Syllabus Edition

First teaching 2014

Last exams 2024

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Photosynthesis (DP IB Biology: HL)

Exam Questions

3 hours35 questions
1a
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2 marks

The diagram below shows a chloroplast. 

2-KY5nL8_image

Identify Structure A and state the reaction that takes place there.

1b
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2 marks

State two products of the light independent stage of photosynthesis. 

1c
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1 mark

ATP is required to drive the light independent reactions of photosynthesis.

Name the process which produces this ATP to be used in the light independent reactions?

1d
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2 marks

The light independent reactions are affected by temperature changes. Lowering the temperature slows down the light independent reactions. 

Explain why a low temperature slows down the light independent reactions. 

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2a
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1 mark

The diagram shows an electron micrograph of a chloroplast.

Annotate the diagram with the letter X to show the location of the light dependent stages of photosynthesis. 

chloroplast

2b
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2 marks

The photolysis of water is an important part of the process of light dependent stages of photosynthesis.

Describe what happens in the photolysis of water. 

2c
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1 mark

Chloroplasts contain more than one photosynthetic pigment. 

Suggest why chloroplasts contain more than one photosynthetic pigment.

2d
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2 marks

Describe a structure of the chloroplast that enables maximum absorption of light. 

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3a
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1 mark

The diagram below shows the Calvin cycle.

State the name of enzyme X shown in the diagram.

8Xz6ij-Q_image

3b
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2 marks

The molecules labelled Y and Z on the diagram are used to convert GP to TP.

Identify the molecules labelled Y and Z.

3c
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2 marks

One sixth of the TP is converted into usable products for the plant. One of these is hexose sugars.

State two uses of hexose sugars by plant cells.

3d
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2 marks

One sixth of TP is converted into usable products for the plant.  The remaining five sixths remain in the Calvin cycle.

Explain why it is important that not all the TP is converted to usable products. 

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4a
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1 mark

The diagram below shows some of the reactions taking place in the light dependent stages of photosynthesis.

State the exact location of the reactions shown.

yZzlophX_image

4b
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2 marks

Describe the process that occurs at location A in the diagram.

4c
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1 mark

The diagram from part a) shows the electron transport chain in the light dependent reaction.

At stage B, the electrons are involved in a series of reactions fundamental in the process of chemiosmosis.

State the type of reactions that take place at stage B.

4d
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3 marks

The diagram from part a) shows the movement of electrons through the electron transport chain.  

(i)
Identify the product labelled C.
[1]
(ii)
Describe the role of the electrons in the formation of product C.

[2]

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5a
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6 marks

One mark is available for clarity of communication throughout this question.

During the light independent stage of photosynthesis, carbon dioxide is converted into organic substances.

Describe how.  

5b
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6 marks

Outline the experiments preformed by Melvin Calvin to elucidate the pathways of carbon fixation. 

5c
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3 marks

ATP and NADPH are two products of the light-dependent reactions.

Describe the functions of each of these substances in the light-independent reactions.

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1a3 marks

 An experiment using radioactive carbon was carried out by scientists to investigate the Calvin Cycle. The algae Chlorella was exposed to radioactive carbon for different amounts of time. The algae was then analysed for radioactive compounds. The graph below shows the results.q1_photosynthesis_medium_ib_hl_biology_sq

Explain the changes in the amount of radioactive substances in the dark.

1b2 marks

Radioactive GP (glycerate 3-phosphate) was detected more rapidly than radioactive RuBP (ribulose bisphosphate). 

Use your knowledge of the Calvin cycle to explain this finding.

1c3 marks

Melvin Calvin carried out similar experiments in the 1950s. At the time his approaches were novel and only possible because of advances in apparatus and techniques.

Describe the techniques, and their purpose, used by Calvin that allowed him to identify the compounds involved in the Calvin cycle.

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2a3 marks

When plants are exposed to extremely high or low temperatures for a continued period of time, they are put under a lot of stress. This stress greatly impacts the rate of photosynthesis, in particular the light-dependent reaction of photosynthesis.

Explain why extreme cold leads to a decrease in the light-independent reaction.

2b1 mark

State the precise location of light-independent reactions in photosynthetic plants.

2c2 marks

Extreme cold can also cause a decrease in rubisco activity.

Explain why a decrease in the activity of  the enzyme rubisco limits the rate of photosynthesis.

2d2 marks

Describe the exact role of ribulose bisphosphate (RuBP) in the Calvin cycle.

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3a3 marks

The diagram below shows a diagram of a chloroplast.

q3a_photosynthesis_medium_ib_hl_biology_sq 

Identify the structures of a chloroplast labelled A-C in the diagram.

3b2 marks

Describe the adaptations of structures A and B from the diagram in part a).

3c2 marks

Plants can contain more than one type of chlorophyll, a and b.  Scientists grew plants that contained a mutant version of chlorophyll a. They investigated the effect of this mutation on the rate of photosynthesis.

 The scientists

  • Grew the mutant and normal plants in a range of light intensities
  • Isolated the chloroplasts from both types of plants
  • Measured the oxygen produced by the chloroplasts over a period of 20 minutes

Their results are shown in the graph below:

diagram-1

Explain why the scientists used the oxygen produced as a measure of the rate of photosynthesis.

3d2 marks

Use the graph to calculate the difference in oxygen produced by the chloroplasts from normal plants compared to the mutant plants at a light intensity of 400 Watts/m². 

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4a3 marks

The diagram below shows a representation of some of the reactions taking place during the light dependent reactions of photosynthesis. q4a_photosynthesis_medium_ib_hl_biology_sq-png

Explain the process that occurs at label A.

4b3 marks

Describe how the protein ferredoxin is involved in the reduction of NADP during the light dependent reaction.

4c2 marks

The diagram from part a) shows the loss of electrons from photosystem 2, but does not show how these electrons are replaced.

State and explain the source of the electrons that replace those lost at stage A.

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5a5 marks

One mark is available for clarity of communication throughout this question.

Crops absorb and use light energy for the production of photosynthetic products.

Describe how light energy is used by crop plants during the light-dependent reaction.

 

5b7 marks

The diagram below depicts the light-independent reactions of photosynthesis.

q5b_photosynthesis_medium_ib_hl_biology_sq 

Describe the mechanism of these reactions and explain how they allow for the continuous synthesis of 6-carbon sugars.

5c3 marks

Explain the role of protons in the light dependent reaction of photosynthesis.

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1a
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2 marks

Explain why the light independent reactions of photosynthesis stop in the absence of light. 

1b
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3 marks

Some species of bacteria that live on the ocean floor do not have access to light for photosynthesis. Instead, they use the process of chemosynthesis to make glucose using energy stored in substances such as methane, hydrogen sulfide (H2S) and carbon dioxide.  A simplified equation of one such reaction is shown below.

   carbon dioxide + water + hydrogen sulfide rightwards arrowglucose + sulfur + sulfur compounds

Use your knowledge of photosynthesis to suggest what hydrogen sulfide is used for in the process of chemosynthesis. 

1c
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1 mark

The rate of photosynthesis can be expressed as either gross or net rates. Gross photosynthesis is the total rate of carbon fixation (reduction of CO2) without considering that some of the CO2 is lost in respiration. Net photosynthesis is the carbon fixation rate minus the rate of CO2 loss in respiration.

The graph below shows the effect of temperature on the net rate of photosynthesis at three different light intensities and the effect of temperature on the rate of respiration. 

i0WQ5BBh_1

Use the graph to calculate the gross rate of photosynthesis at 15oC and low light intensity. 

1d
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3 marks

The average global temperature is 14oC. Scientists predict that over the course of the next 100 years, the average temperature could increase by up to 4oC. It is also predicted to become cloudier in many regions.

Use the graph to describe and explain how these changes are likely to affect the growth of plants. 

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2a
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4 marks

Researchers investigated the activity of two enzymes isolated from the leaf cells of lavender plants.

The two enzymes were:

  • Rubisco
  • Rubisco activase

The results of the investigation are shown in the graphs below.

xvqfxixa-image

The scientists concluded that heat stress reduces the activity of rubisco in plant leaves by affecting rubisco activate.

Use the data to evaluate their conclusion. 

2b
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1 mark

The enzyme rubisco catalyses the reaction between RuBP and carbon dioxide to form two molecules of glycerate-3-phosphate (GP). Rubisco can also catalyse a reaction between RuBP and oxygen to form one molecule of GP and one molecule of phosphoglycolate.

The reactions are shown in the diagram below.

Rubisco reactions SQ

Use the diagram to deduce to number of carbon atoms in one molecule of phosphoglycolate.

2c
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2 marks

The scientists investigated the effect oxygen concentration had on the absorption of carbon dioxide in leaves from tomato plants. The graph below shows their results.

Ke1bFgp8_2

Explain the results in the graph above using the diagram and information from part b) of the question. 

2d
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3 marks

Use all the information provided and your knowledge of the light-independent reaction to explain why the yield from tomato plants decreases at higher concentrations of oxygen. Note: Phosphoglycolate is not used in the light-independent reaction.

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3a
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1 mark

Some scientists were investigating photosynthesis in seaweed. During their investigation, they applied lights of different wavelengths to study the amount of light absorbed by the seaweed species.

Their results can be seen in the graph below.

photosynthesis-in-seaweed-wavelengths-and-absorption-sqState, with a reason, the types of pigments found in these species of seaweed.

3b
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2 marks

The scientists also measured the rate of the light-dependent reactions in the seaweed at each of the different wavelengths.

Species Mean rate of photosynthesis / arbitrary units

Lamp X
400 - 700 nm

Lamp Y
430 nm

A 1 250.3 (± 115.6) 920.2 (± 95.1)
B 290.4 (± 55.6) 276.6 (± 69.6)

Suggest how the scientists measured the rate of the light-dependent reactions.

3c
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6 marks

The scientists repeated the investigation twice more under the following conditions

  1. They increased light intensity from lamps X and Y
  2.  They increased the temperature of the investigation from 15 °C to 20 °C.

Discuss how these changes may affect the amount of oxygen produced by the seaweed

3d
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2 marks

The scientists concluded that both species of seaweed showed increased rates of photosynthesis under lamp X compared to lamp Y.

Evaluate this conclusion.

3e3 marks

The scientists also isolated a species of bacteria found to absorb light at the bottom of the ocean habitat where the seaweed were found. They found these bacteria absorbed light as shown by the absorption spectrum below:

absorption-spectrum-for-red-bacteria
absorption-spectrum-for-red-bacteria

Suggest the selective advantage to the bacteria of absorbing light as shown in this absorption spectrum.

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4a
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5 marks

'Weed wonder' is a weed killer designed to inhibit plastoquinone protein in chloroplasts of weeds.

Explain how this would affect the growth of weeds. 

4b
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6 marks

Compare and contrast the processes that occur in the electron transport chain (ETC) of the light dependent reaction with the electron transport chain in respiration.

4c
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2 marks

Oxidation and reduction are key to the metabolic pathways seen in photosynthesis.

Complete the table to indicate which substances are oxidised and which are reduced during the stages of photosynthesis.

Stage Substance Oxidised / reduced
Light-dependent NADP  
PSII after photoexcitation  
Light-independent GP  
NADPH  

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5a
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5 marks

One mark is available for clarity of communication throughout this question.

The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours.

Use your knowledge of photosynthesis to describe and explain these changes.  You can assume there is no air movement through wind throughout the 24 hour period.

5b
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5 marks

Certain types of ultraviolet radiation may induce the production of ATP in isolated plant cells by interacting with electrons found in photosystems.  

Use your knowledge of phosphorylation to explain how.

5c
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5 marks

Water absorbed by plants at the roots is carried to the leaves to be used in photosynthesis.

Explain the role of water in photosynthesis.

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