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Exam questions · Biology · Photosynthesis

The Photosynthetic Reaction

  • 9 exam questions
  • 25 marks
  • 10 quick checks
  1. 1 State [1 mark]

    Name the two products of photosynthesis.

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    Model answer

    Glucose and oxygen.

    Mark scheme

    • Glucose and oxygen — 1 mark
  2. 2 Name [3 marks]

    Figure 1 shows the substances involved in photosynthesis. Name the substances or energy shown at A, B and C.

    A leaf with three arrows marked A, B and C.
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    Model answer

    A is light (energy). B is carbon dioxide. C is oxygen.

    Mark scheme

    • A: light — 1 mark
    • B: carbon dioxide — 1 mark
    • C: oxygen — 1 mark
  3. 3 Write [2 marks]

    Write the word equation for photosynthesis.

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    Model answer

    Carbon dioxide + water makes glucose + oxygen (in the presence of light).

    Mark scheme

    • Carbon dioxide + water as reactants — 1 mark
    • Glucose + oxygen as products — 1 mark
  4. 4 Explain [2 marks]

    Explain why photosynthesis is an endothermic reaction.

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    Model answer

    It takes in energy from the surroundings. The energy is transferred from the environment to the chloroplasts by light.

    Mark scheme

    • Takes in energy — 1 mark
    • From light, absorbed by the chloroplasts — 1 mark
  5. 5 Describe [3 marks]

    Describe how a leaf is adapted to absorb carbon dioxide and light for photosynthesis.

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    Model answer

    The leaf is broad and flat, which gives a large surface area for light. The palisade cells contain many chloroplasts with chlorophyll to absorb light. Stomata let carbon dioxide diffuse in, and there are air spaces inside the leaf, so it reaches the cells.

    Mark scheme

    • Large surface area — 1 mark
    • Chloroplasts and chlorophyll absorb light — 1 mark
    • Stomata and air spaces for carbon dioxide — 1 mark
  6. 6 Describe [4 marks]

    Describe how you would test a leaf for starch.

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    Model answer

    Dip the leaf in boiling water to kill it. Heat it in hot ethanol in a water bath to remove the chlorophyll. Rinse it in warm water. Add iodine solution. If starch is present, the iodine turns from orange-brown to blue-black.

    Mark scheme

    • Boiling water to kill the leaf — 1 mark
    • Hot ethanol to remove chlorophyll — 1 mark
    • Add iodine solution — 1 mark
    • Blue-black means starch is present — 1 mark
  7. 7 Explain [4 marks]

    Explain why plants are important to nearly all other living things.

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    Model answer

    Plants make their own food by photosynthesis, so they are producers. The glucose they make, and the substances made from it, form the food that animals eat. Plants also release oxygen as a product, which animals use for aerobic respiration.

    Mark scheme

    • Plants are producers — 1 mark
    • Make glucose / food by photosynthesis — 1 mark
    • Animals eat plants or things that eat plants — 1 mark
    • Release oxygen used in respiration — 1 mark
  8. 8 Explain [3 marks]

    Explain why photosynthetic organisms are important for life on Earth.

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    Model answer

    They are producers that make organic compounds, including glucose, from carbon dioxide and water, using light energy. These compounds make up their biomass, which is the food for other organisms in the food chain. They also release oxygen.

    Mark scheme

    • They make organic compounds by photosynthesis — 1 mark
    • Their biomass is the food for other organisms — 1 mark
    • They release oxygen — 1 mark
  9. 9 Describe [3 marks]

    Describe the two stages of photosynthesis.

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    Model answer

    In the first stage chlorophyll absorbs light energy, which is used to split water into hydrogen and oxygen. In the second stage the hydrogen is used to fix carbon dioxide. This makes glucose.

    Mark scheme

    • Light energy absorbed, used to split water — 1 mark
    • Hydrogen used to fix carbon dioxide — 1 mark
    • To make glucose — 1 mark

Quick check

  1. 1

    Which gas is a reactant in photosynthesis?

    1. AOxygen
    2. BCarbon dioxide
    3. CNitrogen
    4. DHydrogen
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    B: Carbon dioxide

    Carbon dioxide is taken in and used to make glucose.

  2. 2

    Which substance is made by photosynthesis?

    1. ACarbon dioxide
    2. BWater
    3. CGlucose
    4. DChlorophyll
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    C: Glucose

    Glucose and oxygen are the products of photosynthesis.

  3. 3

    What type of reaction is photosynthesis?

    1. AExothermic
    2. BNeutral
    3. CCombustion
    4. DEndothermic
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    D: Endothermic

    Photosynthesis takes in energy from the surroundings, so it is endothermic.

  4. 4

    Where does photosynthesis take place?

    1. AIn the chloroplasts
    2. BIn the nucleus
    3. CIn the mitochondria
    4. DIn the cell wall
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    A: In the chloroplasts

    Photosynthesis takes place in the chloroplasts.

  5. 5

    Which pigment absorbs light for photosynthesis?

    1. AHaemoglobin
    2. BChlorophyll
    3. CMelanin
    4. DIodine
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    B: Chlorophyll

    Chlorophyll absorbs light energy.

  6. 6

    How does water reach the leaf?

    1. AThrough the stomata
    2. BThrough the phloem
    3. CThrough the xylem
    4. DThrough the cuticle
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    C: Through the xylem

    Water is taken up by the roots and carried up the xylem.

  7. 7

    What colour does iodine turn in the presence of starch?

    1. ARed
    2. BGreen
    3. CYellow
    4. DBlue-black
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    D: Blue-black

    Starch turns iodine from orange-brown to blue-black.

  8. 8

    Which of these is the symbol equation for photosynthesis?

    1. A6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
    2. BC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
    3. CC₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
    4. D6O₂ + 6H₂O → C₆H₁₂O₆ + 6CO₂
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    A: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

    Photosynthesis makes glucose and oxygen from carbon dioxide and water.

  9. 9

    What happens to water in the first stage of photosynthesis?

    1. AIt is made into glucose
    2. BIt is used to make chlorophyll
    3. CIt is split into hydrogen and oxygen
    4. DIt is released as a product
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    C: It is split into hydrogen and oxygen

    Light energy is used to split water into hydrogen and oxygen.

  10. 10

    What is biomass?

    1. AThe mass of living material
    2. BThe mass of water in a plant
    3. CThe oxygen released by plants
    4. DThe energy in a food chain
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    A: The mass of living material

    Biomass is the mass of living material.