Beetroot Practical Experiment

For this Beetroot experiment, the aim was to find out the effect if different types of conditions the beetroot is placed in will affect the permeability of the cell membrane of the beetroot.

 

Apparatus used for the experiment 

There were 5 tubes in this experiment, A to E. 

Tube	Content
A (Control)	5 pieces of beetroot in 4 ml water
B	5 pieces of beetroot in 4 ml 25% alcohol
C	5 pieces of beetroot in 4ml 50% alcohol
D	5 pieces of beetroot in 4ml hot water
E	5 pieces of beetroot diced into smaller pieces in 4ml water

 

We put 5 small pieces of beetroot (approximately the same size) into each tube (with different contents as shown in the table above) for about 15 to 20 minutes.

From left to right: E, C, B, A

Tube D

 

After 15 to 20 minutes, we noted the colour change of the solution in the tubes. However, I acknowledge that we did not shake the tubes so that the red pigments were evenly spread out throughout the solution at this stage.

 

Colour of water at the end of experiment

 

 Colour of 25% alcohol solution at the end of experiment

 

 Colour of 50% alcohol solution at the end of experiment

 Colour of hot water at the end of experiment

 Colour of water at the end of experiment

(Note: The solutions turned red due to the red betacyanin pigments in the beetroot cell sap that diffused out the the cell and into the tube.) 

Next, we poured all the solutions into cuvettes after shaking. 

Final colour after experiment. From left to right: A, B, C, D, E.

 

At the end of the experiment, the water in tube A was very light pink, the 25% alcohol solution in B was light pink, the 50% alcohol solution in C was pink, the hot water in D was red and the water in E was reddish-pink.

Next, we took readings from the colourimeter.

Light transmission value of solutions shown on the Colourimeter

 

This shows that the darkness of the solution corresponds to the light transmission value. (ie. The darker the colour of the solution, the lower the light transmission value).

From the results, it is apparent that tube A had the highest light transmission value as no harm has been done to the cell wall, cell membrane and tonoplast of the vacuole. Hence, diffusion of the betalain pigments out of the beetroot cell was very low. In Tube B, the light transmission value was 86.71% as the 25% alcohol solution causes damage to the cell, causing the betalain pigments to be able to flow out of the cell more easily, thus turning the solution light pink in colour. As for tube C which contained 50% alcohol solution, the cell membrane and tonoplast were damaged even more than that in tube C due to the high alcohol solution, causing even more betalain pigments to diffuse out of the cell, causing the solution to turn pink in colour. The beetroot pieces were placed in hot water in tube D. High temperatures will cause the weakening in the forces holding the polypeptide chains in the cell membrane together, leading to the betalain pigments leaking out of the cell. This caused the hot water to turn red and hence, it has a very low light transmission value of 5.43%. Lastly, tube E with the beetroot cells of larger surface area would also have a lower light transmission value than the control (tube A) as the increased surface area will lead to a higher rate of diffusion of the betalain pigments out of the cell.