This set covers the skills in plant nutrition: photosynthesis inputs and products, limiting-factor graphs, leaf structure, evidence-based conclusions and mineral uptake. The questions go from easier recall to harder multi-step explanation.
Write your answer first, then open the answer. All data are invented for practice. You can log errors in the mistake log and retest queue as you go.
Questions
Q1 (recall). Complete the word equation for photosynthesis: carbon dioxide + ______ → ______ + ______. Name the energy source and the pigment that absorbs it.
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carbon dioxide + water → glucose + oxygen. The energy source is light, absorbed by chlorophyll in the chloroplasts.
Q2 (recall). Which two gases pass through the stomata as a result of photosynthesis? State the direction of each.
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Carbon dioxide enters and oxygen leaves by diffusion through the stomata. Water vapour can also be lost through them.
Q3 (calculation). Use 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. How many oxygen atoms are on the left-hand side? How many on the right? What does this show?
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Left: 6CO₂ has 6 × 2 = 12 oxygen atoms and 6H₂O has 6 × 1 = 6, total 18. Right: C₆H₁₂O₆ has 6 and 6O₂ has 12, total 18. The equation is balanced.
Q4 (calculation). A plant makes 4 glucose molecules. How many carbon dioxide molecules does it use, and how many oxygen molecules does it release?
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Each glucose needs 6 carbon dioxide and releases 6 oxygen. So 4 × 6 = 24 carbon dioxide used and 24 oxygen released.
Q5 (graph). Invented data: rate of oxygen release (bubbles per minute) at two temperatures.
| Light intensity | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| 20 °C | 0 | 5 | 10 | 15 | 15 | 15 |
| 30 °C | 0 | 5 | 10 | 15 | 20 | 20 |
What limits the rate at 20 °C at intensity 4? Give the evidence.
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At 20 °C the rate is flat at 15 from intensity 3. At 30 °C the rate at intensity 4 is 20, so a higher temperature raised it by 5. Temperature is limiting at 20 °C, because light has increased without changing the rate.
Q6 (graph). Using Q5, calculate the rate of increase per unit light intensity on the rising part, and the percentage increase in rate at intensity 4 when temperature rises from 20 °C to 30 °C.
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Rising part: 15 bubbles over 3 units = 5 bubbles per unit. Percentage increase: (20 − 15) ÷ 15 × 100 = 5 ÷ 15 × 100 = 33% (to the nearest whole number).
Q7 (explain). Explain how the palisade mesophyll is adapted for photosynthesis.
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The cells are tall and packed close to the upper surface, where most light arrives, so light is absorbed efficiently. They contain many chloroplasts with chlorophyll, so they absorb a lot of light energy. Together this means a high rate of photosynthesis per area of leaf.
Q8 (explain). A plant in a dry spell closes its stomata. State one benefit and one drawback for the plant.
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Benefit: less water vapour is lost by evaporation. Drawback: less carbon dioxide enters, so photosynthesis slows and carbon dioxide can become the limiting factor.
Q9 (evidence). A student counts bubbles per minute with a lamp placed at two distances. At 10 cm the three repeats are 22, 24 and 26. At 20 cm they are 10, 12 and 11. Find each mean, then say what the data suggest and one thing that should be controlled.
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10 cm: (22 + 24 + 26) ÷ 3 = 72 ÷ 3 = 24. 20 cm: (10 + 12 + 11) ÷ 3 = 33 ÷ 3 = 11. The rate is about 24 ÷ 11 ≈ 2.2 times higher with the closer lamp, which supports the idea that more light raises the rate. Control temperature (the lamp may warm the water), for example with a water bath.
Q10 (minerals). Seedlings in a solution without nitrate have very short stems and pale leaves. Explain why, using the job of nitrate.
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Nitrate provides nitrogen to make amino acids, which are joined to form proteins. With too little protein, cells cannot be made fast enough, so growth is stunted. Nitrate shortage also leaves the plant with less protein for enzymes and chloroplast structure, so the older leaves become pale.
If you got these wrong
Match the type of error to the lesson and fix it there:
- Q1 to Q4, mixing up substances or ratios: go to inputs and products of photosynthesis.
- Q5 and Q6, naming the limit or misreading a flat section: go to interpreting a limiting-factor graph.
- Q7 and Q8, listing features without explaining them: go to leaf adaptations for exchange.
- Q9, weak conclusions or forgetting controls: go to using evidence to test a claim.
- Q10, treating minerals as food: go to mineral uptake versus carbon acquisition.
If the same error type appears more than once, a teacher can look at your written attempts directly in online one-to-one Biology tuition.