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Beetroot practical

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Why does the colour leak out of cooked beetroot? The aim of this experiment is to investigate the effect of temperature on membrane structure. I predict that as the temperature of the water in which the beetroot is placed increases, the amount of pigment leaked will increase. My prediction is based on the concept that cell membrane will breakdown as the temperature rises. Apparatus * Corer * White tile * A Beetroot * Automatic Water Bath * Segregated knife * A thermometer * Stopwatch Method: * First I took the white tile and the corer. Then collected a cylinder of beetroot by pushing the corer into the beetroot and withdrawing it. The cylinder remains inside the corer. * I collected 2 cylinders, and cut them into 8 pieces of 1 cm with a segregated knife. Because the beetroot has been cut some of the cell membranes had been broken, which means some pigments leaked out. ...read more.


Temperature % of absorbent 0 81% 10 110% 20 86% 30 103% 40 90% 50 15% 60 7% 70 8% (see graph next page) Analysis Through observation from the line graph that I have constructed it is quite certain that there is a similar pattern. There is a steady speed increase represented by a positive correlation. It shows that as the temperature increases the percentage of absorbance also increases. This means that more pigment diffused through the beetroot's cell membrane at higher temperatures. There is one exception, which is the beetroot that was situated within the cold water as this shows an absorbance of 0%. Evaluation There were a number of sources of error that may have affected the accuracy of my results. Firstly I had one stopwatch and timed all the water baths for fifteen minutes, so there was a slight delay however between the placing of the tubes in each water bath, as I had to walk to each water bath so it would have affected my reults slightly. ...read more.


It would also have been better to have had the time to repeat each temperature more times to make the results more reliable. Another limitation was cutting the beetroot into pieces. The pieces cut had roughly the same surface area to volume but not exactly the same volume. This would have had a slight effect on my results because the rate of diffusion of betalain particles across the plasma membrane is increased, as the surface area of the beetroot increases. So the slightly thinner and smaller pieces of beetroot I cut would have released more betalain from their vacuole. Conclusion I conclude that there are no apparent anomalies in my results and none of my sources are deem enough to make my results unreliable. However the sources of error and limitations in my results may have made my results slightly less accurate, but other students in my class found the same. ...read more.

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Here's what a teacher thought of this essay

** This is a very limited piece of coursework that is lacking in a number of key areas that are needed to gain a good grade at A level.
To improve:
Research and Rationale.
There is no background theoretical material included in this report. Additional sources beyond readily available textbooks should be used to provide a context for the experiment and to assist in the planning. References should be included.
Planning. More thought needs to be focused on the key variables. Many of the important variables to be controlled are not described. The apparatus is listed but needs to be justified and full details included. The range of temperatures is identified but there is no indication as to why this particular range was chosen. No suggestions for repeating the collection of data are included. A pilot experiment would be helpful. There is no safety information included which is now a requirement for many examination boards.
Implementing. The data needs to be recorded in a suitably headed table and the precision of the data (only to one percentage absorbance unit) could be improved. Since only eight readings were recorded no data processing was appropriate and this would lose credit.
Analysing and Evaluating. No graph was included. The trends in the data need to be described correctly and the results should be explained using reference to basic biological knowledge. The limitations of the results should be discussed. The candidate needs to include suggestions for improving the reliability of the method.

Marked by teacher Stevie Fleming 26/07/2013

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