# A student leaves a healthy green plant in a dark cupboard for 48 hours. After this time, the student tests a leaf from the plant for starch and finds no starch is present. The student then moves the plant to a sunny windowsill for 6 hours. A leaf tested at the end of this period gives a positive result for starch. Explain why starch is absent after the dark period and why starch is present after the plant has been placed in sunlight.

> Pearson Edexcel A-Level Biology A (9BI0) — 3.1 Photosynthesis · Explain · 5 marks

## Mark scheme (5 marks)

1. In the dark, photosynthesis cannot occur / stops
2. Because light is a raw material / required for photosynthesis (so no glucose is produced)
3. Any existing starch / glucose is used up by respiration during the dark period
4. In sunlight, photosynthesis occurs / the plant uses light energy, carbon dioxide and water to produce glucose
5. Glucose is converted to / stored as starch in the leaf

## Key terms

- [starch](https://www.gradenine.co.uk/glossary/starch)

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-leaves-a-healthy-green-fb3baae5) · Published by Druglandscape Ltd.