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Materials:
Beetroot Plant Corers (various diameters)
- White tile
- Bunsen burner
- Tripod
- Gauze
- Beaker (for water bath)
- Thermometer
- Colorimeter
- Distilled Water
- 7 test tubes
- Tongs
- Scalpel
- Stop-clock
- Test tube rack
Method
- Cut 7 slices of beetroot approximately to 4cm. They must all be the same size to
ensure this is a fair test, besides the size of the beet. As different length would have
different effect of temperature on membrane permeability. Caution when using knife.
- Wash the strips of beetroot and place in distilled water. This is to ensure all the
colour is washed out. As when cutting the beetroots which may cause the breakage of
the cell walls.
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Heat a water bath to 70°c . Only half fill the water bath to avoid spillage when pieces
of tissue are added.
- Prepare 7 test tubes containing 15cm of distilled water. The same amount of water is
used to control another feature of the experiment. This is another controlled variable.
- Immerse one of the beetroot strips in the heated water for exactly one minute. This
controls another variable and makes the experiment fair.
- Transfer the strip to one of the tubes of distilled water and label the tube with the
temperature of treatment and the time the strip was placed into the tube.
-
Repeat the experiment at 60°c ,50°c, 40°c ,30°c . Do this by adding cold water to the water
bath. The temperature is the only factor that should vary in this experiment. It is the
uncontrolled or key variable.
- Place the sixth strip in distilled water with room temperature.
- Freeze the final strip, wash and place in the seventh tube of water.
- Leave each slice in the water for 30 minutes. Again the time is controlled and thus is a
controlled variable.
- Remove the strips of tissue after the required time, shake the tube, and transfer the
solutions to a colorimeter tube.
- Place a green filter in the colorimeter. As beta cyanin which is the colour of the
beetroot leakage is red, hence all the red light would be absorbed if there is no
change to the filter. With the use of green filter, green light will only be absorbed
and the red colour of beta cyanin would reflect.
- Calibrate the colorimeter using distilled water as a blank and then take the reading of
your 7 solutions in % absorption units. Use the same colorimeter tube for all the 7
readings.
Results
Conclusions:
After collecting and correlating the results, I have come to the conclusion that the
experimental hypothesis is correct in that an increase in temperature will damage
and denature the plasma membrane and cause the cytoplasm and other
substances contained within the membrane to leak out. This has been shown by a
steady decrease in beta cyanin leaked out of plant cells as the temperature
increases referring to the % of absorption.
The graph can be analysed into three parts, first part there is a rapid decrease of
the % of absorption from –5°c to 24°c which is the room temperature. From the
data that are shown beetroot has the darkest % of absorption at –5°c . This is
related to the environment that the beetroots grown. Since beetroot is a root
plant hence it is grown underground which would explain why beetroot has the
darkest % of absorption at –5°c since during winter, the UK is particularly cold
especially under ground. When it reaches –5°c , the cell of the beetroot freezes,
Thus cell burst and beta cyanin leaks out causing the relatively high % of
Absorption.
Between 24°c to 40°c , there is a decrease of % of absorption which following with a
steadily increase. The lowest % of absorption is at 30°c, which would mean that is
the optimum temperature for enzyme substrate reaction since there is a minimum of
plasma membrane being broken.
From 40°c onwards, there is a steady increase of % of absorption, which indicates
that protein within the cell surface membrane has been denatured, hence it can
no longer controls the entry and exit of chemical substances in and out of the
cells. Result in, more beta cyanin being leach out which leads to increasing % of
absorption. However the % of absorption of beta cyanin were not as high as
from –5°c , this is as a result of denatured proteins blocking some of the holes that
appears in the cell surface membrane which is make up of breakdown of the lipids,
these holes allow fluids to pass out freely. That also explain why cells cannot
maintain life in extreme temperatures.
Evaluation:
The results that were collected follow the same pattern as results collected by similar
studies carried out within our class, so therefore it is safe to say that the results can
be repeated reliably and the methods can be used universally. However, we used
different beetroot within our class, which may cause a slight variation to the results
since the beetroots we used may not be grow at the same place or under same
weather conditions.
It would have been beneficial to have repeated the experiment more times to make
certain that the results were not gained through chance or by an external factor. The
control experiment used was highly accurate, using distilled water, which is the
clearest possible liquid, meant that even the slightest deviation in colour could be
detected by the colorimeter.
Controlling the variables in the experiment is not an easy task. The first major problem
is the size of the beetroot piece. The pieces could be the same mass, but have a very
different surface area to one another and the beetroot slices are possibly taken from
the different part of the beetroot, i.e. if the beetroot slice is taken from the xylem and
phloem, which might to lead to more leakage as they transport water, ions, minerals
and products which are formed by photosynthesise. This obviously alters the effect of
the experiment. The other difficult variable to maintain was the temperature of the
heated water. With only basic equipment, keeping the water at the correct
temperature was made a complicated task, besides the effect of temperature between
–5 °c to 24°c were not carried out hence the graph is not in great deal of accuracy. There
are also some percentage error in the equipments that are used, such as measuring
cylinder, which it is an error with 0.1cm. A pipette should be replace in order to achieve
more accurate results. External variables were well controlled. If the experiment was
to be repeated, the use of a proper controlled water bath may be a consideration, and
also a template made for cutting the beetroot pieces.
Using a beetroot as the sample is not a good representation of the whole eukaryote
group. Other cell membranes may have better or worse heat tolerance, some may not
be affected at all, however, using a beetroot does give a good representation of the
theories behind the plasma membrane and how it behaves.
For further work, we are alter the controlled and key variables of varies experiment, such as
using different concentration of alcohol, since alcohol can break down lipids that are within
the cell surface membrane, which will also should the effect of alcohol on membrane
permeability.
