this might cause to the cores. d. Place one 2 cm beetroot core into each of your test tubes and leave in the water bath for 30 minutes. e. After 30 minutes, shake the test tubes gently to make sure any pigment is well-mixed into the water, then remove the beetroot cores. f. Describe the depth of colour in each test tube. A piece of white card behind the tubes will make this easier to see. Arrange the tubes in order of temperature of the water bath. Describe any relationship between the amount of pigment released from the beetroot and the temperature. g. If you have access to a colorimeter, set it to respond to a blue/ green filter (or wavelength of 530 nm) and note whether you are measuring absorbance or transmission. Check the colorimeter reading for distilled water....
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