L1 / EL3 / CL5 / A
AUse apparatus skilfully and safely
L4L4i) Apparatus and materials are handled correctly and safely
and manipulative techniques are used in an appropriate and safe
manner.Personal safety precautions considered
Some care taken to follow safety procedures.
Appropriate techniques attempted.Some elements of risk involved
in using equipment and chemicals is considered
Investigation carried out safely with effort given to
appropriate use of techniquesFull risk assessment in using
equipment and chemicals is considered and safety precautions are
prepared before investigation
Investigation carried out with safety as a priority.
All manipulative techniques used with skillComment by Martin
Mullan:
BProduce and record reliable and valid results
L4/5Comment by Sanngeeta Nadarajan: Comment by Jia He Hong:
Comment by Sanngeeta Nadarajan: Comment by Martin Mullan: Comment
by Sanngeeta Nadarajan: L4/5i) Measurements and observations are
made with precision and recorded in a structured manner; variables
are identified and the validity and reliability of results are
justified.Student follows teacher's plan
Independent and Dependent variables identified.Comment by Martin
Mullan:
Appropriate equipment is used to make measurements over an
inappropriate range
Most measurements are performed with accuracy but the methods
used to acquire these are not justified e.g. measure at eye
level
An appropriate number repeats are planned for but not
completed
A table of results is built but has errors on decimal places
and/or units and is disorganisedStudent follows teacher's plan and
makes attempts to enhance the plan with their own ideas based on
their experience and research.
Appropriately precise equipment is used to make measurements
over an appropriate range
All measurements are performed with accuracy and the methods
used to acquire these are justified e.g. measure at eye level
An appropriate number repeats are planned for and completed
A detailed, neat and complete table of results is built but has
errors on decimal places and/or units
Student refers to published data to support their conclusions
and therefore enhance the validity of their findingsStudent
generates a plan with their own ideas based on their experience and
research. Controls and/or placebos are considered and the use of
blind and double blind trials are evaluated.
Appropriately precise equipment is justified in its use and is
used to make measurements over an appropriate range
A detailed, neat and complete table of results is built
Student conducts research into published data to support their
conclusions and therefore enhance the validity of their findings
(all references annotated correctly)
L4/5L4ii) Possible systematic errors and random errors in
generating results are identified and explained.Student identifies
a possible confounding variable and describes how it's effect can
be reducedAll possible 'confounding' variables are identified and
efforts described to reduce their effects (Random errors)Systematic
errors (e.g. zero error) are identified and how these can be
reduced considered
CPresent and analyse data
L4L3Comment by Jia He Hong: Comment by Martin Mullan:
i) Use appropriate methods to analyse results, present data and
identify trends, patterns and/or observations.Inappropriate or
incomplete graph drawn
Student makes use of: descriptive statistics e.g. mean
Student identifies relationships in graphic representation to
identify patterns and relationships (eg correlation and cause)
Student uses the observed data to support their
statementsComment by Martin Mullan: Appropriate (bar chart for
categoric data, histogram, line graph for continuous data) and
complete graph (SLAPU'd) drawn
Basic subtraction mathematical operations are used to support
observationsStudent makes use of: descriptive statistics (mean,
mode and median, error bars, standard deviation identification of
outliers and range)
Mathematical operations are used to support observations e.g. %
change and % difference
L4Comment by Sanngeeta Nadarajan: L4/5ii) Any apparent anomalies
and inconsistencies are described, the methodology is evaluated and
suggestions are made to improve or further the work of the
investigation.Validity, Accuracy, Precision, Reliability (VAPR) are
not fully evaluated or are incomplete/confused.
Student identifies outliers and/or anomalies but is unable to
explain why they occur or how to improve the technique to reduce
them next timeStudent attempts to evaluate the validity of
inferences made from data in terms of the methods, techniques and
processes (Validity, Accuracy, Precision, Reliability - VAPR) used
to collect and analyse the data
Student attempts to explain why there is a lot of variability in
their repeated measurements AND/OR identifies and attempts to
explain outliers and anomalies in their measurements in an effort
to reduce their effects in the futureStudent fully evaluates the
validity of inferences made from data in terms of the methods,
techniques and processes (Validity, Accuracy, Precision,
Reliability - VAPR) used to collect and analyse the data,
recognising any systematic or random errors present or conflicting
evidence.
Student explains why there is a lot of variability in their
repeated measurements and explains outliers and anomalies in their
measurements in an effort to reduce their effects in the future
Student suggests extensions to the current investigation to
acquire more data in similar contexts to support their conclusions
e.g. effect of caffeine on the number of leg twitches in brine
shrimp
Create a full write-up using the resources you have been given.
Include: introduction and science, [Theory upon which the
investigation is based] hypothesis, [A testable statement]
equipment, [A full list with justification for use] plan, [Step by
step guide based on CORMS] safety, [All equipment, techniques and
chemicals are analysed for risk] table of results, [neat, organised
and with appropriate dps] graph (table and graph should be
hand-drawn and uploaded into your GDrive folder - Embed OR create a
link to them in your write-up doc), [SLAPU, line drawn with ruler
dot-to-dot] analysis, [A written description of the data showing
findings and comparisons between treatments] discussion, [An
explanation for the findings in the analysis based on theory]
conclusion,[A summative statement of the findings in relation to
the hypothesis] evaluation, [A review of the Validity, Accuracy,
Precision and Reliability of the techniques and plan used]
references/bibliography [laid out as per the research requirements]
Self Assessment [Each section scored with a justification] Peer
Assessment [Each section scored with a justification]
Use the rubric to remind yourself of what needs to be
included.
Self assess yourself against the rubric and include the score at
the end of your writeup. Use the commenting features to identify
your point allocation. Ask to share in a partner to allow them to
peer assess.
Investigating the effect of temperature and alcohol on the
membrane permeability of beetroot cells
Introduction: Comment by Martin Mullan:
This experiment is aimed to investigate the effect of
temperature on the permeability of the cell membrane in plant
cells. (As the cell membrane in the plant cell roughly mimics those
of the animal cell, we can also use this experiment to investigate
how temperature and alcohol concentration affects our cell
membrane. However, this statement would not be 100% accurate as the
plant cell also has a cellulose cell wall covering its cell
membrane which would mean that the temperature and the alcohol
would have to break the cell wall first before reaching the cell
membrane which differs to our animal cells as we do not have a
cellulose cell wall protecting our plasma membrane.) Comment by Jia
He Hong: Comment by Sanngeeta Nadarajan: We are using Beet Root
cells as out plant cells due to the fact that the beet root cells
contain betalain pigments, which give it its colouring. Therefore,
as the membrane becomes more permeable, the Betalain pigment, found
in the vacuole, would escape the cell and enter the solution, and
as they are water soluble and would dissolve in the water, we can
then measure how concentrated the solution is, of the colour red,
and come to the conclusion of whether one solution is more of the
colour red than the other and therefore, whether one solution has
more Betalain pigments in them than the other. As you cut the beet
root, or when the membrane of the beet root is damaged, the
Betalain pigment, from inside the cell, would escape the cell as
there are spaces between the membrane that the pigment can move
through. Also, this can also be considered to be a form of
diffusion as there is a higher concentration of Betalain pigment in
the cell and a lower concentration of pigment in the solution (so
the other side of the membrane). This means that the pigment would
move down the concentration gradient, from inside the cell to the
outside of the cell, to reach equilibrium. However, the
permeability of the membrane also plays a huge part in diffusion as
the pigment might try to reach equilibrium, but wouldnt be able to
do so if the membrane isnt as permeable and the pigments would not
be able to move out in enough time as we have a time limit.Comment
by Martin Mullan: Membranes are made up of 2 main molecules, lipids
and proteins. As you increase the temperature of the solution that
has the beet root immersed in it, you are supplying more heat
energy to the lipids in the cell membrane. As you supply more heat
energy, the phospholipids gain more kinetic energy and they vibrate
more rapidly. As they vibrate more, the particles from inside of
the cell membrane is able to move out through the spaces. Also, as
you supply more heat, the proteins get denatured due to the heat.
This will then cause the cell membranes to break apart as there are
integral proteins that are submersed in between the phospholipid
bilayer. As the protein denatures, it is easier for the pigments to
escape the cell membrane. As you measure how concentrated a
solution is, you can measure the level of disruption caused by that
particular temperature. Comment by Martin Mullan: Comment by Jia He
Hong: Comment by Sanngeeta Nadarajan: Comment by Martin Mullan:
There were no ethical issues when conducting this experiment as
it was based only on plants and no animals or humans were harmed
during the process of the experiment.
Hypothesis
The higher the temperature of the solution, the more
concentrated the solution would be after the experiment (i.e. it
would be a more deeper colour). This means that the membrane would
be more permeable in a higher temperature. Also, the higher the
concentration of alcohol used in the solution, the more
concentrated the solution would be after the experiment (it would
be a more deeper colour). This means that the membrane would be
disrupted, which means that more pigment would escape and make the
solution more concentrated.
Equipment
Colorimeter - For this experiment, we will be using the
Colorimeter to determine the colour concentration of substances.
The more concentrated a substance is, the deeper the colour of the
substance is like, and the Colorimeter measures the depth of colour
in the substance, and therefore, gives us a measure of the
concentration of the substance. The colorimeter has a light source
in it, that can shine the colour red, green and blue. By using the
absorbance calculator in the colorimeter, you can measure how much
of light goes through the solution. According to Beer-Lamberts law,
it states that the absorption of light through the medium is
directly proportional to the concentration of colour in that
substance. The more light is transmitted, the less light is
absorbed. The more coloured a solution is, the lesser the light
would be transmitted through the solution and the more the light
would be absorbed. We used the colorimeter as there would have been
no other device that can accurately measure how concentrated a
solution is of the particular colour. (In this case, it would be
the red colour of the Betalain Pigment) Comment by Martin
Mullan:
Cuvette - We had placed the solution from the test tubes into
the cuvettes. The cuvette was then put into the colorimeter and we
had measured the light absorbance of the solution. The cuvette was
appropriate because it was a part of the colorimeter and had fit
perfectly into the colorimeter and also because it was transparent,
which allowed light through it. Also, ensure that, when placing the
cuvette, the side that does not have any marks in it and is a plain
empty side is placed directly infront of the light source to allow
the light source to penetrate as efficiently as possible. Comment
by Jia He Hong: Comment by Sanngeeta Nadarajan: Comment by Martin
Mullan: Comment by Martin Mullan:
Cork borer - This equipment was used to bore the beet root into
identical cylinders. Even though they all had different lengths,
the width of the beet root would have been the same and therefore,
the validity of the experiment, by making sure the surface area of
the beet roots were as similar as possible, would have been
secured. This, therefore, would have made our results reliable as
one of the variables was kept the same. The borer was also used to
speed up the process of the experiment, rather than cutting the
beet root with a knife and having to make sure that they are the
same width, which would have been extremely time consuming.
Measuring cylinder - We had used a 25 ml Measuring cylinder when
measuring the volume of water to be poured into the test tube. We
had used a 25 ml Measuring cylinder as we were measuring 15 ml of
liquid. Using the appropriate measuring cylinder (not a bigger or a
smaller one) was to ensure that, when measuring the solution to be
poured into the test tube, it was as accurate and as precise as
possible and to prevent any reading errors that could occur with a
larger measuring cylinder (such as a 50ml measuring cylinder) as
the scales would usually be bigger on a larger measuring cylinder.
Comment by Jia He Hong: Comment by Sanngeeta Nadarajan: Comment by
Martin Mullan:
Knife A knife was used to cut the beetroot cylinders into small
disc shapes. This is to increase the surface area of the beet root,
to ensure that diffusion occurs at its maximum possible rate. We
could have left the beet root as a cylinder but it would take a
long time for diffusion to occur thoroughly and we didn't have a
very long time to complete this experiment. Even though diffusion
probably didn't occur thoroughly in this experiment either, it had
a faster rate than if we were to have left it in its cylindrical
shape. Besides this, as we cut the beet root into discs, there was
a large part of the beetroot that was exposed to the solution and
therefore the temperature, and therefore the effect of temperature
on the cell membranes of plant cells can be thoroughly explored.
However, because we used a knife to cut the beet root into discs,
the precision and the accuracy of the length of the beet root was
compromised, therefore affecting the reliability of our results.
This is because when we cut the beet root with the knife, even
though they look similar in length, the length isn't the same and
this means that each disc has a different volume, and different
surface area, and therefore the surface area to volume ratio is
different for each beet root disc, and this affects the rate of
diffusion.Comment by Jia He Hong: To improve the precision and
accuracy of the discs, we could use an equipment like a Mandoline,
which would cut the beet root to the same length and therefore,
improving the reliability of our experiment.Comment by Jia He Hong:
Comment by Sanngeeta Nadarajan: Comment by Sanngeeta Nadarajan:
Comment by Sanngeeta Nadarajan: Comment by Martin Mullan: Comment
by Martin Mullan:
Test tube We used a test tube for the experiment instead of
using any other type of apparatus because the it is crucial that
the surface area of the apparatus also stays the same as this could
also affect the rate of diffusion. It is also easier as we can put
the test tubes in a test tube rack and place them in the water
bath.
Mounted needle It was very important for us to use the mounted
needle to make sure that the beet root discs aren't touching each
other. This was done by mounting the beet root onto the needle of
the mounted needle, and making sure there was spaces between the
beet root discs. This is to ensure that the surface area is
maintained , instead of decreasing it if the discs were to touch
each other. The higher the surface area, the higher the rate of
diffusion as more of the cells are exposed to the solution, and
thus the temperature.Comment by Martin Mullan:
Test Tube rack - The rack is used when the test tubes are placed
onto the test tube rack and is placed in the water bath. This is to
prevent from carelessly placing the test tubes in the water bath or
prevents us from holding the test tubes in the water bath for a
very long time. Also, it prevents the test tubes from touching the
bottom of the water bath, which is a piece of metal and it gets hot
easily and might break the test tubes or affect the temperature of
the solution in the test tubes by making them higher, and
therefore, affecting the reliability of our results. Comment by
Martin Mullan:
Thermometer- The thermometer was used to measure the temperature
of the solution in the test tubes. The thermometer was used because
even though we had set the water baths to specific temperatures, we
had placed the test tube rack into the water baths at a different
time and this affected the rate that the water got heated up at.
Ideally, we had wanted the temperatures for our solutions to
increase by 10 degree celcius, with 10 to 50 degree celcius.
However, as some test tubes didnt heat up to the temperatures we
wanted them to be at, due to time constraints, we had measured the
temperature of the solution in the test tubes instead. However, the
test tubes that had heated up to the temperature we wanted them to
be at, we had also measured their temperature before inserting the
beetroots, to ensure that we are inserting them at the correct
temperature and if it wasnt at the right temperature, to see the
effect of the temperature on the cell membrane at that particular
temperature.
Eye goggles - This is used to protect our eyes during the
experiment and is used as a safety measure to ensure no liquid
enters our eyes or as we are cutting the beet root, it might be
squishy and the liquid might splash into our eyes.
Plan
1. Cut your beetroot in half and peel away the skin. using the
cork borer, remove 3 cylinders of beet roots. 2. Using a ruler and
scalpel, slice the cylinder into 2 mm thick discs. 3. Place the
slices into a beaker of cold water until needed. It was placed into
cold water as the coldness of the water reduces the kinetic energy
of the particles in the cell and outside of the cell, and thus
decreases the rate of diffusion and prevent them from already
diffusing the pigments out as we havent started testing them with
our experimented temperature yet. Also, it could be to prevent the
beet root discs from wilting, if left out in the open, which might
affect the rate of diffusion as the more wilted the disc is, the
lesser the rate of diffusion as the fact that it has wilted could
mean that the membranes have already been disrupted, and therefore
the actual effect of the temperatures on the cell membranes are not
accurate. 4. Prepare 3 test tubes with the same volume of water to
ensure that the experiment was repeated, to improve the reliability
of the experiment. 5. Place test-tubes containing the same volume
of water of 15 ml into each of the available water baths. Leave for
as long as needed to raise the temperature of the solution to your
desired temperature. However, be aware of the time. Ensure that the
same volume of water is poured into the test tube, to ensure that
the validity of the experiment is insured as if the volume of water
is increased, the surface area of the cell membrane is exposed to a
larger volume of water, and that increases the rate of diffusion.
The opposite would occur with a decreased amount of water, as if
the water was too little, then the surface of the cell membrane
wouldnt be exposed to much water. 6. Put 5 discs on a mounted
needle/pin and rinse until water runs clear. Rinse the beet root to
ensure that there arent any excess pigment on it that may cause an
incorrect reading of the absorbance level in the colorimeter for
the results. This is because the excess pigment would have resulted
from the cutting of the beetroot instead of the diffusion process
itself and this would have affected the reliability of our results.
Comment by Martin Mullan: 7. Place the mounted beetroot in a test
tube. Make a note of the temperature of the solution in the test
tube. 8. Place the test tube into a test tube rack and place the
test tube rack into the water baths for 10 minutes. You keep it in
for 10 minutes to allow diffusion to happen. 9. Remove the test
tube after 10 minutes and leave to stand for 5 minutes. This is to
allow the temperature of the solution to cool down and as the
temperature cools down, the rate of diffusion slows down as well.
10. After 5 minutes, remove the beetroot from the test tube and
measure the amount of light that the coloured water absorbs using
the cuvettes and a colorimeter. 11. Repeat steps 1-9 with the other
temperatures of water baths.
Safety
Make sure you wear safety goggles during the experiment to
prevent any liquids splashing into your eyes. Also, make sure that,
when using the cork borer, you cut away from your hands. Also, make
sure that precaution is taken when using the scalpel and ensure
that you use it safe enough to not cut yourself. When handling
liquid with temperatures, take precaution needed (such as using
tongs) to prevent scalding of hands. Also, when handling liquid,
ensure that the liquid doesnt spill anywhere that might cause
someone to trip and fall. When handling the water bath, make sure
that you do not place your hand inside to ensure that scalding does
not occur, in case the temperature of the water is hot. Also, when
placing the beet root on the mounted needle, ensure that the needle
is not facing your hand and it is facing away. Also, be careful of
your fingers when mounting the beet root onto the needle and try to
keep them as far away from the needle as possible. Also, make sure
that you wear gloves when handling the beet root, as the pigment
would stain your fingers strongly.
Table of Results Comment by Martin Mullan: Comment by Sanngeeta
Nadarajan:
Graph
Comment by Jia He Hong: Comment by Sanngeeta Nadarajan: Comment
by Martin Mullan: Comment by Sanngeeta Nadarajan:
From the graph, that as the temperature increased, the
absorbance of light in the colorimeter had also increased. This is
because we can see that as the it progresses in the X-Axis, the
values in the Y Axis also increase. However, this is not in a
constant rate as the points are not in a straight line. from the
values of 50 degree celcius to 58 degree celcius, there is a
massive jump in the absorbance value. And this means that the
solution at 58 degree celcius is more concentrated in colour than
the 50 degree celcius. However, this is massively contrasting to
the values from 42 degree celcius to the 50 degree celcius and the
values from 50 degree celcius to 58 degree celcius. We, however, do
not have an experimented temperature between 8 degree celcius and
40 degree celcius so we do not know if it is an actual straight
line and if the value is rising at a constant rate. Comment by Jia
He Hong: Comment by Martin Mullan: Comment by Martin Mullan: I had
also used error bars in my graph, which shows the smallest result
and the highest result of that particular temperature. However, as
we have only plotted the averages of the values that we got from
the experiments, the error bars tell us that the actual value of
the result could be in between this bar and indicate the varibility
of the data. They offer a standard deviation and it shows how
accurate our data is. The smaller the error bars are, the more
reliableour data are. Also, if the error bars do not overlap, that
would mean that the data is statistically significant. However, if
the error bars do overlap, that could mean that the absorbance
values could possibly mean that the data is not statistically
significant and there could be an error when performing the
experiment and you cannot possibly tell that the actual value of
the absorbance at that particular temperature, as the fact that the
error bars overlap mean that the actual absorbance value of that
temperature could be in between the overlap. Also, the wider the
range of the error bars, the more the data is not precise because
there is a larger gap between the highest value and the lowest
value and the actual value could be anywhere between it. Comment by
Martin Mullan:
Discussion
From the results, the temperature increased, the absorbance of
the light in the solution had also increased. This means that there
are more pigments in the solution, which is why the value of
absorbance is high. The higher the temperature gets, the more
kinetic energy is supplied to the particles in the membrane and
this makes them vibrate more. As the particles vibrate more, they
move and this means that there is space in between the particles
(the phospholipid bilayer and the proteins), and this allows the
pigments to leak out and enter the solution. As the pigment is
insoluble in lipids, as it comes out and enters the solution, it
dissolves in the solution, colouring it. This is because the
pigment is polar and can be broken apart in the water due to the
dipole nature of water. Also, as the temperature gets higher, the
proteins get denatured and this allows the pigments to also move
between the proteins and through the now disrupted membrane and
enter the solution through diffusion. Diffusion occurs as the
solution in the test tube contains a low concentration of Betalain
pigments and the inside of the cell membrane contains a high
concentration of Betalain Pigment cells and in order to reach
equilibrium, the Betalain pigments moves out and enters the
solution. Also, as the temperature increased, the pigments would
also get more kinetic energy supplied from the heat energy and this
means that the pigments would also move faster and thus, enter the
solution more quickly. As the membranes get disrupted, that is why
the cell isnt turgid anymore as the water from the cells isnt
applying pressure on the wall of the cell anymore and instead has
entered the solution and is why the plant looks flaccid and soft
instead. If the temperature is too cold, the cytoplasm in the cell
would have frozen and as they freeze, the space between the water
molecules would have expanded and the cells would burst, thus
allowing the pigments to escape. However, we did not experiment
with a solution that had a temperature that was cold enough for
that to occur. In the results, we can see that there is a big jump
at 50 degree celcius to 58 degree celcius. This was at a point
where the jump was between 0.344 and 1.018. As the error bars dont
overlap, we could assume that the phospholipids gain more energy
and move faster and the proteins get denatured at a much faster and
more significant rate that it the constant gradient is very steep,
which suggests that the rate of damage was fast.
Conclusion
As conclusion, we can see the absorbance of colour increase as
the temperature increased. This tells us that the higher the
temperature, the more disrupted the membranes get and the more
denatured the proteins get, and therefore, the more the pigment was
able to leak out. This is due to the fact that as temperatures
increase, the particles gain more kinetic energy and they vibrate
faster and therefore, create spaces between the phospholipids,
which allows the pigments to move out. It is also because the
proteins get denatured at a higher temperature, which also allows
the pigments to move out as there is now space between the integral
proteins and the phospholipids. Comment by Jia He Hong: Comment by
Jia He Hong: Comment by Martin Mullan:
Evaluation
Even though the results had correlated with other beetroot
experiments that I had researched, we had committed an error during
the experiment that could have affected our experiment strongly. As
we were cutting the beetroot cylinders into small discs, we did not
use a proper device, like a mandoline, to cut the discs. Instead,
we had used a knife to cut the beet root and despite most of them
being of similar length, they were not the same length and
therefore, the accuracy and the precision was affected, which, in
turn, had affected the reliability and the validity of our results.
This was because the larger the disc, the larger the volume, the
smaller the surface area to volume ratio, and therefore, the rate
of diffusion would decrease.
A possible systematic error that could have occurred is if we
hadnt calibrated the colorimeter before using it. To calibrate the
colorimeter, we had poured some distilled water into the cuvette
and placed it in the colorimeter and pressed the calibrate button,
where the absorbance would be written as 0.00. If we hadnt
calibrated the colorimeter, the value that we would have seen
during the experiment would have been false and inaccurate and
thus, affect the reliability and the validity of our results.
Comment by Martin Mullan:
There were a lot of variability between our repeated
measurements as not all of the water in the specific test tubes had
risen up to the temperature we had predicted them to be at as, due
to time constraints, we had only measured the temperature of one
test tube and assumed that it had the same temperature as the other
test tubes. However, by taking the time to measure all 3 of the
test tubes could also cause some variability in our results as when
we are measuring the temperature of water in one test tube, the
temperature of the other test tubes could have risen or dropped,
which means that they arent the same temperatures as when they were
measured. Comment by Martin Mullan:
In our experiment, we had to make sure that we kept the surface
area of the beet root the same (as the smaller the surface area to
volume ratio, the quicker the rate of diffusion), the type of beet
root (as different beet roots might have a different effect to
temperature, especially if theyre from different countries) and the
time in which the beet root was left out for (if the beet root was
left out longer, due to diffusion and evaporation or even the
temperature of the room, the beet roots themselves would have
wilted. This would mean that the membranes have been disrupted and
the water, including the pigment, has escaped from the cell, which
gives it its wilting effect.) Also, the number of beet root discs
that are placed on each needle has to also be the same as the more
discs there are, the greater the rate of diffusion, which would
make the colour of the solution more concentrated and affect the
validity and reliability of our results. Besides that, the amount
of time that we leave the beet roots in the test tube for, has to
also remain the same as the longer the beetroot discs are exposed
to the temperature, the more the rate of diffusion occurs as the
more the membrane gets affected. Comment by Jia He Hong: Comment by
Martin Mullan:
Unfortunately, as mentioned above, in this experiment, we had
not experimented with any values between 42 degree celcius and 8
degree celcius. Ideally, we would have liked to measure
temperatures that have a 10 degree celcius interval to see the
effect of the temperature on the cell membrane in a gradual affect.
However, the fact that we were unable to do so, due to the water
bath not heating up to the right temperatures, would affect our
results in the sense that we do not know if there are any
significant changes between the values and affects the reliability
of our results as we do not have another result to coordinate with
the conclusion. Also, due to the fact that we did not have enough
time to let the temperature of the solution to increase to the
temperature we wanted them to be at, we had a massive gap between 8
degree celcius and 42 degree celcius but only had an 8 degree
celcius difference between the other results. This would affect the
validity of our results as we did not measure the effect that the
other temperatures had on the cell membrane and instead,
experimented on values that are very close to each other and that
increase but only by a small amount and there is no significant
change, which we would have predicted to happen.
According to
http://www.nuffieldfoundation.org/practical-biology/investigating-effect-temperature-plant-cell-membranes
, they also had results that were similar to us, although they had
experimented with temperature values that are different but still
similar to our experimented temperatures. They had also measured
their values as a transmission value, instead of absorbance values.
This would mean that they were measuring the amount of light that
went through the solution, instead of the value of absorbance of
the solution. The higher the absorbance value, the lesser the
transmission value. This is because as the solution is more
concentrated, the more light is absorbed through it and the higher
the absorbance value. This also means that the more concentrated a
solution is, lesser light is transmitted through the solution,
which is why the value is low. Therefore, their results still
correlate with my results as we can see that the higher the
temperature, the lesser the transmission value. This would mean
that the absorbance is high due to the fact that the solution is
more concentrated due to the fact that membranes were disrupted at
a high rate. Comment by Martin Mullan: Comment by Aisling Murray:
Comment by Martin Mullan: Comment by Sanngeeta Nadarajan: Comment
by Sanngeeta Nadarajan:
As an extension, we could have experimented with values that
were close to 0 degree celcius or even below it. Theoretically, as
the temperature becomes very low, the cytoplasm, which is mainly
made up of water, would freeze and in the process, the water
molecules would get further away from each other as they form a
lattice, which would mean that it expands and becomes less dense.
As the cytoplasm expands, the cells would burst open as the
cytoplasm applies pressure onto the cell membrane and therefore,
the cell membrane is disrupted and the pigment leaks out.
Therefore, as the temperature goes really low, the solution becomes
more concentrated as the membranes are more disrupted. Comment by
Martin Mullan:
Reference/Bibliography
http://www.nuffieldfoundation.org/practical-biology/investigating-effect-temperature-plant-cell-membranes
http://egret.psychol.cam.ac.uk/statistics/local_copies_of_sources_Cardinal_and_Aitken_ANOVA/errorbars.htm
Rubric rating submitted on: Tue Nov 04 2014 03:36:49 GMT-0500
(EST) by [email protected]
AUse apparatus skilfully and safely
i) Apparatus and materials are handled correctly and safely and
manipulative techniques are used in an appropriate and safe manner
Your score: 4Personal safety precautions considered
Some care taken to follow safety procedures.
Appropriate techniques attempted.Some elements of risk involved
in using equipment and chemicals is considered
Personal safety precautions considered
Investigation carried out safely with effort given to
appropriate use of techniquesFull risk assessment in using
equipment and chemicals is considered and safety precautions are
prepared before investigation
Investigation carried out with safety as a priority.
All manipulative techniques used with skill
AUse apparatus skilfully and safely
ii) The practical work is carried out in an organised,
methodical and safe manner, with due consideration of the
well-being of living organisms and the environment. Your score: 0A
brief comment on the ethical issues involved in the context of the
investigationMost of the ethical issues involved in the context of
the investigation are considered and evaluatedFull consideration of
the ethical issues involved in the techniques with regards to
humans and animals.
E.g. treatment of daphnia in caffeine investigation OR the
social, moral and economic implications of using the antimicrobial
properties of plants
B Produce and record reliable and valid results
i) Measurements and observations are made with precision and
recorded in a structured manner; variables are identified and the
validity and reliability of results are justified. Your score:
4.5Student follows teacher's plan
Independent and Dependent variables identified.
Appropriate equipment is used to make measurements over an
inappropriate range
Most measurements are performed with accuracy but the methods
used to acquire these are not justified e.g. measure at eye
level
An appropriate number repeats are planned for but not
completed
A table of results is built but has errors on decimal places
and/or units and is disorganisedStudent follows teacher's plan and
makes attempts to enhance the plan with their own ideas based on
their experience and research.
Independent and Dependent variables identified.
Appropriately precise equipment is used to make measurements
over an appropriate range
All measurements are performed with accuracy and the methods
used to acquire these are justified e.g. measure at eye level
An appropriate number repeats are planned for and completed
A detailed, neat and complete table of results is built but has
errors on decimal places and/or units
Student refers to published data to support their conclusions
and therefore enhance the validity of their findingsStudent
generates a plan with their own ideas based on their experience and
research. Controls and/or placebos are considered and the use of
blind and double blind trials are evaluated.
Independent and Dependent variables identified.
Appropriately precise equipment is justified in its use and is
used to make measurements over an appropriate range
All measurements are performed with accuracy and the methods
used to acquire these are justified e.g. measure at eye level
An appropriate number repeats are planned for and completed
A detailed, neat and complete table of results is built
Student conducts research into published data to support their
conclusions and therefore enhance the validity of their findings
(all references annotated correctly)
B Produce and record reliable and valid results
ii) Possible systematic errors and random errors in generating
results are identified and explained. Your score: 5Student
identifies a possible confounding variable and describes how it's
effect can be reducedAll possible 'confounding' variables are
identified and efforts described to reduce their effects (Random
errors)All possible 'confounding' variables are identified and
efforts described to reduce their effects (Random errors)
Systematic errors (e.g. zero error) are identified and how these
can be reduced considered
CPresent and analyse data
i) Use appropriate methods to analyse results, present data and
identify trends, patterns and/or observations. Your score:
3Inappropriate or incomplete graph drawn
Student makes use of: descriptive statistics e.g. mean
Student identifies relationships in graphic representation to
identify patterns and relationships (eg correlation and cause)
Student uses the observed data to support their
statementsAppropriate (bar chart for categoric data, histogram,
line graph for continuous data) and complete graph (SLAPU'd)
drawn
Student makes use of: descriptive statistics e.g. mean
Student identifies relationships in graphic representation to
identify patterns and relationships (eg correlation and cause)
Basic subtraction mathematical operations are used to support
observationsAppropriate and complete graph drawn
Student makes use of: descriptive statistics (mean, mode and
median, error bars, standard deviation identification of outliers
and range)
Student identifies relationships in graphic representation to
identify patterns and relationships (eg correlation and cause)
Mathematical operations are used to support observations e.g. %
change and % difference
CPresent and analyse data
ii) Any apparent anomalies and inconsistencies are described,
the methodology is evaluated and suggestions are made to improve or
further the work of the investigation. Your score: 4Validity,
Accuracy, Precision, Reliability (VAPR) are not fully evaluated or
are incomplete/confused.
Student identifies outliers and/or anomalies but is unable to
explain why they occur or how to improve the technique to reduce
them next timeStudent attempts to evaluate the validity of
inferences made from data in terms of the methods, techniques and
processes (Validity, Accuracy, Precision, Reliability - VAPR) used
to collect and analyse the data
Student attempts to explain why there is a lot of variability in
their repeated measurements AND/OR identifies and attempts to
explain outliers and anomalies in their measurements in an effort
to reduce their effects in the futureStudent fully evaluates the
validity of inferences made from data in terms of the methods,
techniques and processes (Validity, Accuracy, Precision,
Reliability - VAPR) used to collect and analyse the data,
recognising any systematic or random errors present or conflicting
evidence.
Student explains why there is a lot of variability in their
repeated measurements and explains outliers and anomalies in their
measurements in an effort to reduce their effects in the future
Student suggests extensions to the current investigation to
acquire more data in similar contexts to support their conclusions
e.g. effect of caffeine on the number of leg twitches in brine
shrimp
Self-assessment Your score: 5Basic pointsSome points are
thoroughly evaluated and relate to the rubricThorough consideration
of why the point has been awarded or not
Peer-assessment Your score: 5Basic pointsSome points are
thoroughly evaluated and relate to the rubricThorough consideration
of why the point has been awarded or not
Comments:20.5/25Excellent work Sanngeeta. Your theory and
research are very good. The thoroughness of the planning is awesome
and you evaluate well.You have to focus on the analysis. What is
the point of all the great preparation if you don't analyse
properly. No maths...no differences...George pointed it out too
;-PAnalysing graphs WILL come up in your exam...I suggest to fix
this.Cheers, Mullan
