The effect of temperature on the cell membrane of a beetroot.

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In this experiment I will be testing the effect of temperature on the plasma membrane of a beetroot. I will do this by measuring the percentage light transmission using a spectrophotometer. Once I have obtained my results, I will justify them using scientific knowledge explaining what I have observed whilst carrying out the experiment.

Factors to be controlled

"« The pH concentration

"« Regular use of distilled water

"« Ensuring that the surface area of each piece of beetroot is the same

"« Use the same volume of water

"« Start with the required temperature before placing the beetroot into the boiling tube.

"« Use a new piece of beetroot for each experimental temperature

"« Ensuring that the boiling tubes are left in the water baths for the same amount of time

Through secondary research I found that if I were to prevent the structure of the protein from altering in any way, I would need to keep the pH level constant. Subsequently, I decided to will be using distilled water throughout the experiment as it has a pH 7 and is neutral; neither acid nor alkali. By surrounding the beetroot with distilled water the protein will not have been altered, and the concentration gradient will be fairly constant for each of the temperatures also. This is because I will be exposing the beetroot to the surroundings of the same type of water, maintaining a fair test as distilled water may contain less or more impurities as other types of water, for example: tap water. I will have to control the amount of distilled water I use to place the beetroot pieces in and control this by using a measuring cylinder. I will measure 15cm3 of distilled water each time. It is important to keep the amount of water constant, as the dilution will affect the rate of diffusion, therefore affecting the results.

Another factor that I will be controlling is the surface area and mass of the beetroot pieces used. This is because the surface area affects the rate of diffusion, thus affecting the results. This will be done with the aid of a cork borer with which I will measure each beetroot piece with a ruler to 20mm. It is unlikely that their masses will be identical but I will do a visual check to make sure they are the same size, however I will later evaluated how this may or may not have affected my results.

As one particular section of beetroot will only contain a certain amount of pigment, I will be using a separate section for each test tube. As no two pieces of beetroot can be identical, possible differences in permeability and temperature can occur. Therefore, I will make note of this when evaluating my results, and consider how this may have reflected on my results.

Another factor I will need to take into consideration to create a practical and fair test, is to assure that the pigment is not left to stand for too long. This would cause the pigment to settle at the bottom of the test tube giving me an inaccurate reading of light transmission. Another way to prevent this from happening would be to shake the test tube in order to dissolve any pigment that has settled at the bottom of the tube.

I will also be controlling the amount of time the solutions are left at their designated temperatures, as unequal time spans will results in unfair results. In order to do this, I will be using a stop clock and allowing each solution to be at the desired temperature for 3 minutes.


The main variable in this experiment will be temperature as I am trying to find out how this specifically affects the cell membrane. In order to certify that the results obtained differ due to the changes in temperature, I will repeat the same experiment three times, in the same temperature of water, for the same amount of time. This precaution of repeating my results is used to ensure that my results are reliable, and to identify any anomalies. These experiments will be set up at room temperature. The percentage light...
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