Required Practical 4 can investigate a variety of different variables, including temperature and solvent concentration.
- However, it uses beetroot as it contains a pigment called betalin.
- The more pigment that leaks out of the cell, the more permeable the cell membrane is.
How do you investigate the effect that temperature has on the permeability of cell membranes?
- Use a scalpel to cut 5 equal pieces of beetroot - rinse the beetroot to remove any pigment that is released during cutting
- Put each piece of beetroot in a different test tube, each of which have 5cm^3 of water measured using a pipette or a measuring cylinder
- Place each test tube in a water bath at a different temperature for the same length of time
- Remove the beetroot from the test tubes
- Switch on a colorimeter and leave it for 5 minutes so it stabilises
- Set up the colorimeter so that it is using a blue filter or a wavelength of about 470nm
- Add distilled water to a curvette and put it into the curvette so that the light passes through the clear sides.
- Calibrate the colorimeter to 0 and use a pipette to transfer some liquid from the first test tube into curvette
- Put the curvette in the colorimeter, read and record the absorbance of the solution
- Repeat steps 8 and 9 for the other 4 test tubes