University of Manchester Pharmacy with foundation year
PHBY01 Coursework Practical
The Effect of Alcohol Concentration on the Leakage of Pigment from Beetroot Cells
1) Method (6 marks)
· Firstly, we began with making the alcohol concentrations using the stock alcohol solution and water provided in order, to prepare a series of six test tubes each containing 10cmᶾ of different concentrations of alcohol. We ensured the concentrations were equally spaced and covered a range from pure water (0%) to pure alcohol (100%).
· The solutions that were made up in the experiment carried out were as follows:
Volume of alcohol/ cmᶾ
Volume of water/ cmᶾ
Total volume of solution
Concentration of alcohol solution/ %
· These solutions were then made up in individually labelled test tubes and placed in a room temperature water bath.
· After this, we cut 12 discs of beetroot using a ruler measuring 1mm in thickness ensuring all beetroot cylinders are of uniform thickness.
· We then used the strainer to rinse the beetroot discs under the tap each piece to remove the excess red dye that leaked during the cutting procedure.
· Then we added two pieces of the 1mm beetroot cylinders to each of the 6 test tubes containing the different concentrations of alcohol solution, ensuring this was done at the same time for each.
· We then placed the test tubes in the room temperature water bath that was made up before for 5 minutes. Whilst they were in the water bath, the tubes were gently shaken several times to allow the beetroot and alcohol to mix and for reaction to get to equilibrium.
· Once the 5 minutes were up, we immediately removed the tubes from the water bath and decanted each solution into a clean corresponding labelled test tube, leaving the beetroot discs in the original test tube.
· Then it was time to use the colorimeter – before using the colorimeter we had to set the absorbance and the wavelength to 530 nm. We prepared a blank by filling a cuvette with the 0% alcohol solution to calibrate it. To correctly use a cuvette, we had to: Wipe the outside of each cuvette, Handle cuvettes only by the top edge of the ribbed sides, dislodge any bubbles by gently tapping the cuvette on a hard surface. And position the cuvette so the light passes through the clear sides (side of triangle on left).
· Once this was done, we measured the absorbance of each solution by pouring each solution into the cuvette each time with the same cuvette for each reading however ensuring excess was cleaned, before using a different solution.
· The thickness of the beetroot is a confounding variable we have controlled – we ensured the same level of thickness approximately for each disc.
· The same cuvette was used in the colorimeter as no cuvette is the same will always be slight differences in their composition that can change your data. By using the s...