Question 1 Hard
Plants make cellulose from glucose. What is cellulose used for?
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Answer: cell walls
- It is a strong fibre.
- It is used for cell walls.
Photosynthesis and limiting factors: GCSE Combined Science Biology practice questions
A second set of questions on photosynthesis and limiting factors. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Hard
Glucose and nitrate ions are used to make which type of molecule?
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Answer: amino acids
- Nitrogen is needed for amino acids.
- They are built into proteins.
Question 3 Hard
A lamp is moved from 40 cm to 20 cm from a plant. By what factor does the light intensity increase? Give the number.
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Answer: 4
- Halving the distance squares: 2² = 4.
- The intensity is four times greater.
Question 4 Hard
A greenhouse has strong light and is warm. A grower adds carbon dioxide and the growth rate rises. Name the limiting factor that was increased.
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Answer: carbon dioxide
- Light and warmth were not limiting.
- Carbon dioxide was limiting.
Question 5 Easy
Name the sugar that plants make in photosynthesis.
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Answer: glucose
- Photosynthesis makes a sugar.
- The sugar is glucose.
Question 6 Easy
Name the tiny holes in a leaf that let carbon dioxide in.
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Answer: stomata
- Gases enter through small holes.
- They are called stomata.
Question 7 Medium
Which type of energy does chlorophyll absorb?
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Answer: light
- Plants need an energy source.
- Chlorophyll absorbs light energy.
Question 8 Medium
In the pondweed practical, which chemical is added to the water to keep the carbon dioxide concentration the same?
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Answer: sodium hydrogencarbonate
- The water needs a steady supply of carbon dioxide.
- Sodium hydrogencarbonate is added.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is the word equation for photosynthesis?
Show answer
carbon dioxide + water → glucose + oxygen.
Check 2
What is the symbol equation for photosynthesis?
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6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Check 3
Is photosynthesis exothermic or endothermic?
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Endothermic. It takes in energy from light.
Check 4
Where does photosynthesis happen in a cell?
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In the chloroplasts.
Check 5
What does chlorophyll do?
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It absorbs light energy for photosynthesis.
Check 6
Name three uses of glucose in a plant.
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Respiration, making starch for storage and making cellulose.
Check 7
What is glucose combined with to make proteins?
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Nitrate ions, to make amino acids.
Check 8
Why is starch a good storage molecule?
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It is insoluble, so it does not affect osmosis.
Check 9
What is a limiting factor?
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The factor in shortest supply that limits the rate of a process.
Check 10
Name three limiting factors of photosynthesis.
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Light intensity, carbon dioxide concentration and temperature.
Check 11
What happens to the rate at a very high temperature?
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It falls, because the enzymes are denatured.
Check 12
What does the inverse square law say about light?
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Light intensity is proportional to 1 ÷ distance².
Check 13
What happens to light intensity if the distance doubles?
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It falls to a quarter.
Check 14
How can bubbles show the rate of photosynthesis in pondweed?
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They are oxygen. More bubbles per minute means a faster rate.
Check 15
How do growers increase photosynthesis in greenhouses?
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Add light, heat and carbon dioxide.
Check 16
Why must growers weigh up costs in a greenhouse?
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The cost of heating or lighting must be less than the profit from the extra growth.
Check 17
What sugar is made in photosynthesis?
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Glucose.
Check 18
What are the raw materials of photosynthesis?
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Carbon dioxide and water.
Check 19
What are the products of photosynthesis?
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Glucose and oxygen.
Check 20
How does carbon dioxide get into a leaf?
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Through the stomata.
Check 21
How does water reach the leaves?
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It is taken up by the roots and carried up the xylem.
Check 22
What is chlorophyll?
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A green pigment in chloroplasts that absorbs light energy.
Check 23
What does the plant use cellulose for?
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To make strong cell walls.
Check 24
Why do plants make fats and oils from glucose?
Show answer
To store energy in seeds.
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