Uses of glucose from photosynthesisSpec 4.4.1.3
In short
The glucose made in photosynthesis is used for respiration, converted into insoluble starch for storage, used to make fat or oil for storage, used to make cellulose to strengthen cell walls, and used to make amino acids for protein synthesis. To make amino acids, plants also need nitrate ions absorbed from the soil as a source of nitrogen.
The glucose produced in photosynthesis may be:
- used for respiration
- converted into insoluble starch for storage
- used to produce fat or oil for storage
- used to produce cellulose, which strengthens the cell wall
- used to produce amino acids for protein synthesis.
To produce proteins, plants also use nitrate ions that are absorbed from the soil. Glucose alone contains only carbon, hydrogen and oxygen, so plants need nitrate ions as a source of nitrogen to make amino acids.
| Use | Product | Purpose |
|---|---|---|
| Respiration | Energy transferred | Supplies the energy for living processes |
| Storage | Starch | Insoluble, so suitable for storage |
| Storage | Fat or oil | Stored for later use |
| Cell walls | Cellulose | Strengthens the cell wall |
| Protein synthesis | Amino acids (with nitrate ions) | Used to build proteins |
Starch is stored because it is insoluble. You can test a leaf for starch with iodine solution, which turns from orange-brown to blue-black if starch is present.
Quick check
Write the word equation for photosynthesis.
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carbon dioxide + water → glucose + oxygen (in the presence of light)
Name the four factors that affect the rate of photosynthesis.
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Temperature, light intensity, carbon dioxide concentration and the amount of chlorophyll.
In the pondweed practical, what is the independent variable?
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The distance of the lamp from the pondweed (which changes the light intensity).
Why do plants need nitrate ions?
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To make proteins, as nitrate ions are used with glucose to make amino acids.
Why is photosynthesis described as endothermic?
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It takes in energy from the environment, transferred to the chloroplasts by light.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026