Diffusion is the movement of molecules where they are in high concentration to where they are in lower concentration, down a concentration gradient. Energy for the movement comes from the kinetic energy of the molecules themselves.
Apparatus.
Method.
I will be applying 7 different temperature ranges, 80 oC, 70oC, 60oC, 50oC, 40oC, 30 oC and 20oC on beetroot pieces to test if the increase of temperature (the independent variable) does have an effect on the release of pigment. The beetroot was cut into 5 cylinders using the cork borer making sure the beetroot cylinders had roughly the same diameter, length and surface area. The external dye (dependant variable) was washed off and dried to maintain the accuracy of the results. A beaker was heated using a Bunsen burner to and 80oC and measured using a thermometer. The Bunsen burner was turned off and the beaker allowed to settle. When the bath reached 80oC a piece of beetroot was placed in the water for 1 minute (dependant variable). When the minute had elapsed, the beetroot was removed and placed into a test tube filled with 10cm3 of distilled water. Distilled water is a clear liquid that ensures nothing should contaminate the beetroot and it is possible to detect the slightest deviation in colour. Then, the fluid in each of the test tubes will be analysed using a colorimeter. The water bath was cooled to 70oC, 60oC etc repeating the procedure. The fluid in each of the test tubes was analysed using a colorimeter and the results were recorded.
Prediction.
I believe that more dye will be released from the beetroot as the temperature increases. High temperatures may distort the active site of the carrier affecting the shape of the fluid mosaic model membrane. The increase of kinetic energy will speed up the diffusion rate of the red pigment to a point then structural damage of the membrane and the denatured proteins will increase the amount of red pigment escaping out of the cells.
Results.
Graph showing release of pigment as temperature increases.
Analysis.
My graph shows a general trend that is, as the temperature increases the amount of pigment released from the beetroot increases to.
My results increased steadily until the steep climb between the temperature ranges of 60oC and 70oC. This is the point where most of the proteins in the cells are being denatured allowing gaps to form and the sudden rush of purple pigment to escape. After that point the graph ‘tails’ off suggesting some of the denatured proteins are blocking the holes created in the first place slowing down the release of the purple pigment.
Basically, it is the input of kinetic energy due to the build up of temperature that increases the rate of diffusion. This in turn will damage and denature the plasma membrane causing substances contained within the membrane to leak out. It is the breakdown of phospholipids in the membrane, which cause gaps to appear allowing fluids (red pigment in this case) to pass through. As the red pigment particles move faster, they diffuse out of the membrane at a faster rate, increasing more as the temperature increases.
Evaluation.
The experiment went well but there were areas to the experiment that could have been improved.
The beetroot cylinders were not always cut accurately, only estimated which obviously alters the effect of the experiment. The temperature (independent variable) in the water baths fluctuated, making it extremely hard to get the desired temperature. The results could have been made more reliable by repeating the experiment more than once and by finding the mean value. After I had cut the beetroot pieces and rinsed them to clean the red pigment leakage I found it hard not to damage the membrane as I tried to dry the pieces off. I had to complete the experiment in just over an hour, which I feel wasn’t long enough. It is safe to say my results are accurate because other students in my class had results that were similar to mine.
Finally, the beetroot gives a good representation of the theories behind the plasma membrane and how it behaves but it does not give a good representation of the whole eukaryotic group because their behaviour may differ to others.
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