Apparatus: Materials:
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Stopwatch
- Colorimeter
- Variety of water baths
- Number of test tubes
- Beaker
- Cork borer
- White tile
- Knife
- Pipette
- Test tube rack
- Thermometer
- Ruler
Method:
- “Place 5 labeled test tubes each containing 5cm(3) distilled water into water baths at 0°c, 20°c, 40°c, 60°c and 80°c. Leave for at least 5 minutes until the water reaches the required temperature.
- Cut sections from a single beetroot using a cork borer on a white tile. Cut five 1cm length slices from these sections.
- Place the slices of beetroot in a beaker of distilled water and leave for 2 minutes to wash away the dye from cells damaged by the cork borer.
- Place one of the beetroot sections into each of the test tubes. Leave for 20 minutes in the water baths.
- Decant the liquid from each tube, into a clean; labeled test tube ensuring the beetroot disc stays behind.
- Switch the colorimeter and set it read % absorbance. Set the filter to the blue/green filter-490nm.
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Measure 3cm(3) distilled water into a cuvette. Place the cuvette in the colorimeter ensuring that the light is shining through the clear sides. Zero the colorimeter (R button)
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Measure 3cm(3) of one of the dye solutions into a colorimeter cuvette and take a reading absorbance (T button) repeat the readings for all the dye solutions.”
Data Collection and Processing:
Table of results:
* Average calculation: (sample 1 + sample 2 + sample 3 + sample 4 + sample 5/5) for each temperature*
*Significant trend from results table: by looking at my results table, I can see that as the temperature increases, the average absorbance % increased to. Therefore they are directly proportional.
Standard Deviation:
Graph Analysis:
From my graph it is clear that as the temperature increased, the rate of absorbance also increased; directionally proportional. The temperature increased steadily, to an extent, however when it reached 40c, the absorbance percentage increased rapidly and started to level out at 60c. In addition to this, as my error bars show in both my graph and table, that not all my data was under 0.05 therefore I can not put the errors in my results down to chance and errors in my experiment, I will discuss later.
Conclusion:
I can conclude, from my graph, that there is a general trend in my results. The trend is that as the temperature increases the mean percentage of absorbance increased too. From temperatures 0-40 (C) there was a gradual increase however, as the graph shows, it increased rapidly from temperature 40 to 60 and then gradually leveled out between 60-80 degrees.
The graph clearly shows how an increase in temperature can affect the membrane activity (which is shown through the absorbance percentage using a colorimeter.) The steep incline shown on my graph (between 60-80 degrees) represents the point in which the protein in the membrane cells are becoming denatured (due to the increased temp) and allowing more of the red pigment to leave the cell. The cell membrane has a phospholipid layer, which is made up of fatty acids and when it is placed in a high temperature, the layer becomes more fluid and therefore becomes more delicate. When the carrier proteins in the cell membrane become denatured (the optimum temperature for enzymes is between 10-35 degrees approx.) they form holes and destroy the delicate layer in the membrane. This results in the beetroot pigment ‘bleeding’ through and any pigment in the membrane will now exit the cell. This is represented between 40 degrees and 80 degrees in relation to the absorbance level increasing.
With reference to my hypothesis, the increase in temperature will increase in the amount of kinetic energy as the water will be hotter and expand resulting in more vibrations will pass through the water (kinetic energy), which will result in an increase in the diffusion rate of the pigment. Once the temperature reaches above approx. 40 degrees, the cell membrane plasma will denature due to the surrounding temperature being too high and consequently the beetroot pigment in the cell membrane will eventually leak out. However, at lower temperatures, less damage was done to the cell membrane. This was done by smaller amounts of pigment diffusing through the cell membrane and therefore absorption percentage was lower.
In conclusion, the temperature affects the activity of the cell membrane as the temperature increases. This is due to the fact that the carrier proteins in the cell membrane denature with higher temperatures as it becomes too hot for them to function. The change involving the phospholipid layer structure also results in the membrane becoming less stable and therefore more of the beetroot pigment is able to escape the membrane in addition to more carrier proteins destroyed.
From my graph and error bars I am able to say that for 0 and 40 degrees, the possibility that our results are just chance are under 0.05% and therefore we can be certain that our results are reliable due to this small percentage. However when looking at the other error bars, the percentage of error is quite high so consequently, it is more likely that a number of errors or mistakes contributed to the results that I got.
Evaluation:
From my data, it was evident that my results were not as accurate as they could have been and there are a number of factors that could contribute to my level of accuracy and the results that I got. The fact that my results follow a genuine trend suggests that my data was not far off however compared to some of the other students, a few of my results were different by a large extent and this can be seen evidently in my data table.
However, by taking an average, which I did with each sample I think that this can show a level of accuracy with my results as because I had 5 samples, I was able to add all the results together to find a mean of the data and then plot this on a graph. In addition to this, by using a control sample of water to test the colorimeter, it meant that I could prove my colorimeter was working properly as when tested, it gave the correct absorbance percentage. Other procedures I used to ensure that variation and errors were kept to a minimum were all the beetroot cylinders were cut with the cork borer and I used a stopwatch to ensure that all test tubes were kept in for the same amount of time.
If I had to do the experiment again, another variable I could measure, instead of temperature is how the PH affected the cell membrane activity.