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For this experiment, I am investigating the effect of temperature on the permeability of a beetroot membrane. First thing I did was I measured out 5 100cm³ of distilled water, and placed them into 5 different temperatures. Using the cork borer, I cut out one cylinder for each temperature, and then trimmed to a length of 2.5cm. After, I put the trimmed beetroot into the 5 different temperatures and left them for 25minutes. After 25miutes, I decanted the liquid containing the leaked beetroot pigment at each temperature into a cuvette, and then placed it into a calorimeter which has a blue filter. Then I measured the percentage light transmission for each temperature. And lastly I collected results for others in class to use it for comparison.


I believe that more betalain pigment 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 the structural damage of the membrane and the denatured proteins will increase the amount of red pigment escaping out of the cells.


Table to show the percentage light transmitted through a beetroot pigment (betalain) at different temperatures in an experiment to investigate the effect of temperature on the permeability of a beetroot membrane.

  • These are all the group results.
  • My results are the first set of results
  • The anomalous results are in bold italics.


Mean of class calculated to give more reliable data for conclusion and to use it to produce graph and standard deviation.

Looking at the result table and the graph produced from the results obtained form this experiment; it shows that as temperature increases, the percentage transmission decreases. This tells us that temperature does affect the membrane, resulting in more leakage of the red pigment. The beetroot solution appears as a red colour and this is caused by the betalain pigment contained within the vacuole of beetroot cells.

An overall description of the graph shows that as the temperature increases, the percentage light transmission decreases. Increase in temperature shows that more pigment is leaking out of the membrane, showing the membrane as getting more permeable.

From 0ºC to 18ºC, it shows that low temperature has little effect on the beetroot’s membrane, because there’s a very slight decrease of light transmission (shown by observing the graph, there’s a slight decrease of light transmission between the two temperatures). This is because the temperature is too low, resulting in the beetroot’s particles having less kinetic enerygy, with the betalain pigment having less energy for a collision to occur. The low temperature won’t cause much damage to the beetroot’s membrane because the phospholipid bi layer has prevented the betalain pigment from leaking out due to polarity; because the phospholipid bi layer acts as a barrier to stop water soluble from moving in and out of the membrane. And since the betalain pigment is water soluble, at low temperatures, the phospholipid bi layer is still acting as a barrier, stopping it from leaking out of the beetroot’s membrane.

From 18ºC to 35ºC, there’s a rapid decrease of light transmission (and looking at the graph, it shows the biggest steepness out of all the other temperatures). This is due to the input of kinetic energy due to the build up of temperature that increases the rate of diffusion, and the increase in temperature causes a vibration. This in turn will damage 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.

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At low temperatures e.g. 0°C to 35°C, some tonoplast (vacuolar membranes) and the cell membrane will leak into the surrounding water but at a much higher temperature, the tonoplasts of the cells will break down completely, resulting in a massive release of betalain pigments. Because the temperature has not gone beyond what the membrane is supposed to withstand, the permeability of the plasma membrane was not really affected at low temperatures (5°C to 35°C). But since the temperature has goes beyond limits that the membrane can withstand (temperatures from 35°C upward), then liquid solution (betalain pigment) in the membrane ...

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