Syllabus Edition

First teaching 2023

First exams 2025

|

Photosynthesis as an Energy Transfer Process (CIE A Level Biology)

Exam Questions

2 hours13 questions
1a
Sme Calculator
3 marks

Fig. 1 below shows a diagram of a chloroplast.

kOCzB7oQ_1-1

Fig. 1

Identify the parts of a chloroplast labelled A - C in Fig. 1.

1b
Sme Calculator
1 mark

The part of the chloroplast labelled B in Fig. 1 contains various photosynthetic pigments.

Suggest why chloroplasts contain more than one different photosynthetic pigment.

1c
Sme Calculator
2 marks

The pigments in a chloroplast can be separated and identified using a technique called thin-layer chromatography.

After extracting pigments from a spinach leaf, a student carried out thin-layer chromatography.

Some of their results can be seen in Fig. 2 below.

Z6gEpBOj_2-2

Fig. 2

Use the equation provided to calculate the Rf values for pigments X and Y in Fig. 2.

Rf space equals fraction numerator space Distance space moved space by space pigment over denominator Distance space moved space by space the space solvent end fraction

1d
Sme Calculator
2 marks

Table 1 contains value ranges for the Rf values of some common photosynthetic pigments.

Table 1

pigment Rf value range
carotene 0.89 - 0.95
neoxanthin 0.05 - 0.11
chlorophyll a 0.64 - 0.69
chlorophyll b 0.53 - 0.62
pheophytin a 0.78 - 0.86

Use your answers to part (c) to identify pigments X and Y from Fig. 2.

Did this page help you?

2a
Sme Calculator
1 mark

Most plants appear green to the human eye.

With reference to chlorophyll, explain why plants are green.

2b
Sme Calculator
2 marks

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. The results of the study are shown in Table 1 below.

Table 1

Colour of light Wavelength of light / nm Height of seedlings / cm Shoot length / cm Total biomass / g
Blue 450 2.3 2.0 2.4
Orange 600 3.5 2.8 2.8
Red 630 7.4 6.1 3.7

State what can be concluded about the effect of different colours of light on the growth of Arabidopsis thaliana from the data shown.

2c
Sme Calculator
1 mark

Oxygen is waste product of photosynthesis.

Identify the process by which this oxygen is produced.

2d
Sme Calculator
2 marks

State the two products of the light-dependent stage of photosynthesis.

Did this page help you?

3a
Sme Calculator
1 mark

Fig. 1 below shows the reactions of the Calvin cycle.

VVhRr~tr_4

Fig. 1

Identify Enzyme X in Fig. 1

3b
Sme Calculator
2 marks

Identify the molecules required at the positions marked Y and Z to convert GP into TP.

3c
Sme Calculator
2 marks

One of the products produced from TP is hexose sugars.

Give two uses for hexose sugars inside plant cells.

3d
Sme Calculator
2 marks

Identify one other product that is made during the Calvin cycle and state its role inside plant cells.

Did this page help you?

42 marks

Fig. 1 shows an electron microscope image of a chloroplast.

MGfr8HpH_1

Fig. 1

(i)

Identify structure B in Fig. 1.

[1]

(ii)

State the role of structure in photosynthesis.

[1]

Did this page help you?

5a
Sme Calculator
2 marks

Photosynthesis is spilt into two sets of reactions. The first set of reactions involves a process known as photoactivation.

Describe the events of photoactivation.

5b
Sme Calculator
2 marks

Photoactivation can occur during either cyclic or non-cyclic photophosphorylation.

State two differences between cyclic and non-cyclic photophosphorylation.

5c
Sme Calculator
1 mark

The second set of reactions during photosynthesis rely on the activity of the enzyme rubisco. 

State the precise location of the enzyme rubisco. 

5d
Sme Calculator
1 mark

Describe the role of the enzyme rubisco in photosynthesis.

Did this page help you?

1a3 marks

Chloroplasts contain photosynthetic pigments.

Describe the arrangement of the pigments inside a chloroplast.

1b4 marks

Outline the following processes connected to the pigment arrangements described in part a):

(i)

Photoactivation

[2]

(ii)

Photolysis

[2]

1c3 marks

In addition to the processes outlined in part b) the light dependent reactions of photosynthesis also involve the processes of oxidation and reduction.

Explain where oxidation and reduction occur during the light dependent reactions.

1d
Sme Calculator
4 marks

Pigment molecules are arranged in light-harvesting clusters known as photosystems: photosystem I (PSI) and photosystem II (PSII). These are involved in different photophosphorylation reactions of the light-dependent stage of photosynthesis. 

i)
Identify the two types of photophosphorylation reactions that occur during the light-dependent stage of photosynthesis.

[1]

ii)
Compare the two types of photophosphorylation.
[4]

Did this page help you?

2a3 marks

Fig. 1 shows some of the events of the light independent reactions.

13-1-fig-4-1Fig. 1

(i)

Identify the process shown in Fig.1.

[1]

(ii)

Give two reasons for your answer to part (i).

[2]

2b4 marks

The element cadmium, sometimes present in polluted soils, is toxic to plants even at low concentrations. Research has shown that cadmium can bind to photosystem II, impacting the process marked A in Fig 1.

(i)

Name the process marked in Fig.1.

[1]

(ii)

With reference to your answer to part i), outline the impact that cadmium would have on photosynthesis.

[3]
2c5 marks

Describe the process taking place at the position marked B in Fig.1.

Did this page help you?

3a3 marks

Fig.1 shows a representation of the light independent stages of photosynthesis.

13-1-fig-5-1Fig. 1

From Fig.1, identify:

(i)

Compound M.

[1]

(ii)

Compound O.

[1]

(iii)

The enzyme that catalyses the reaction between compounds M and O.

[1]

3b3 marks

With reference to Fig.1 explain how the products of the light dependent reactions are used in the light independent reactions.

3c4 marks

Compound P is a product of the light independent reactions.

(i)

Give three other molecules that could be formed from compound P inside plant cells.

[3]

(ii)

Name the type of reaction that would convert compound P into a polymer.

[1]
3d2 marks

Explain one reason why compound P is converted into other molecules such as those given in part c) i) rather than being stored as a six-carbon (6C) molecule in the cells.

[2]

Did this page help you?

4a
Sme Calculator
3 marks

Fig. 1 is a transmission electron micrograph of a chloroplast.

fig7-1-qp-octnov-2018-9700-41

Fig. 1

Many compounds and structures involved in photosynthesis are located in a chloroplast.

Using the labels A, B or C, complete Table 1 to show the location of four of these compounds or structures.

You may use each of the letters A, B and C once, more than once, or not at all.

Table 1

compound or structure location
ATP synthase  
rubisco  
starch grain  
phospholipid bilayer  

[3]

4b
Sme Calculator
3 marks

Elodea canadensis is an aquatic plant that lives submerged in freshwater.

Equal‐sized plants of E. canadensis were exposed to different wavelengths of light for the same period of time. As each plant photosynthesised, the number of bubbles of oxygen leaving the plant was counted.

For each wavelength, the rate of oxygen production was calculated.

The results are shown in Fig. 2.

fig7-2-qp-octnov-2018-9700-41

Fig. 2

Describe and explain the results shown in Fig. 2

4c
Sme Calculator
2 marks

Chlorophyll b, carotene and xanthophyll are known as accessory pigments.

Describe the role of the accessory pigments in photosynthesis.

Did this page help you?

5a
Sme Calculator
3 marks

Fig.1 is an outline diagram of the Calvin cycle.

fig7-1-qp-octnov-2018-9700-42

Fig. 1

With reference to Fig. 1, describe stage A of the Calvin cycle.

5b
Sme Calculator
2 marks

Outline the importance of the light-dependent reactions in allowing stage B of the Calvin cycle, as indicated in Fig. 1, to proceed.

5c
Sme Calculator
3 marks

Substance C in Fig. 1 represents a variety of complex organic molecules. 

Give three named examples of substance C and the Calvin cycle intermediates from which these examples are produced.

Did this page help you?

1a
Sme Calculator
3 marks

Corals grow in shallow seawater. Corals consist of colonies of small animals called polyps. These polyps have photosynthetic protoctists called algae within their cells, which is advantageous both to the coral polyps and to the algae.

The algae that live within the cells of coral polyps can also live independently as free-living algae.

The rate of photosynthesis of algae that live within the cells of coral polyps is higher than that of free-living algae.
 
Suggest and explain why the rate of photosynthesis in algae that live within the cells of coral polyps is higher than that of free-living algae.
1b
Sme Calculator
3 marks

The algae that live within the cells of coral polyps have five different chloroplast pigments.

Table 1 shows the light wavelengths at which each algal chloroplast pigment shows its two largest peaks of light absorption.

Table 1

chloroplast
pigment
peak 1
wavelength / nm
peak 2
wavelength / nm
chlorophyll a 430 662
peridinin 456 485
chlorophyll c2 450 396
dinoxanthin 442 471
β-carotene 454 480

 

Corals can be kept in glass tanks that are usually lit by lamps radiating mainly violet and blue light, with wavelengths in the range of 400 nm to 490 nm.

With reference to Table 1, suggest why lamps radiating mainly violet and blue light are expected to increase the growth of coral polyps more than lamps radiating light of all wavelengths.

1c
Sme Calculator
4 marks

Photosynthesis in the algae living within the cells of coral polyps is the same as photosynthesis in plant cells.

Outline the process of cyclic photophosphorylation.

Did this page help you?

2a
Sme Calculator
2 marks

Paper chromatography can be used to separate photosynthetic pigments obtained from chloroplasts.

Fig. 1 shows the chromatography strip with distinct pigment bands.

h-1a

Fig. 1

The four bands represent four pigments: chlorophyll a, chlorophyll b, xanthophylls and carotenes (but not necessarily in that order). A student suggests bands 3 and 4 most likely represent the two chlorophyll pigments.

Explain why the student is correct. 

2b
Sme Calculator
3 marks

Describe how to accurately identify the pigments in the chromatogram shown in part (a).

2c
Sme Calculator
1 mark
The photosynthetic pigments from two aquatic algae, green alga genus Oedogonium and red alga genus Palmaria, were separated by thin layer chromatography.




Fig. 2 shows the chromatograms.

h-1c

Fig. 2

Palmaria also contain a red pigment known as phycoerythrin. The pigment appears red because it absorbs blue light and reflects red light. The pigment phycoerythrin is absent from the chromatogram above.

Suggest why this might be.

2d
Sme Calculator
2 marks

Light of shorter wavelengths penetrates water to greater depths than light of longer wavelengths.

Using information here and from part (c), suggest why red algae such as Palmaria can live at greater depths than many other aquatic algae.

Did this page help you?

3a
Sme Calculator
5 marks

The concentration of carbon dioxide gas in the air of a woodland changes over 24 hours. Carbon dioxide concentrations can also vary depending on the height above the ground at which a gas measurement is taken.

Explain the variation in carbon dioxide concentration in woodland over time and at different heights. Assume that there is no air movement caused by wind throughout the 24 hours.

3b
Sme Calculator
2 marks

A team of researchers investigated the effect of changing the carbon dioxide concentration on the levels of glycerate-3-phosphate (GP) and ribulose bisphosphate (RuBP) in photosynthesising cells.

Table 1 shows the results obtained when the carbon dioxide concentration was reduced.

Table 1

Photosynthetic
intermediate
Level before
experiment /
arbitrary units
Level after experiment / arbitrary units
1.0% CO2 0.003% CO2
RuBP 18 18 37
GP 36 36 17

Explain the results for RuBP and GP at 0.003% carbon dioxide concentration.

3c
Sme Calculator
2 marks

The researchers carried out a similar experiment but increased the carbon dioxide concentration from 1.0 % to 2.0 %. The relative levels of GP and RuBP remained the same both before and after the experiment.

Explain two reasons why this might be the case.

Did this page help you?

4a3 marks

Fig. 1 shows the absorption spectra for three different photosynthetic pigments.

k-CLt6ei_5

Fig. 1

Compare the absorption spectra of chlorophyll b and carotenoids shown in Fig.1.

4b2 marks

With reference to Fig. 1:

(i)

Suggest the colour of carotenoid pigments.

[1]

(ii)

Explain your answer to part (i).

[1]

4c2 marks

It is also possible to represent action spectra on a graph like that shown in Fig. 1.

(i)

State how the information represented by an action spectrum is different to that represented by an absorption spectrum.

[1]
(ii)

Sketch a suggested action spectrum onto the graph shown in Fig.1.

[1]
4d4 marks

A researcher wanted to investigate the wavelengths of light that hit the ground in a woodland area. They measured the wavelengths of direct sunlight and sunlight that had passed through the tree canopy. Fig. 2 shows their results.

Q_yK_SYH_6

Fig. 2

Only a small number of plant species are found on the ground below the trees in woodland areas.

Use Fig. 1 and 2 to suggest why.

Did this page help you?

5a
Sme Calculator
3 marks

Some species of deep ocean-living bacteria carry out the process of chemosynthesis. Chemosynthesis uses energy stored in chemicals such as methane, hydrogen sulfide (H2S) and carbon dioxide, to produce glucose.

A simplified example of a chemosynthesis reaction is shown below:

6CO2  + 12H2S → C6H12O6 + 6H2O + 12S

Use your knowledge of photosynthesis to suggest the role of hydrogen sulfide in chemosynthesis.

5b
Sme Calculator
2 marks

A suspension of photosynthetic pigments was isolated from another species of aquatic bacteria. A reagent that is blue when oxidised and colourless when reduced was added to the suspension.

The suspension of pigments in blue reagent was exposed to sunlight and the blue colour disappeared.

Explain this observation.

5c
Sme Calculator
2 marks

In the same suspension, the concentration of glycerate-3-phosphate (GP) was also measured. It was found to increase during the addition of the blue reagent. 

Explain this observation.

5d
Sme Calculator
2 marks

The bacteria species described in parts (b) and (c) live underwater at a depth of 5 metres. Most of the light that penetrates to this depth falls at wavelengths of between 400-600 nm.

Suggest which photosynthetic pigment(s) is/are likely to be most abundant in these bacterial cells. Explain your answer.

Did this page help you?