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Effect of temperatures on the permeability of beetroot cell membranes in
Latvia
Research · September 2020
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Paula Abola
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Effect of temperatures on the permeability of
beetroot cell membranes in Latvia
Research paper written by ​Paula Abola​ (BSc Medicinal Chemistry)
Research question​: What effect do the temperatures in Latvia have on the
permeability of beetroot cell membranes to carry out oxygen absorption via
simple diffusion?
Background information: ​The beetroot is the taproot portion of the beet
plant. It is a variety of the ​Beta vulgaris ​plant. Beets are used as a food, food
colouring and a medicinal plant. (1) In beetroot cells, along with water and
other molecules, the vacuole contains a pigment called betalain. This pigment
gives the beet its characteristic red colour. When the conditions become
warmer, the cell membrane is disrupted, causing the vacuole to release
greater amounts of betalain through the more permeable membrane. (2)
Beets are a very common vegetable grown in Latvia. The vegetable is used to
prepare national meals. During the process, it is possible to notice that
different amounts of betalain are released from the beets at different
temperatures. In theory, it is due to the temperatures distracting the cell
membrane. This phenomenon caused me to question whether the
temperatures in June, the beet growing season in Latvia, affect the
permeability of beetroot cell membranes, which is important for oxygen being
absorbed by beetroot cells via simple diffusion to provide the plant with
enough oxygen to carry out aerobic cell respiration and stay alive.
Simple diffusion involves nonpolar molecules such as oxygen passing
between the phospholipids in the cell membrane. This process can happen if
the phospholipid bilayer is permeable enough to let the particles move from
an environment of higher concentration, in this case, the soil, to lower
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concentration, the inside of the beetroot cell. (3) This process is affected by
several factors: the concentration gradient, the distance of diffusion and
temperature. The most important of these factors is temperature. It has the
greatest effect on the rate of diffusion and is the easiest condition to change.
Temperature increases the energy of the oxygen particles, making them move
faster and allowing them to spread throughout the volume. (4)
Aerobic cell respiration is the process of the cell that requires oxygen to break
down glucose into carbon dioxide, water, and energy. For this process to
occur, oxygen is required by the plant. The cells in the green parts of the
plants perform photosynthesis during the day by using carbon dioxide in the
atmosphere to produce glucose and oxygen. This provides the green parts of
the plant with the necessary oxygen for aerobic cell respiration. However, the
roots in the soil do not carry out this process because of the lack of sunlight,
therefore they cannot produce the required amounts of oxygen themselves
and must be provided with enough of it to perform aerobic cell respiration to
survive. (3)
The summers in Latvia are very unpredictable, and the temperatures in June
vary a lot. During the night the thermometer scale can fall to around 5
degrees Celsius, but in the daytime temperatures tend to rise to 30 degrees
Celsius, with the average temperature in June being about 15 degrees
Celsius. Therefore, the temperatures that I have chosen to vary in my lab are
5, 10, 15, 20, 25 and 30 degrees Celsius. (5)
Hypothesis: ​Higher temperatures increase the energy of oxygen particles in
the water of the soil, causing the motion of the particles and the rate at which
they enter the beetroot cell via simple diffusion to increase. The membrane
becomes more permeable to carry out the process. (4) Considering this
theory, I hypothesize that as the temperature in June increases, the energy of
the oxygen particles in the soil increases, the permeability of the beetroot cell
membrane increases and the rate of simple diffusion increases. Because the
beetroot cells are located in the soil, they have no access to sunlight to carry
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out photosynthesis and produce oxygen themselves. Therefore, higher
temperatures in the beet growing season allow the beetroot cells to take up
more oxygen from the soil at higher temperatures in the summer, therefore
providing the cells with more oxygen to carry out aerobic cell respiration to
survive.
A similar experiment was carried out and recorded by Alex Willifer with the
objective to identify the effect of temperature on the permeability of cell
membranes. (6) The temperatures in his investigation were chosen for
distinct reasons; unlike the ones that are meant to represent temperatures in
the beet growing season in Latvia. Despite the differences, the data collected
is expected to show a similar trend between the temperatures and percent
transmission of light in the betalain pigment solution.
A graph from his experiment plotting the percent transmission of light against
the temperature is adapted to illustrate the hypothesis for my investigation:
Graph adapted from: (6)
The graph visualises the relationship between the independent variable: the
temperature, and the dependent variable: the percent transmission of light in
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the betalain pigment solution. As the temperatures are increased, the percent
transmission of light decreases. The line graph is downward sloping.
Independent variable: ​Temperatures 5, 10, 15, 20, 25 and 30 degrees
Celsius to represent the temperatures in Latvia in the month of June. At
different temperatures the amount of betalain pigment released from the
vacuoles of beetroot cells will change, meaning that the permeability of
beetroot cell membranes is affected, along with energy of oxygen particles
and the rate at which they enter the cell via simple diffusion.
Dependent variable: ​Permeability of the beetroot cell membranes. The data is
obtained using a colorimeter to determine the percent light transmission of
the water samples containing the betalain pigment released from the
beetroot cell vacuoles at different temperatures.
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Control variables
Control variable
What impact would it have on the
investigation if it were not
controlled?
How will the variable be
controlled?
Temperature
(degrees Celsius)
of the individual
water baths.
The energy of oxygen particles in
the samples would vary, causing
the rate of simple diffusion and the
permeability of beetroot cell
membranes to change
A thermometer placed in each of
the measuring cylinders. The
temperatures are checked
throughout the investigation. In
case of a change in the
temperature, immediately regulated
with water in the water bath.
Size of the
beetroot slices (1
cm width, 4 cm
length).
The amount of beetroot cells in the
samples would vary, causing
variation in the amounts of oxygen
absorbed via simple diffusion and
the amount of betalain pigment
released.
A ruler used to measure the length
and width of the beetroot slices.
Precisely cut using a knife.
Amount of water
in the measuring
cylinders (40 mL).
The amount of oxygen particles in
the samples would vary, causing
variation in the amounts of oxygen
absorbed via simple diffusion.
Measured using the 50 mL
measuring cylinders.
The time each
trial is carried out
(30 minutes).
Rate of diffusion is dependent on
the time; different amounts of
oxygen particles would be
absorbed.
A timer is used to make sure that
the trials at each temperature are
carried out in an equal amount of
time.
Materials:
Raw beetroot
Distilled water
Vegetable knife
Kettle
Ruler (± 0.01 cm)
Tray (for damp beets)
Tweezers
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Water bath (large enough to fit in five 50 mL measuring cylinders so that the
water surrounding would reach up to cover ¾ of the cylinders from the
outside)
Five thermometers (± 0.1 degree Celsius)
Ice
Five measuring cylinders (50 mL ± 0.1 mL)
Five beakers (200 mL ± 0.1 mL)
Timer
SpectroVis Colorimeter
Method:
1. Collect all the materials required to perform the experiment.
2. Put on a lab coat.
3. Carefully cut five slices of raw beetroot using the vegetable knife. Do not
place your fingers near the blade. Make sure all individual slices of beetroot
are equal in size (1 cm in width and 4 cm in length).
4. Pour 40 mL of distilled water into five 50 mL measuring cylinders. The five
measuring cylinders correspond to the five trials at the same temperature to
provide reliable data.
5. Fill up a water bath halfway with water. Use ice to keep the temperature at
5 degrees Celsius.
6. Place the measuring cylinders into the water bath.
7. Place the five thermometers into the five measuring cylinders and make
sure the temperature inside the samples reaches 5 degrees Celsius.
8. Place each beetroot slice into the distilled water in the five 50 mL
measuring cylinders.
9. Start the timer and wait exactly thirty minutes.
10. Make sure the temperature in the measuring cylinders remains constant
throughout the experiment.
11. After thirty minutes, remove the measuring cylinders from the water bath.
12. Pour the water content (without the beetroot) of the five 50 mL
measuring cylinders into the five 200 mL beakers.
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13. Make qualitative observations and identify a relationship between the
amount of betalain released from the beetroots and beetroot cell membrane
permeability.
14. Remove the beetroot slices from the measuring cylinders using the
tweezers and place them on the tray. Dispose of them afterwards.
15. Set up the SpectroVis colorimeter. To do that, connect it to a computer.
Open L
​ ogger Pro 3.9​.
16. Follow the instructions to calibrate and set up the SpectroVis colorimeter
for data collection. The instructions can be found in the colorimeter box or
online: source (7) in the bibliography section.
17. Start data collection and record the peak point of percent light
transmission.
18. Repeat step 17. for the samples of water in each beaker.
19. Record the data in a table.
20. Wash the five beakers.
21. Repeat steps 3. – 20. for temperatures 10, 15, 20, 25, 30 degrees Celsius
respectively. For the higher temperatures, instead of using ice to keep it cool,
use the kettle to heat up the water in the water bath. When pouring water
from the kettle, be careful to not spill the hot water onto yourself or other
individuals. Do not carry the water bath with the boiled water around,
perform the experiment in a safe place of the lab.
22. Process the data: calculate the mean values of percent light transmission
for each temperature, the percent error, and the standard deviation.
23. Discuss how the temperature affects the permeability of the beetroot cell
membrane to carry out the absorption of oxygen from the soil via diffusion to
provide healthy growth for the plant.
Method adapted from: (8)
Safety, ethics and environmental impact: ​Use the vegetable knife carefully:
do not put your fingers near the blade to prevent cutting yourself. Pour the
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hot water from the kettle carefully to prevent spilling it on yourself or other
individuals. Do not carry the water baths containing boiled water around,
perform the experiment in a safe place in the lab. Use the tray to place any
wet materials to prevent spilling water and creating a dangerous lab space.
Wear a lab coat to prevent your clothing from betalain, the red pigment of the
beetroot cell vacuoles. Lab space must be cleaned up after performing the
experiment to allow others to use it afterwards.
Qualitative data
Temperature (± 1
degree Celsius)
Observations of the water sample
after the experiment
5
Very pale pink
10
Very pale pink
15
Pink
20
Pink
25
Dark pink
30
Very dark pink
Raw data of percent transmission of light at each temperature
Colorimeter reading (% light transmission)
Temperature (±
1 degree
Celsius)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
5
79.6
83.2
80.3
79.7
78.0
10
72.0
70.3
73.0
68.5
71.4
15
61.9
64.4
61.2
62.2
63.1
20
42.4
44.1
40.5
44.0
40.3
25
32.7
30.7
29.8
33.5
31.9
30
17.6
16.2
16.8
17.2
15.8
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Average percent transmission of light:
Formula:​ (trial 1 + trial 2 + trial 3 + trial 4 + trial 5)/5 = average value %
Example calculation:
5 degrees Celsius: (79.6 + 83.2 + 80.3 + 79.7 + 78.0)/5 = 80.2 %
Percent error:
Formula:​ (|average – most different value|/average) x 100% = percent error
Example calculation:
5 degrees Celsius: (|80.2 – 83.2|)/80.2) x 100% = 3.7 %
Standard deviation:
Formulas:
trial y value – average = d​y​ (y represents number of the trial)
(d​1​2​ + d​2​2​ + d​3​2​ ​+ d​4​2​ ​+ d​5​2​)/5 = variance
√variance = standard deviation
Example calculation:
5 degrees Celsius:
d​1​: 79.6 – 80.2 = -0.6, d​2​: 83.2 – 80.2 = 3.0, d​3​: 80.3 – 80.2 = 0.1, d​4​: 79.7 –
80.2 = -0.5, d​5​: 78.0 – 80.2 = -2.2
Variance = ((-0.6)​2​ + 3.0​2​ + 0.1​2​ + (-0.5)​2​ + (-2.2​2​)/5 = 14.46
Standard deviation = √14.46 = ± 3.8 %
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The average percent transmission of light with percent error and standard
deviation at each temperature
Temperature
(± 1 degree
Celsius)
Colorimeter reading (%
light transmission with
% error)
Colorimeter reading (%
light transmission with
standard deviation)
5
80.2 ± 3.7
80.2 ± 3.8
10
71.0 ± 3.5
71.0 ± 3.4
15
62.6 ± 2.8
62.6 ± 2.4
20
42.3 ± 4.3
42.3 ± 3.7
25
31.7 ± 6.0
31.7 ± 3.0
30
16.7 ± 5.4
16.7 ± 1.5
The data collected in the investigation identifies that as the temperature is
increased, the percent transmission of light passing through the solution of
betalain pigment decreases. The trendline along with the data of the scatter
graph is downward sloping. At lower temperatures, the light passed through
the solution with a relatively low absorption and a higher percent
transmission of light, for example, at 5 degrees Celsius the percent
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transmission of light was on average 80.2 %. As the temperature increased,
the light passed through the solution with a higher absorption and a lower
percent transmission of light, for example, at 30 degrees Celsius the percent
transmission of light was on average 16.7 %. The relationship between
absorbance and percent transmission of light can be presented by the
equation: A = log​10​100/%T, where A is the absorbance and %T the percent
transmittance of light. (9)
The data can also be supported by the qualitative observations of the
experiment (recorded in the qualitative data table section above). The colour
of the betalain pigment solution differed at different temperatures. At lower
temperatures, the water in the samples after thirty minutes was paler pink,
but as the temperatures were increased, the colour was darker. At 5 degrees
Celsius, the colour was a very pale pink, but at 30 degrees Celsius very dark
pink. The percent transmission of light is greater for the pale pink solutions of
betalain pigment at lower temperatures and smaller for the dark pink
solutions at higher temperatures.
The standard deviation identifies how spread the recorded data is from the
average or expected value. It is represented as the error bars on the data
points in the scatter graph. The greatest standard deviation is at 5 degrees
Celsius with the value of 3.8 %. All the other values fall below it. No
anomalies have been detected because the variation in the data is negligible
to the average or expected value. A valid conclusion can be drawn due to the
relatively small errors in the value range between 1.5 % and 3.8 %.
Limitations and weaknesses: ​The concentration of betalain pigment in the
vacuoles of cells can vary with the age of the beets. Throughout the
experiment, several beetroots were used. The vegetables may have been
harvested at different times and may have been of different age, therefore the
concentration of betalain pigment could have varied among the beetroot cell
vacuoles causing the amount of it released to vary.
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Although each beetroot slice was measured to be equal in size, there may
have been variation in the surface area to volume ratio of the slices. The slices
were the same size, but that does not mean that the volume of the cells inside
was equal for all of the slices. This factor could have also caused differences
in the amount of pigment released from the cell vacuoles.
The experiment was carried out throughout the week, therefore the beetroots
were kept in a refrigerator to be used again for the next trials. The change in
conditions such as the temperature might have affected the functions of the
beetroot cells, including the permeability of the membrane, affecting the rate
of diffusion of oxygen particles when placed in the water samples right after
being kept in a significantly colder environment.
Suggested improvements: ​To avoid variance in the concentration of betalain
pigments in beetroot cells due to the age of the vegetables, beetroots that
have been planted, grown and harvested at the same time and conditions
should be used throughout the investigation.
To provide more accurate measurements for the slices of beetroots, therefore
reducing the chance of having variation in the surface area to volume ratio of
the cells, instead of using a knife and measuring the length and width with a
ruler, a size four cork borer should be used to cut identical pieces of the
vegetable.
Throughout the investigation, beetroots should be fresh and kept in the same
conditions to avoid changes in temperature of the environment affect the
permeability of the cell membrane and the rate of diffusion of oxygen
particles before the experiment is carried out in the actual conditions of the
water sample.
Possible extensions of the experiment: ​To extend the experiment, lower and
higher temperatures could be used to determine how the permeability of
beetroot cell membranes would be affected if the temperatures in June
dropped below or rose above the average recorded temperatures in Latvia.
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For the past two years the summers in Latvia have become significantly
warmer. It is assumed to be caused by global warming. Each year the
temperatures
increase in the daytime, however they become very
unpredictable at night; in June it may be recorded to be 30 degrees Celsius in
the day, but the thermometer scale could drop to 0 degrees Celsius or even
below that the following night.
It is important for farmers to know at what nighttime temperatures they have
to provide warmer conditions for the beets to receive the required amounts of
oxygen supply via simple diffusion from the soil to survive. Using the same
method, it could be investigated how lower temperatures that can be below 0
degrees Celsius affect the permeability of the beetroot cell membranes and
the rate of diffusion. The investigation would provide farmers with data that
would allow them to determine the temperature at which their beetroot
plants are at risk of not surviving and be ready to provide the plants with
simulated conditions to increase the temperature, the cell membrane
permeability and rate of diffusion of oxygen particles into the plant roots.
Conclusion: ​The investigation was a simulation for the conditions in June, the
beet growing season in Latvia, with the temperatures falling in the average
range between 5 and 30 degrees Celsius. The temperatures 5, 10, 15, 20, 25
and 30 degrees Celsius were all recorded in the month of June 2018 in Latvia.
(5)
Temperature is one of the most important factors in the permeability of the
cell membrane, as well as the rate of simple diffusion to uptake small
nonpolar molecules such as oxygen. In this investigation, the percent
transmission of light at 5 degrees Celsius was on average 80.2 %, but at 30
degrees Celsius on average 16.7 %. As the temperature increases, the
percent transmission of light in the solution of betalain pigment decreases.
The data collected in this investigation strongly supports the hypothesis. The
shape of the scatter graph visualising the data of this experiment is
analogous to the shape of the line graph visualising the data collected in a
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similar type of investigation performed by Alex Willifer that was stated in the
hypothesis above. (6) Despite the distinct temperatures, the same downward
sloping trend was observed.
From all the quantitative and the qualitative data collected in the investigation
it can be concluded that the temperatures in Latvia have a significant effect
on the permeability of beetroot cell membranes to carry out oxygen
absorption via simple diffusion. At higher temperatures, for example, 30
degrees Celsius the cell membrane becomes more permeable, the oxygen
particles have more energy, therefore moving faster and the rate of simple
diffusion increases. That way the beetroot cells can uptake the necessary
amounts of oxygen from the soil to carry out aerobic cell respiration to
survive. (3)
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References
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https://en.wikipedia.org/wiki/Beetroot#Etymology
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​ ww.biologymad.com/resources/beetroot pigment2.doc
(3) Allott, A., & Mindorff, D. (2014). I​ B Biology ​(2014 ed.). Oxford: Oxford
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(4) J. (2018, April 29). Four Things That Affect Rate of Diffusion. Retrieved
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(6) Willifer, A. (2016, March 11). A Blog about Biology. Retrieved October 24,
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​ ttps://alexwillifersblog.weebly.com/
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(9) Beer's Law - Theoretical Principles. (n.d.). Retrieved September 11, 2018,
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