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Biology SL - Internal Assessment (grade 7)
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IA awarded a grade of 7 in the IB. Includes all parts needed.
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IBDP Biology SL - Internal Assessment1. EXPLORATION
1.2 Introduction:
This investigation is relevant to me because I used to be vegan and was potentially
diabetic. I had a rough diet change and most of my salads had vinegar and beetroot (B.vulgaris)
included. Vinegar is known to aid in decreasing blood sugar spikes after carb-heavy meals
(Gunnars and Spritzler) and beetroots are high in fiber, manganese, potassium, iron, and vitamin
C, among other minerals which are linked to a variety of health advantages, including enhanced
blood flow, decreased blood pressure, and improved athletic performance (Bjarnadottir and
Coyle). Having eaten this salad several times in different ways, I have realized that the vinegar
often turns pigmented due to the beetroot and makes the meal visually unappetising. However,
each vinegar type turned a different shade of red. Learning about membrane permeability in
biology, I have decided to investigate the loss of pigment in beetroot in different vinegars in
respect to the topics learnt.
Beetroot, Beta vulgaris, has the characteristic of betalains pigment found in the stem
tuber. Because these pigments are often found within the vacuole of intact beetroot cells, they are
a valuable sign of membrane fluidity (“Investigating the effect of temperature on plant cell
membranes”). Increased membrane fluidity causes pigment to seep out of the cell, and the
amount of pigment may be easily detected with a colorimeter.
A colorimeter will be used, it is a tool used in colorimetry to gauge a solution's ability to
absorb various light wavelengths. By measuring the values of red, green, and blue, a colorimeter,
which "sees" color similarly to the human eye, may pinpoint where a color is situated in the color
space. (“What Is Color Measurement?”). These will give numerical values of the absorbance of a
certain color, in this experiment violet (430 nm). Hence, Sandra Dias’ research will be used to
convert the violet absorbance value into betaxanthins (pigment in beetroot). Dias’s method
includes the violet absorbance and dilution factor. And using ANOVA, the significance in
absorbance of different environments can be observed. Using sample data, the ANOVA test
determines whether a difference between the averages of two or more groups is meaningful.
1.3 Research Question:
Evaluated through a colorimeter (mg/L), how does five different vinegars (white, white wine,
rice, white balsamic and apple cider vinegar) affect the membrane permeability causing the loss
of pigment in 4cm Beta vulgaris (beetroot) cylinders, measured as betaxanthins equivalent?
1.4 Hypothesis:
H1: If the different vinegars have different effects on the permeability of the beetroot cylinders,
they will give different absorbance after being mixed with the beetroot for a fixed period of time.
This is because vinegars with higher values of acetic acid will damage the cell membrane of the
beetroot more and cause more leakage of the pigments.
, H0: If there is no change in permeability of the beetroot cells when different vinegars are used,
then there will not be any significant difference between them. This is because the membrane
will stay the same with all vinegars and the pigment will not leak out.
1.5 Variables:
Table 1: Variables Selected for this Experiment
Units Range
Independent Variable Types of N/A (not 5
vinegar (No applicable)
Name white
vinegar,
President’s
Choice white
wine vinegar,
Krinos white
balsamic
vinegar,
Bragg apple
cider vinegar
(5% acetic acid)
Dependent Variable Change in Wavelength (nm) 430 nm and
absorbance 635 nm
measured by
colorimeter
Controlled Variables Units Possible Effects How the variable will be
controlled
The volume of each type Milliliter A different amount of solution The graduated cylinder will be
of vinegar in the test tubes (± 0. 5𝑚𝑙) in each test tube will not allow used carefully pouring in the
for fair data to be tested. The solution softly so as to not make
ratio of surface area to volume mistakes when measuring the
will be different which will liquid.
have different speeds of
osmosis.
Size of beetroot cylinders Millimeters The size of the beetroot will This will be controlled through a
(± 0. 5𝑚𝑚) determine the rate of pigment ruler (measured 4cm) and a cork
loss. If the size of each beetroot borer (width 0.7cm). The same
strip is different, then the cork borer will be used with all
, results will not be fair since the the trials.
pigment for each trial will be
imbalanced.
Amount of time when Minutes The longer the beetroot is in the There will be a timer of 30
beetroot is soaking in water the longer it may lose or minutes at the drop of the first
vinegar gain pigment. This will affect beetroot cylinder in the test tube.
the results if some experiments The same process will need to
and trials are removed at happen for the other experiments.
different times.
The same beetroot N/A Using different beetroots This will be controlled by
creates space for outliers in the attempting to use the same
result. beetroot for each experiment.
1.6 Materials
- Graduated Cylinder (25ml)
- Ruler
- Pipette
- Knife
- Cutting board
- Tweezers
- 0.7cm cork borer
- 10 beet roots (25 beetroot cylinders)
- President’s Choice rice vinegar (6% acetic acid)
- No Name white vinegar (5% acetic acid)
- President’s Choice white wine vinegar (6% acetic acid)
- Krinos white balsamic vinegar (6% acetic acid)
- Bragg apple cider vinegar (5% acetic acid)
- 10 test tubes
- Colorimeter
- Lab quest
- 1 Electric balance
1.7 Methodology:
1. Using a cork borer that has a diameter of 0.7cm, cylinders of beetroots were made of the same
dimensions (4cm long) using a sharp blade and a cutting board. Five of these cylinders must be
made for each experiment and weighted.
2. Then using a graduated cylinder, 20ml (± 0. 5) of vinegar was poured into each test tube.
3. The beetroot cylinder was left to soak for 30 minutes. While waiting, connect the colorimeter to
the lab quest and set your colorimeter to the 430nm value. Let it start up for 5 minutes then use
an empty washed cuvette and fill it up with the vinegar being used.
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