Photosynthesis (AQA GCSE Biology: Combined Science)

Exam Questions

2 hours15 questions
1a4 marks

Figure 1 shows some of the products and reactants involved in photosynthesis.

Figure 1

photosynthesis-products-and-reactants-4

Draw lines to show the following:

  • Which substances are the reactants of photosynthesis and which chemical formulae are used to represent these reactants.
  • Which substances are the products of photosynthesis and which chemical formulae are used to represent these products.

1b2 marks

Where would a land-based plant obtain the reactants of photosynthesis named in part (a)?

1c1 mark

Photosynthesis is described as an endothermic reaction because it uses energy transferred from the environment to the chloroplasts in the leaves of the plant.

Name where the energy comes from to drive photosynthesis.

1d1 mark

Figure 2 shows a plant cell with three cellular components labelled.

Figure 2

plant-cell

Identify which of the following options gives the correct name and function of P, Q and R.

  P Q R
A Chloroplast - stores water Cytoplasm - where chemical reactions take place Vacuole - stores water
B Vacuole -  the site of photosynthesis Chloroplast - stores water Cytoplasm - where chemical reactions take place
C Vacuole - stores water Cytoplasm - where the chemical reactions take place Chloroplast - the site of photosynthesis
D Chloroplast - the site of photosynthesis Cytoplasm - where chemical reactions take place Vacuole - stores water

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    2a2 marks

    Identify two limiting factors of photosynthesis.

    2b1 mark

    A student wanted to test the effect of light intensity on the number of bubbles produced by an aquatic plant over one hour.

    Figure 3 shows how the student set up his investigation.

    Figure 3

    factors-that-affect-photosynthesis-1

    Identify the gas being collected in the measuring cylinder which shows that the aquatic plant is photosynthesising.

    2c1 mark

    The student sets up the same experiment as shown in part (b) but this time, puts some ice cubes into the beaker also.

    Describe what effect this may have on the rate of photosynthesis of the plant.

    2d1 mark

    Water is usually not considered a limiting factor of photosynthesis.

    Which statement explains why?

    • Global warming means there are lots of floods and so there is plenty of water.

    • If water availability is low, plants close their stomata to stop transpiration, meaning that photosynthesis is limited by carbon dioxide.

    • Water cannot be measured using a measuring cylinder.

    • Water is not needed for photosynthesis, only for respiration.

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    3a2 marks

    Higher Tier Only

    A gardener is setting up his greenhouse.

    He is given advice from two friends on the correct conditions for his greenhouse to grow the most vegetables.

    Friend X suggested that he provide plenty of water to his vegetables but should cover all the windows in black card to stop the plants getting too hot.

    Friend Y suggested that he provide plenty of water and open the windows of the greenhouse but did not suggest covering them.

    Should the farmer follow the advice of friend X or friend Y?

    Explain your choice.

    3b3 marks

    Higher Tier Only

    The graph in Figure 4 shows how the rate of photosynthesis of strawberry plants is affected by changes in three limiting factors.

    Figure 4

    light-intensity-and-strawberry-plants-1

    Identify which three limiting factors were investigated to produce this graph.

    3c1 mark

    Higher Tier Only

    Finding the optimum conditions for photosynthesis will ensure that growth is maximised.

    Using Figure 4, complete the following sentences to identify which conditions gave the fastest rate of photosynthesis and therefore, the maximum growth.

    Optimum temperature would be __________

    Optimum carbon dioxide % would be __________

    Optimum light intensity would be __________

    3d2 marks

    Higher Tier Only

    A gardener used the results in Figure 4 to decide how much carbon dioxide to pump into the greenhouse.

    He decided to increase the atmospheric levels to 600 ppm rather than 700 ppm.

    Suggest why he made this decision.

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    4a1 mark

    A student set up an investigation into the limiting factors of photosynthesis.

    His set up is shown in Figure 5 below:

    Figure 5

    photosynthesis-prac-1

    Identify the limiting factor being investigated in this practical.

    4b2 marks

    The student carried out an investigation to find out the effect of light intensity on the rate of photosynthesis by moving the light source further and further away from the aquatic plant and counting the bubbles produced per minute at each distance.

    The results can be seen in Table 1 below:

    Table 1

    Distance between the aquatic plant and lamp in cm Number of bubbles counted in 1 minute
    0 29
    10 21
    20 45
    30 15
    40 10

    One of the results recorded was an anomaly.

    Identify which result was anomalous and explain your choice.

    4c1 mark

    Describe the trend shown by the data in Table 1.

    4d1 mark

    The student evaluated his method and decided that counting bubbles is an inaccurate way of measuring the rate of photosynthesis for two reasons.

    1. It does not take into account the fact that there may be bubbles of different sizes
    2. Tiny bubbles may be hard to see and so may not be counted at all

    Suggest a more accurate method which could be used to collect information about the amount of oxygen gas produced as the aquatic plant photosynthesizes.

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    5a1 mark

    Identify one molecule which can be synthesized using glucose produced in photosynthesis.

    5b1 mark

    Which cellular process reacts glucose with oxygen to release energy to drive other cell processes?

    5c2 marks

    A student wanted to show the starch content of a leaf. He carried out the following procedure:

    1. Take a leaf from a photosynthesising plant
    2. Boil the leaf in water
    3. Place the leaf in ethanol for 10 minutes
    4. Wash the leaf in water
    5. Place the leaf on a white tile
    6. Add several drops of iodine and observe the colour change

    Complete the table to show what colour change the student should expect to see:

    Colour of the iodine at the start

    Colour after being applied to the leaf

       

    5d1 mark

    Which of the following statements could explain the result identified in Question 5c? 

    • Glucose produced in photosynthesis has been stored as starch in the leaf

    • The plant has been carrying out transpiration so the leaves lack starch

    • Starch has been made in the leaf during the process of respiration

    • Glucose is stored as starch to be used protein synthesis

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    1a2 marks

    Green plants and algae synthesise glucose. Energy is required for this process.

    Where do plants get this energy from?

    1b3 marks

    Plants store some of the glucose that they produce in the form of starch.

    Give three other ways in which plants use glucose.

    1c3 marks

    Starch is a polymer of glucose which is stored in the roots of many plants.

    Explain as fully as you can, why it is advantageous to the plants to store carbohydrates as starch rather than as sugar.

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    2a3 marks

    Write out the full word equation for photosynthesis.

    2b5 marks

    Higher Tier Only

    Several environmental factors can affect the rate of photosynthesis, including temperature and the availability of water.

    Describe and explain the effects of two other factors that affect the rate of photosynthesis.

    You should include one or more sketch graphs in your answer.

    2c3 marks

    Plants growing in soils lacking magnesium ions do not grow to their full potential.

    Suggest why this is the case.

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    3a3 marks

    A group of students wanted to investigate how the rate of photosynthesis is affected by temperature.

    They grew some tomato plants in a greenhouse on school grounds then cut disks from the leaves of the plants in their experiments.

    To show the rate of photosynthesis, the students measured the rate of carbon dioxide uptake by the leaf disks.

    In the dark, the leaf disks did not take up any carbon dioxide, but did produce it.

    Explain this observation.

    3b2 marks

    In their investigation, the scientists measure the rate of carbon dioxide taken in by the leaf discs in the light.

    The scientists then measured the rate of carbon dioxide produced by the leaf discs when they were placed in the dark.

    The graph in Figure 1 shows the effect of temperature on:

    • Carbon dioxide uptake in the light
    • Carbon dioxide uptake in the light added to carbon dioxide production in the dark

    Figure 1

    q3b-carbon-dioxide-and-light

    Use the information in Figure 1 to describe the effect of temperature on carbon dioxide uptake in the light.

    3c2 marks

    Explain the effect of temperature on carbon dioxide uptake in the light when the temperature is increased from 20 °C to 35 °C and then from 45 °C to 50 °C.

    3d3 marks

    Higher Tier Only

    The students want to maximise the rate of growth of their tomatoes.

    Suggest the best temperature that they should heat their greenhouse to, and give a reason for your suggestion.

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    4a4 marks

    The image in Figure 1 shows some strawberry plants growing in a greenhouse on a hot sunny day in August.

    Figure 1

    greenhouse-q4a

    Identify one limiting factor that will affect the rate of photosynthesis at this time?

    Explain your answer.

    4b3 marks

    Higher Tier Only

    The rate at which plants grow can be altered by changing the conditions in which they grow.

    A propagator is a container in which the temperature, light intensity and carbon dioxide concentration can be controlled.

    The graph in Figure 2 shows the effects of changing these factors on the growth of strawberry plants.

    Figure 2

    light-intensity-and-strawberry-plants-q4b

    Describe and explain the impact of increasing carbon dioxide concentration on the mean mass of strawberry plants at bright light and 20 °C.

    4c2 marks

    Higher Tier Only

    Farmers wish to make as much profit as they can from their crops. 

    What do farmers need to consider before making decisions about the best growing conditions for their plants?

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    5a2 marks

    A typical food chain in the Pacific Ocean is: 

    phytoplankton → zooplankton → sardines → tuna 

    Figure 1 shows how a number of factors in the ocean change across the year. 

    Figure 1

    phytoplankton-population-5a

    Light intensity is a major factor in controlling the number of phytoplankton. 

    Explain why. 

    5b2 marks

    Using the information from Figure 1, suggest two reasons why the population of phytoplankton decreases between summer and autumn.

    5c2 marks

    During the summer, over a 24 hour period, the mean total amount of carbon dioxide taken in by the phytoplankton is greater than the total amount of carbon dioxide released.

    Explain why this is important for the phytoplankton.

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    1a1 mark

    Explain how autotrophs are different from heterotrophs.

    1b3 marks

    A student wanted to set up an investigation to show that photosynthesis requires carbon dioxide.

    The method they followed can be seen below:

    1. De-starch 2 plants of the same species and size
    2. Place each plant under a bell jar (bell jars A and B)
    3. Put NaHCO3 in bell jar A with the first plant
    4. Put NaOH solution in bell jar B with the second plant.
    5. Place a bung with delivery tubes in the top of bell jar A and B to allow an airflow
    6. Add some soda lime to the inlet tube of jar B
    7. Put the apparatus in full sunlight and leave for 24 hours.
    8. Observe the results of the investigation.

    The set up described in points 2 to 6 can be as seen in Figure 1.

    Figure 1
    carbon-dioxide-and-photosynthesis-1

    The independent variable in the investigation is the presence or absence of carbon dioxide.

    Suggest how stages 3, 4 and 6 allow the student to test the independent variable.

    1c3 marks

    Stage 1 of the method described in part (b) refers to 'de-starching' the plants.

    Describe how a plant may be de-starched and explain the purpose of de-starching in stage 1.

    1d5 marks

    Before the student completed the investigation described in part (b), he made the following prediction:

    'The plant in bell jar B will not photosynthesize'

    After the investigation was complete, the student observed the plants but noted no fundamental differences in their visible appearance.

    Describe another method that the student should use to show that the plant in bell jar A had photosynthesized whereas the plant in bell jar B had not.

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    2a
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    2 marks

    An investigation was carried out to test the effect of temperature on the rate of photosynthesis of pondweed.

    The volume of oxygen produced per hour was measured. The results can be seen in Table 1.

    Table 1

    temp-and-photosynthesis

    Calculate the mean rate of photosynthesis per hour when the temperature was 45 °C.

    2b
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    5 marks

    Plot the results from Table 1 onto an appropriate graph using the graph paper in Figure 2.

    Figure 2

    graph-paper-1

    2c4 marks

    Describe and explain the results shown in the graph.

    2d4 marks

    Higher Tier Only

    A farmer growing strawberries in his greenhouse used the results in Table 1 to decide on the best temperature for his greenhouse. He decided to heat the greenhouse to 30 °C.

    When the farmer measured the rate of photosynthesis of his plants, he found the rate to be 11.5% slower than the data suggested.

    Calculate the rate of photosynthesis that the farmer actually achieved at 30 °C.

    2e2 marks

    Higher Tier Only

    Suggest why the farmer may not have achieved a rate of photosynthesis as high as the data in Figure 2 predicted.

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    3a1 mark

    Higher Tier Only

    Scientists have predicted that the weather conditions of a particular mountainous region will be influenced by global warming over the next 50 years with two potential key outcomes:

    1. An increase in average summer temperatures from approximately 20 to 22 °C
    2. An increase in cloud cover

    What effect will this change in climate have on the growth of plants in that region.

    • Respiration increases, photosynthesis increases, growth increases

    • Respiration decreases, photosynthesis increases, growth increases

    • Respiration increases, photosynthesis decreases, growth decreases

    • Respiration decreases, photosynthesis increases, growth decreases

    3b6 marks

    Higher Tier Only

    Figure 3 shows the effect of several different factors on the growth of tomato plants in a greenhouse.

    Figure 3

    limiting-factors-and-photosynthesis-2

    Describe and explain how temperature and light intensity, as recorded in Figure 3, affect the rate of photosynthesis of the tomato plants.

    3c2 marks

    Higher Tier Only

    With reference to Figure 3, which factors are limiting the rate of photosynthesis between points X and Y?

    3d4 marks

    Higher Tier Only

    On a summer day, the tomato plants in the greenhouse will require a greater amount of water.

    However, even if extra water is not provided, water is unlikely to become a limiting factor of photosynthesis.

    Explain how this is possible.

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    4a6 marks

    Plan an investigation to show how the rate of photosynthesis in pond plants is affected by changes in light intensity.

    You should include detail of the independent, dependent and control variables in your investigation.

    4b5 marks

    The student carried out another investigation into the effect of soil magnesium on plant growth.

    In this investigation, the student set up three environments as follows:

    1. One plant was grown in sterile soil, provided with distilled water and placed in bright light.
    2. One plant was grown in sterile soil, provided with magnesium dissolved in distilled water and placed in bright light.

    Predict what the student will have observed after two weeks of growing in these conditions. Explain your prediction.

    4c2 marks

    When selecting the plants for the investigation in part (b), the student made sure that they picked plants with the same number of leaves.

    Explain why this was necessary.

    4d2 marks

    One method that can be used to show that photosynthesis has occurred is to test the leaves with iodine.

    Explain how this shows that photosynthesis has occurred.

    4e2 marks

    Explain the benefit of storing glucose as starch in the plant.

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    5a
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    2 marks

    Figure 4 shows the changes in carbon dioxide uptake and release over a 24 hour period in a tomato plant.

    Figure 4

    carbon-dioxide-over-24hrs-1

    Explain what the graph shows at 7:30 and 19:30.

    5b
    Sme Calculator
    3 marks

    Calculate the percentage decrease in carbon dioxide uptake between 15:00 and 18:00 in Figure 4.

    5c4 marks

    Higher Tier Only

    With reference to the amount of carbon dioxide released and taken in, Figure 4 can be used to indicate how the rate of photosynthesis changes throughout the 24 hour period, assuming that the rate of respiration is constant during this time.

    Explain how interactions between temperature and light intensity contribute towards the changes in photosynthesis represented in Figure 4.

    5d2 marks

    Over 24 hours, the tomato plant takes in more carbon dioxide than it releases.

    Explain the value of this to the tomato plant.

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