Syllabus Edition

First teaching 2023

First exams 2025

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Photosynthesis (HL IB Biology)

Exam Questions

5 hours66 questions
11 mark

In plants, oxygen can be thought of as a waste product of photosynthesis.

Where does the oxygen come from?

  • The photolysis of water.

  • Molecular oxygen in the atmosphere.

  • The splitting of carbon dioxide.

  • The breakdown of glucose.

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21 mark

Which of the following statements best describes why the majority of plants appear green?

  • Chlorophyll reflects the light most strongly in the green portion of the visible spectrum.

  • Chlorophyll absorbs light most strongly in the green portion of the visible spectrum, followed by the red portion.

  • When chlorophyll absorbs light, it releases electrons.

  • The human eye is more sensitive to green light.

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31 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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41 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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51 mark

With reference to the experimental set-up shown, which option correctly describes how the rate of photosynthesis can be directly measured?

e-5

  • 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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6
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1 mark

Which of the following correctly identifies the location of the light-dependent reactions?

  • In the stroma of the chloroplast

  • In the thylakoid intermembrane space

  • On the outer membrane of the mitochondria

  • On the outer membrane of the chloroplast

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7
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1 mark

Which of the following would be a suitable definition for the term 'photolysis'?

  • The splitting of water molecules using light energy

  • The splitting of an oxygen molecule into oxygen atoms

  • The splitting of water into protons, neutrons and oxygen

  • The splitting of water by means of hydrolysis reactions

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8
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1 mark

Which of the following would not be considered an adaptation of chloroplasts to photosynthesis?

  • The granal stacks create a large surface area for the maximum absorption of light by the photosystems

  • The presence of ribosomes allows for the formation of the necessary polysaccharides involved with photosynthesis

  • The chloroplast DNA contains genes coding for proteins and enzymes used in photosynthesis

  • The stroma contains enzymes that catalyse the reactions of the light-independent stage

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9
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1 mark

During which of the following processes does carbon fixation occur?

  • Light dependent reactions

  • Photolysis

  • Calvin cycle

  • Chemiosmosis

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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?

2-8-biology-q1-ib-hl-mcq

  • 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?

biology-2-8-q4-ib-hl

  1. Photosynthesis is an enzyme-catalysed metabolic pathway.
  2. Enzymes denature at high temperatures.
  3. Less carbon dioxide is available in the atmosphere.
  4. 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? 

  1. The rate of photosynthesis increases.
  2. Respiration and growth continue until stored sugars are used up.
  3. The rate of photosynthesis decreases.
  4. 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.

biology-2-8-q6-ib-hl-

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.

biology-2-8-q7-ib-hl

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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91 mark

In photosynthesis, the following reaction occurs: 

2H2O → 4e- + 4H+ + O2 

What happens to the oxygen generated through this reaction?

  • It is converted into water.

  • It is incorporated into glucose molecules.

  • It is used in cellular respiration.

  • It diffuses out of the plant cell.

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101 mark

The image below shows a chloroplast.q1_8-3_photosynthesis_ib_biology_hl_mcq

Identify the location of the light independent and light dependent reactions.

 

Location of light independent reaction

Location of light dependent reaction

A

1

3

B

3

2

C

1

4

D

3

1

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    111 mark

    Which events occur during the light dependent stage of photosynthesis?

    1. ATP is produced
    2. NADP is reduced to NADPH
    3. Water splits into protons, electrons and oxygen
    4. NADPH is oxidised to NADP
    • All of them

    • I, II, III

    • I, III, IV

    • II, III, IV

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    121 mark

    What are the functions of excited electrons in photosynthesis?

    1. To generate a proton gradient
    2. To reform RuBP
    3. To reduce G3P
    4. To reduce NADP
    • I, III, IV

    • II, III, IV

    • I, IV

    • I, III

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    131 mark

    Which event occurs during non-cyclic photophosphorylation?

    • Dephosphorylation of ATP

    • Reduced NADH is synthesised

    • Chemiosmosis in the stroma of the chloroplast

    • Excited electrons enter an electron transport chain

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    141 mark

    Which process is not part of the light-independent reaction of photosynthesis?

    • Glycerate-3-phosphate is converted to triose phosphate

    • Rubisco is regenerated from triose phosphate

    • ATP is dephosphorylated to ADP

    • Carboxylation of RuBP

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    151 mark

    What allows the cyclic nature of the Calvin cycle?

    • Reduced NADP accumulates in the stroma

    • A buildup of ATP in the stroma 

    • Decarboxylation of Ribulose bisphosphate

    • The catalytic nature of RuBP 

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    161 mark

    Where is ATP synthase located in the chloroplast below?q1_8-3_photosynthesis_ib_biology_hl_mcq

    • 1

    • 2

    • 3

    • 4

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    171 mark

    The thylakoid intermembrane space has a small volume.

    What advantage does this have for photosynthesis?

    • High proton concentration can be rapidly developed

    • Short diffusion pathway for the movement of hydrogen ions

    • High electron concentration can be readily developed

    • Rapid accumulation of reduced NADP

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    1
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    1 mark

    Which 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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    2
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    1 mark

    During photosynthesis, the following reaction occurs.

                2H2O → 4e- + 4H+ + O2

    Which of the following statements relating to this reaction is not correct?

    • All of the oxygen derived from the splitting of water is used for cellular respiration

    • Water is broken down using energy derived from light

    • The splitting of water is an essential step in photosynthesis

    • Electrons derived from the splitting of water are used in subsequent stages of photosynthesis

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    3
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    1 mark

    The graph shows the absorption spectra for chlorophyll a.

    jJ~TDErV_h-3

    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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    4
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    1 mark

    A 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.

    gdmplJMu_7

    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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    51 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.jmdWK3gv_h-5


    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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      6
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      1 mark

      The diagram below shows the Calvin cycle of the light-independent reactions.

      13-1-fig-5-1

      Which of the following correctly identifies compound M to P?

        M N O P
      A. carbon dioxide ribulose bisphosphate glycerate 3-phosphate glucose
      B. carbon dioxide glycerate 3-phosphate ribulose bisphosphate glucose
      C. Rubisco glycerate 3-phosphate ribulose bisphosphate triose phosphate
      D. carbon dioxide triose phosphate glycerate 3-phosphate ribulose bisphosphate

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        7
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        1 mark

        The following steps describe non-cyclic photophosphorylation involving the electron transport chain.

        1. Electrons from the photolysis of water replace lost electrons from photosystem II
        2. Light passes to primary pigments in photosystem I and II
        3. Electrons are passed from photosystem II to photosystem I via electron transport chain
        4. Energy is released to synthesise ATP
        5. Electrons are excited to a higher energy level

        Which of the following represents the correct sequence of the steps?

        • II. → V. → IV. → III. → I.

        • V. → IV. → III. → II. → I.

        • II. → V. → III. → IV. → I.

        • V. → III. → IV. → II. → I.

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        8
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        1 mark

        The following molecules are all involved with the process of photosynthesis.

        1. Glucose
        2. ATP
        3. Water
        4. Reduced NADP
        5. Carbon dioxide

        Which of these molecules are involved with both the light dependent and light independent reactions?

        • I. and III.

        • II. and IV.

        • I., II. and IV.

        • II., IV. and V.

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        9
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        1 mark

        Which of the following provides the best explanation of the process illustrated in the diagram?8-3_q4h

        • Photosystem I and ferredoxin is involved with the reduction of NADP so that the hydrogen can be used during the light independent stage of photosynthesis

        • Photosystem II and ferredoxin is involved with the reduction of NADP so that the hydrogen can be used during the light independent stage of photosynthesis

        • Photosystem I and plastoquinone is involved with the reduction of NADP so that the hydrogen can be used during the light independent stage of photosynthesis

        • Photosystem I and ferredoxin is involved with the reduction of NADP so that the hydrogen can be used during the light dependent stage of photosynthesis

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        10
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        1 mark

        Which of the following statements is not correct with regards to chemiosmosis in photosynthesis?

        1. Protons move down their concentration gradient through ATP synthase located in the chloroplast membrane
        2. The photolysis of water provides protons needed for chemiosmosis to occur
        3. ADP is phosphorylated to ATP due to the energy released by the movement of electrons down the electron transport chain
        4. A high concentration of protons build up outside the intermembrane space, creating a concentration gradient
        • I. and IV. only

        • II. and III. only

        • I., III. and IV.

        • II., III. and IV.

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