Independent variable (iv):
Temperature of distilled water in the test tubes containing beetroot, placed in incubators of temperatures ranging from 20-70°C
Dependant variable (dv):
Absorbance (arbitrary units ranging from 0-2) of light by betalain, which is dependent on the amount of red pigment released
Fixed variables:
Reliability:
The experiment will be repeated six times so that an average can be taken. This will be combined with the class results. Taking averages can account for any anomalies that may occur in the experiment.
Safety issues:
Care must be taken when using the cork borer as it may hurt you while trying to get it in to the beetroot. In addition, lab coats must be worn as you are always using beetroot and they are around you, so you must be careful that the beetroot juice does not get to your cloths as it may stain. Also, the test tubes that will be placed in the colorimeter must be dried before place in the colorimeter as water conducts electricity, and may cause an electric shock. Finally, the water in the water baths reached temperatures up to 700c.
Detailed method:
A modified method was used by all class members so that the results could be compared.
1) Cut sections from a single beetroot using a size 4 borer. Cut eight, 1 cm length slices from these sections. Be careful not to spill beetroot juice in your skin or clothing, as it will stain very badly.
2) Place the slices in a beaker of distilled water. Leave for 10 min to wash away excess dye.
3) Next, place eight labelled boiling tubes containing 5 cm3 distilled water into water baths at: 200c, 300c, 400c, 500c, 600c, and 700c. Leave for 5 minutes until the water reaches the required temperature. Place one of the beetroot sections into each of the boiling tubes. Leave for 20 minutes in the water baths
4) Remove beetroot sections (dispose of them in the bin); shake the water/ solution to disperse the dye
5) Switch on the colorimeter as set it to read “%” absorbance
6) Set the filter dial to the blue/green filter (why?)
7) Adjust the colorimeter to read “0” absorbance for clear water. Do not alter the setting again during the experiment.
8) Make sure that the tubes (with the coloured solution) are dry. Place the tube in to the colorimeter and take the reading.
9) Repeat the reading for all the temperatures
10) Combine your data for absorbance with other groups to produce a class set.
Interpretation of results:
My data shows an increase in the temperature as the absorbance increase which means that it supports my hypothesis; “as the temperature increases, the amount of betalains leaking from the beetroot membranes increases.” The reason behind this could be that Beetroot cells contain a red pigment, which is stored in the cell vacuole. When higher temperatures above 500c denatures the protein, then the dye will pass through the membrane and into the solution.
Therefore, the more dye that has passed into the solution, the more denatured the proteins have become and the more damaged the membrane will be.
This may mean that my data is reliable but there may occur some random errors in the data.
My data shows an increase in the absorbance of the beetroot pigment when the temperature increases. From 200c to 500c the absorbance of the beetroot pigment started to increase slowly but when the temperature increased to 600c, the absorbance increased dramatically. Overall my data supports my hypothesis and as the temperature of the water baths increases the absorbance of the beetroot pigment increases, this is because heat effects the proteins in the cell membrane and so if the protein id denatured by the heat, the membrane will become damaged and so red dye will leak out of it. So the higher the temperature, the more damaged the membrane becomes and so the more dye will leak out.
Evaluation:
In my data there could have been some anomalous results, this might be because of the equipment that has been used in the experiment.
My graph shows that my results are not very precise as they were not close to each other due to the dramatic increase in 600c. However, at the beginning from 200c to 500c my results were precise as they were quite close to each other. In addition, the error bars that I have included in the graph have got bigger and bigger but in 600c they decreased and then increases again dramatically to a very big bar at 700c.
As to the accuracy of the results: according to research obtained from madsci website, “… many proteins are denatures by temperature at around 40-500c, but some are still active at 70-800c and few even withstand being boiled…” (5)
Systematic errors:
According to my results at 60-700c the absorbance of beetroot pigment start to increases dramatically and this is due to proteins denaturing. This could be due to the filter on the colorimeter or another reason could be that if a larger volume of distilled water was used then the absorbance would be higher and so effect all of your results.
Random errors:
Random errors also occurred in my results and this is due to the water temperature; as they could change without us noticing. Also, the position in beetroot in which cells were taken differed which may have effected the concentration of betalains in beetroot cells. In addition, everyone in the class used a different size 4 borer and they might be different sizes. And finally, slices of beetroot we supposed to be cut 1 cm, but each group may have been slightly have cut different sizes as the rulers are not accurate. The ways in which the experiment could be improved in order to make the results more reliable and valid could be by:
-
everyone in the class using the same borer
-
monitoring the temperature of the water baths at all times
-
using the same colorimeter
- everyone cutting from same position of the beetroot
Summary/conclusion:
The aim of doing this experiment was to see the effect of temperature on the release of betalain from beetroot cells. This was done by taking six relatively identical pieces of beetroot and placing them in different water-baths at different temperatures and testing how much betalains pigment leak out of cell across membrane. I found a positive correlation between the temperature and the amount of pigment that was released. This is due to the temperature the protein denatures which therefore damages the cell membrane and so cause the betalains to leak out of it as the temperature of the water baths increased.
Bibliography
Table of results:
