Aim: to investigate the Effect of Temperature on Membranes
Background: The colour of beetroot is due to the presence of a red pigment, betacyanin in the cell sap. As long as the cells and their membranes are intact, the betacyanine remains inside the vacuoles in the cells. However, if the membranes are stressed of damaged, betacyanin will leak through the membrane and produce a red colour in the water surrounding the beet tissue. Such stress or damage can be caused by heat. The intensity of this red colour will allow for the assessment of the damage produced by experimental treatment.
Hypothesis: The higher the temperature, the higher the damage done to the cell membrane, and thus the more betacyanin released into the water surrounding the beet tissue. This will lead to a more intense shade of red.
Materials, procedure: [as stated in practical]
Dependent variables: the intensity of the redness in the water
Independent variables: the 6 temperatures of water which the samples were submerged in
Controlled variables: thickness of the discs (3mm), time span which discs are washed in water (5 min), volume of water in each test tube (6ml), number of discs on each needle (6 discs), time which needles are placed in water bath (1 min), time with samples are left in test tubes after being heated (20 min)
* The best fit curve is a very good fit since it is so close to all the points and the number of points lying above and below the curve is balanced. This means that the curve is a very accurate representation of the data.
* The standard error is very small across the 2 samples for each temperature. This shows that the data is probably very accurate since it does not vary much.
* From the graph, it is seen that there is a steady, consistent and linear increase in the absorbancy with increasing temperature.
* This is in line with the background information which states that the higher the temperature, the more damaged the cell membrane gets. More betacyanin is released from the cell vacuoles, leading to a more intense shade of red, therefore resulting in a higher absorbancy. Thus, this supports the hypothesis.
* The results seem to be generally reliable, since they correspond with the understanding of how cell membranes are damaged by heat.
* However, experimental errors could have occurred. For example, due to parallax error, it is difficult to ensure that all the discs are cut to exactly 3mm in diameter. Percentage error can occur in the variations of thickness of discs, leading to inaccurate amounts of betacyanin being released. This would affect the results since we are only looking at temperature as a cause of the higher amount of betacyanin released.
* Furthermore, there is a lag time during the preparation of the tubes. The mounted needle with the discs to be prepared would remain in the test tube for a much longer time than the last needle since after the preparation they are all left for another 20 minutes. Thus the first sample has a longer time for the release of its betacyanin since it is left to wait while the other samples are prepared, before it is given an extra 20 min to wait, just like the rest.
* Besides this, when the discs are cut, the cutting action may damage their cell membranes. Different extents of damage may be incurred by different samples due to the different ways they are cut. This leads to an inaccuracy in the amount of betacyanine released.
* Instead of two samples for each temperature, five could be used and the average obtained. This minimize the chance of inaccuracies of results arising from the other faulty aspects.
* Besides this, each needle, after heated, should be timed and left in the test tube for only 20 minutes. The first one to be put in will also be the first one to be taken out. This will ensure that all the samples have the same amount of time for the betacyanin to be released and therefore ensure a more accurate result.
* Instead of using a blade to cut the beetroot, a hard boiled egg cutter should be used. This can hold the beet root in place and ensure that each disc is consistent in its width. It is also swift and clean in cutting, ensuring that minimal cells are damaged, and even when there is damage done, it ensures that the extent of damage is same to each disc since many are cut at once. Moreover, being able to cut many at once is more efficient and reduces lag time.
* The experiment would be extended to temperatures beyond 80 to find out the temperature at which all the betacyanin has leaked out and the absorbancy no longer increases due to increasing intensity of red.
* The hypothesis is proven true that as the temperature increases, the cell membranes get increasingly damaged and thus release larger amounts of the red pigment betacyanine, causing an increased intensity in the red of the surrounding water, thereby leading to a higher absorbancy.