Mohammed Salam Unit 6: LA C
Safely undertake the project, collecting, analysing and presenting the results
Abstract:
The aim of the investigation is to determine the effects of oxygen bubble production in
pondweed by altering the light intensity. The hypothesis was that the different light intensity
will have a significant effect on the rate of oxygen production in pondweed. The length of
oxygen bubble produced in 3 minutes was taken at altering light intensities and temperatures.
The results that have been produced from the practical has shown that different light
intensities do have a significant effect on the rate of oxygen production in pondweed. The
hypothesis that was stated in the practical has been proved and the null hypothesis was
rejected. A bar graph was also produced after the practical to determine the trends between
the light source and the pondweed when producing oxygen bubbles at different distances. As
when the light intensity decreased by increasing the distance between the pondweed and the
light the rate of oxygen production also decreased. A temperature was also another factor
which was also used in the practical 15 degrees and 25 degrees it has shown in the result table
and bar graph that when increasing the temperature, it also increased the oxygen bubble
length.
Hypothesis:
If the light intensity increases on the pondweed (elodea) it will have a significant effect on the
rate of oxygen production in pondweed. This is shown in a study by K. Gadd (2012) where the
rate of photosynthesis increases linearly when increasing the light intensity, the light photons
from the sunlight are ionised by the leaf chlorophyll which then increases the production of
ATP. The photosynthesis balanced equation is 6CO2 + 6H2O = C6H12O6 + 6O2 the oxygen and
glucose are the by – products from the photosynthesis. Another study is shown by Manisha
Minni (2021) where with ATP energy, NADPH combines with CO2 and converts it into glucose.
The dark reaction as known as carbon assimilation occurs while the photosynthesis process
takes place and absorbs carbon dioxide and then they are converted into glucose, the equation
for photosynthesis is 6CO2 + 6H2O = C6H12O6 + 6O2 . There is another evidence from the
literature review which reinforces with Manisha Minni studies it is shown by Evans, J.R. (2013)
where the photosynthesis occurs in plants which captures sunlight and converts it into
biochemical energy which is glucose. The process starts when the plants absorb the sunlight it is
done by the plant organelles, chlorophyll. Once the sunlight is absorbed by chlorophyll oxygen
is produced. Carbon assimilation is introduced when the CO2 are absorbed in plants via process
of photosynthesis which produces glucose. Finally, another evidence from the literature review
which also reinforces with Evans, J.R. (2013) source which is shown in the evidence by Sushmita
Rout (2021) where in plants, they have green pigment which absorbs sunlight the green
pigment in plants is chlorophyll this is important because it captures red light and blue light.
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,Mohammed Salam Unit 6: LA C
The regions in chloroplasts are grana and stroma are where the photosynthesis takes place.
Grana has disc – like structures and they are stacked up on one of another. The light –
dependent stage is the initial process where the thylakoids in the chloroplasts they use sunlight
to breakdown the water molecule into H+ and OH-. During the photolysis of water molecules,
oxygen is formed by bonding to other oxygen atoms. As ATP is produced by the additional of
third phosphate to ADP, the hydrogen ions contribute energy to ATP synthase which are the
enzymes in plant cells. NADP+ and H+ ions are bonded together which makes energy – carrying
molecule NADPH in this reaction.
Preliminary method:
1. The pondweed should be well illuminated before doing the experiment.
2. Set up the apparatus in the darkened room by placing the elodea pondweed (10cm) in the
inverted glass funnel within a beaker that contains water, eliminate as much of light as possible
in the room like closing the curtains/blind folds.
3. Place the LED on the specific place where the practical will be performed like on the table,
when placing the lamp ensure to place it where it faces the pondweed.
4. The capillary tube should be connected to the glass funnel via rubber tubing and the syringe
should be connected to the capillary tube so that the measurements can be made by drawing
up the bubbles through the apparatus.
5. Calibrate the weighing balance, 6.25 grams should then be added this is done by placing the
sodium hydrogen carbonate (NaHCO3) on the top pan of the weighing balance and make sure
only to correct it to 2 decimal places.
6. The sodium hydrogen carbonate should be added in the 250cm3 beaker and slowly pour the
water until it has reached up to 250cm3.
7. Place the water level just above the funnel which creates a seal in the apparatus to prevent
oxygen loss in the apparatus when doing the experiment.
8. Place the apparatus in the water bath at a controlled temperature of 15 degrees with 5% of
sodium hydrogen carbonate concentration, place the thermometer in the water bath and
ensure that it is 15 degrees throughout the experiment.
9. Heat screen should be added in between the pondweed and the LED before turning it on, this
prevents the heat coming from the lamp source when it is on which could alter the
effectiveness of the results.
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, Mohammed Salam Unit 6: LA C
10. Operate the LED as soon it is turned turn on, operate the stopwatch, and set the timer to 5
minutes to ensure the pondweed is used to the new environment. After the 5 minutes of
configuring the environment for the pondweed, begin the experiment by starting the timer to 5
minutes.
11. When the 5 minutes is done, stop the stopwatch and turn off the LED and draw up the
oxygen bubbles by pulling the syringe slowly so that it enters the capillary scale. The bubbles
are measured by placing the scale of capillary tube on against the graph paper the bubbles
should be measured in mm.
12. Record the length of bubbles in a result table.
13. Remove the bubbles from the capillary tube and place the capillary tube back into the
apparatus.
14. Move the LED 8cm further back use the metre ruler for better accuracy, operate the LED,
start the stopwatch for the pondweed to acclimatise again for 5 minutes.
15. Turn off the LED, when the 5 minutes of time has reached and then draw up the oxygen
bubbles produced in the pondweed by pulling the syringe slowly so that it enters the capillary
scale. Measure the bubbles by placing the scale of capillary tube on against the graph paper,
the bubbles should be measured in units (mm).
16. Record the length of bubble in the result table.
17. Repeat this procedure by moving the lamp away using the metre ruler like 0, 8, 14, 16, and
20cm.
18. After done the experiment with the temperature of 15 degrees repeat this entire method
including the repeats to investigate further by setting the water temperature to 25 degrees.
19. Finally, convert the raw data into a table, and there should be two distinct results for
analysis and statistical testing.
Main method:
1. The pondweed should be well illuminated before doing the experiment.
2. Set up the apparatus by placing the elodea pondweed (10cm) in the inverted glass funnel
within a beaker that contains water.
3. Place the lamp on the specific place where the practical will be performed like on the table,
when placing the lamp ensure to place it where it faces the pondweed.
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