Safety:
Because we did not prepare the beetroot samples ourselves, there are no specific safety measures to follow except for general laboratory guidelines such as wearing a lab coat and perhaps safety goggles.
Results: Table to show the absorbance of light from mixtures of distilled water and beetroot pigment solutions
Analysis:
We did this experiment to determine how increasing the temperature of the cell would affect the amount of pigment leaked into the surrounding water, and therefore how much light would be absorbed when tested with a calorimeter. By increasing the temperature of the water baths, we gave more energy to the molecules in the liquid of the vacuole, causing the mixture to expand. This results in rupture of the tonoplast.
The membrane of the vacuole, known as the tonoplast, is very similar to the cell membrane in that it has a double layer of phospholipids, with both layers pointing the hydrophobic, tail-shaped fatty acids into the ‘sandwich’ of the two layers. On the edge of the lipid bilayer there are hydrophylic phospholipids, which are spherical. Phenolics, acids, and a range of nitrogenous wastes are held in the vacuole in a gel like watery substance, away from the cytoplasm. Pigments are stored alongside them in this solution.
Proteins are formed of coiled and folded strings of amino acids and are generally very strong. But add too much heat to them and they will unwind, causing them to break apart. This happened to the proteins in the vacuole membrane, causing them to become unstable. The lipids themselves also become much more watery as they increase in temperature, so the membrane becomes fragile. Add this to the already unstable proteins, and the vacuole is likely to break,
When we added heat to cell, every molecule began to vibrate, the most vigorously being water particles because they are so small. This causes damage to the membranes and organelles, preventing them from holding liquids in particular places and allowing the solutions to escape. Also, as the liquids heat up they will expand, pressing against the already-flimsy membranes and causing the separate compartments to burst.
The data collected form our result is fairly simple to explain – the more heat added, the more pigment will be released as more damage is done to membranes within the cell. According to our results, temperatures up to 50˚C all had very little effect on the cell, and the pigment measured would probably have been released with no interference from us. But after that there is a huge difference between each reading where there was none before. This may be because the cell has a temperature threshold – it can withstand temperatures of up to a particular heat, but after that the membranes are not strong enough and eventually the cell dies. This maybe because in some hot climates temperatures can reach almost up to 50˚C, yet the beetroot has no outer protection to keep out heat. Therefore evolution has allowed the plant to grow to withstand high temperatures without serious damage.
Evaluation:
Our results do not present any obvious anomalies. This is likely to be because we only carried out a simple procedure, with minimum possibilities for error. Our beetroot pieces were cut by technicians and were precisely measured, although we could have taken more care to check whether or not the technician had made a mistake. But the size differences were not visible to the naked eye, and had no obvious effect on our results.
One way we could have been more careful was with our water baths – because we did not monitor the temperatures of the water baths during the thirty minutes, it is likely that each water bath lost a lot of heat and the temperature differences between the beginning and end of the experiment were large. If each bath were losing heat at the same rate, then this would not be a problem, but because each container began at a different temperature, each would have had a smaller or bigger difference in temperature to the room, so each would lose a different amount of heat. Plus, our baths at 60˚C and 50˚C remained in carefully monitored shared water baths, so there would have been no heat loss. This means that our results for these two temperatures were probably too high and therefore inaccurate.
Human error can also contribute to inaccuracy – it is possible that not all of the pieces of beetroot were in exactly the same amount of water, which would mean that some solutions of pigment would be more diluted that others, causing a lower absorbancy to be read on the calorimeter.
There is also a limit to the accuracy of the calorimeter – it can only measure to 0.01 accuracy, so there may have been small differences that we were unable to record, and therefore a possible error of +/- 0.005 on each of our results. This error is unlikely to make a significant difference to the general accuracy of our results.
If I were to repeat the experiment I would keep each water bath in a temperature maintained environment, so that there is much less heat loss, and a smaller difference between heats lost for different temperatures.
I would not use a more accurate calorimeter, as over all there was only a slight chance of fault, and at this level there is no need to gain any more accurate results as can be obtained with this particular device.
Conclusion:
To a certain extend, the results gained matched our hypothesis; there was a positive increase in pigment released and therefore absorbancy, alongside increase in temperature. But it was not a perfect positive correlation – for a lot of our cooler samples, there was very little difference between each piece of collected data. The hypothesis was almost scientifically justified, and the results were collected precisely and then unexpected occurrences explained. The method used was sufficient for proving or disproving the hypothesis we proposed.
Bibliography:
http://www.cellsalive.com/cells/plntcell.htm
http://koning.ecsu.ctstateu.edu/cell/vacuole.html
http://www.omedon.co.uk/ionchan/membrane/membrane.jpg
http://www.madsci.org/posts/archives/nov2001/1006025567.Cb.r.html
Student sheet: Why does the colour leak out of cooked beetroot?