Explain why a plant kept in a dark cupboard for several days will eventually die, even if it is given water and minerals.

AQA A-Level Biology (7402) — 3.5.1 Photosynthesis · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

A plant needs light for photosynthesis. In the dark it cannot produce glucose.
Glucose is the substrate for cellular respiration.
Without respiration the plant cannot release energy.
Without energy it cannot carry out essential life processes.
Therefore the plant eventually dies.

Examiner tips

  • Use the exact sequence: light → photosynthesis → glucose → respiration → energy → life processes → death
  • Show the causal chain, not just list points
  • Use UK spelling (e.g., ‘processes’)
  • Mention that water and minerals are insufficient without energy

Common mistakes

  • Failing to mention that glucose is required for respiration
  • Confusing photosynthesis with respiration
  • Using vague terms like ‘energy’ without linking to respiration

Mark scheme (5 marks)

  1. Photosynthesis requires light
  2. Without light, the plant cannot produce glucose
  3. Glucose is needed as a reactant / substrate for respiration
  4. Without respiration the plant cannot release energy
  5. Without energy the plant cannot carry out essential life processes, so it dies

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