Beetroot contains betalain pigments within it’s vacuole, which gives it it’s purple-red colour, it’s this pigment which leaks out as the beetroot is heated and the cells membrane begins to break down. The practicals aim is to show the effect of temperature on the cell membrane by observing the colour change of the water the beetroot was placed in. The cell membrane is important as it controls the substances enters and leaves the cell with the movement of molecules occurs through diffusion. Diffusion constantly occurs in living cells but the rate of diffusion increases with temperature as molecules gain kinetic energy and move more. Hypothesis The greater the temperature of the water bath the darker the water will be, as more pigment leaks out of the beetroot.
Cut sections of uncooked beetroot using a size 4 cork borer and place the sections in distilled water overnight to remove excess dye. Then cut these sections into slices 1cm in length, so there is 8 pieces, one for each water bath. Set up 8 water baths ranging from 0°C to 70°C going up in 10°C increments and place 8 test tubes containing 5cm³ of distilled water, one in each of the water baths to bring them to the required temperature. Place a beetroot section in each boiling tube and leave for 30 minutes. Set up the colorimeter for 490 nm light absorption, and 2/3rds fill cuvettes with water from each of the 8 boiling tubes. Calibrate the colorimeter and put in the cuvettes, taking care to place them so the light passes through the smooth sides, and record the readings. Repeate the readings for all 8 temperatures to check results are correct.
Dependant Variable - Colour change of the water due to the betalains pigment,being leaked.
Independent Variable - Temperature of the water bath into which the beetroot is placed
Temperature °C | Absorption at 490 |
0 | 0.03 |