Exam questions · Biology · Photosynthesis
The Photosynthetic Reaction
- 7 exam questions
- 19 marks
- 8 quick checks
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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
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2 Name [3 marks]
Figure 1 shows the substances involved in photosynthesis. Name the substances or energy shown at 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
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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
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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
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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
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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
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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
Quick check
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1
Which gas is a reactant in photosynthesis?
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B: Carbon dioxide
Carbon dioxide is taken in and used to make glucose.
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2
Which substance is made by photosynthesis?
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C: Glucose
Glucose and oxygen are the products of photosynthesis.
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3
What type of reaction is photosynthesis?
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D: Endothermic
Photosynthesis takes in energy from the surroundings, so it is endothermic.
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4
Where does photosynthesis take place?
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A: In the chloroplasts
Photosynthesis takes place in the chloroplasts.
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5
Which pigment absorbs light for photosynthesis?
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B: Chlorophyll
Chlorophyll absorbs light energy.
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6
How does water reach the leaf?
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C: Through the xylem
Water is taken up by the roots and carried up the xylem.
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7
What colour does iodine turn in the presence of starch?
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D: Blue-black
Starch turns iodine from orange-brown to blue-black.
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8
Which of these is the symbol equation for photosynthesis?
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A: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Photosynthesis makes glucose and oxygen from carbon dioxide and water.