11 mark
Which option correctly completes the sentence below?
Photosynthesis is an example of _________.
An exothermic reaction.
A catabolic reaction.
An endothermic reaction.
Net energy loss.
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Syllabus Edition
First teaching 2023
First exams 2025
|
Photosynthesis (SL IB Biology)
Exam Questions
2 hours33 questions21 mark
A plant is grown in increasing concentrations of carbon dioxide, whilst other factors are kept constant.
What will happen to the rate of photosynthesis?
There will be no change.
It will increase to a maximum level.
It will keep increasing exponentially.
It will increase to an optimal level and then decrease.
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31 mark
With reference to the experimental set-up shown, which option correctly describes how the rate of photosynthesis can be directly measured?
Measuring the distance between the light and plant.
Measuring the change in biomass of the plant.
Measuring the carbon dioxide production by counting bubbles.
Measuring the oxygen production by counting bubbles.
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11 mark
Which of the following statements about photosynthesis is incorrect?
Energy captured from sunlight is used to fix carbon.
Photosynthesis is an anabolic reaction.
Photosynthesis only occurs in chloroplasts.
Photosynthesis is an endothermic reaction.
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21 mark
Paper chromatography can be used to separate photosynthetic pigments obtained from chloroplasts. The chromatography strip shows distinct coloured pigment bands. Which pigments are represented by bands 3 and 4?
Carotenes and Xanthophylls.
Carotenes and Chlorophyll a.
Carotenes.
Chlorophyll a and Chlorophyll b.
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31 mark
Which is the most correct statement about chlorophyll?
Absorbs red and blue light.
Reflects red and blue light, and absorbs green light.
Absorbs the full spectrum of light equally.
Only absorbs blue light.
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41 mark
The graph shows how the rate of photosynthesis is affected by temperature. Which statements correctly explain why the rate decreases at higher temperatures?
- Photosynthesis is an enzyme-catalysed metabolic pathway.
- Enzymes denature at high temperatures.
- Less carbon dioxide is available in the atmosphere.
- Rate of respiration increases
I and II
II and III
I, II and III
All the above
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51 mark
A plant is grown in standard atmospheric air with a carbon dioxide concentration of approximately 400 ppm. The level of carbon dioxide is then reduced to below 100 ppm. Which of the following statements about the plant are correct?
- The rate of photosynthesis increases.
- Respiration and growth continue until stored sugars are used up.
- The rate of photosynthesis decreases.
- Metabolism is reduced to save energy.
I only
I only II
II and III
II, III and IV
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61 mark
The following graphs show the absorption spectrum for chlorophyll a and the action spectrum showing the relative rate of photosynthesis at different wavelengths of light.
Why do the graphs look different?
Other pigments are involved in photosynthesis which can absorb light of different wavelengths.
Only visible light is absorbed by photosynthetic pigments.
Photosynthesis can only occur in blue and red wavelengths of light.
Chlorophyll a inhibits the absorption of green and yellow light.
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71 mark
A student designed the following experimental set-up to measure the effect of light intensity on the rate of photosynthesis. The experiment was repeated three times.
| Distance from lamp (cm) | Number of bubbles per minute | ||
| Replicate 1 | Replicate 2 | Replicate 3 | |
| 10 | 99 | 81 | 64 |
| 20 | 63 | 43 | 45 |
| 30 | 31 | 18 | 13 |
| 40 | 18 | 7 | 8 |
| 50 | 15 | 6 | 4 |
The results were inconsistent, how could the experimental set-up be improved?
Measuring the change in biomass of the plant.
Using cooled, boiled water to remove dissolved oxygen.
Replacing the water with sodium hydrogen carbonate solution.
Using a red light source.
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81 mark
The effect of different colours of light on the growth of Arabidopsis thaliana (thale cress) seedlings was studied. Three different colours of light were tested and measurements of seedling height, shoot length, and biomass were taken.
| Colour of light | Wavelength of light (nm) | Height of seedlings (cm) | Shoot length (cm) | Total biomass (g) |
| Blue | 450 | 3.5 | 2.8 | 2.4 |
| Orange | 600 | 2.3 | 2.0 | 2.8 |
| Red | 630 | 7.4 | 6.1 | 3.7 |
What conclusions can be drawn from the data?
White light gives the optimal conditions for photosynthesis.
There is a linear relationship between wavelength of light and plant growth.
Red light enhances plant growth.
There is no correlation between total biomass and plant height.
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1
1 mark
1 markWhich of the following statements relating to photosynthesis are correct?
I. Temperature is a limiting factor of photosynthesis.
II. Chlorophyll absorbs wavelengths of light at either end of the visible light spectrum.
III. Plants have a positive net carbon dioxide uptake.
IV. The only photoautotrophic organisms include plants and algae.
I. II. III. and IV.
II. and III.
I. II. and III.
I. and II.
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21 mark
1 markThe graph shows the absorption spectra for chlorophyll a.
Which of the following statements, relating to the absorption spectra for chlorophyll and the action spectrum of photosynthesis for green plants, are correct?
I. The absorption spectra of chlorophyll pigments are obtained by measuring their absorption of indigo, violet, blue, green, yellow, orange and red light, whereas the action spectrum of chlorophyll is the wavelengths of light that bring about photosynthesis.
II. The absorption spectra for chlorophyll and the action spectrum of photosynthesis are both plotted using % absorbance on the Y-axis.
III. The absorption spectra for chlorophyll and the action spectrum of photosynthesis both display two main peaks, including a larger peak in the red region (~450 nm) and a smaller peak in the blue region (~670 nm).
IV. The absorption spectrum of chlorophyll displays a trough in the green/yellow portion of the visible spectra (~550 nm), whereas the action spectrum of photosynthesis does not.
I only
I and III
I, II, and III
II, III and IV
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31 mark
1 markA student investigated the effect of light intensity on the rate of photosynthesis by counting the number of bubbles released from the pondweed Elodea canadensis. The results are shown below.
Which of the following statements relating to the utilisation of carbon dioxide at differing light intensities are correct?
I. The rate of carbon dioxide uptake always increases proportionately as light intensity increases.
II. The rate of carbon dioxide uptake will decrease as the plant is moved away from the lamp.
III. The rate of carbon dioxide uptake will be greater at increased light intensities.
IV. The rate of carbon dioxide uptake becomes constant at increased light intensities as carbon dioxide becomes a limiting factor.
I. II. III. and IV.
I. and II.
II. and III.
II. III. and IV.
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41 mark
The graph below shows how varying light intensity affects the rate of carbon dioxide absorption by leaves, at different, fixed temperatures and carbon dioxide concentrations.
Which of the following rows correctly identifies the possible limiting factor for photosynthesis at I, II, III and IV?
| I | II | III | IV | |
| A. | CO2 concentration | Light intensity | Temperature | Photosynthetic capacity |
| B. | Light intensity | Temperature | CO2 concentration | Photosynthetic capacity |
| C. | Temperature | Light intensity | Photosynthetic capacity | CO2 concentration |
| D. | Light intensity | CO2 concentration | Temperature | Photosynthetic capacity |
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