Uses of glucose from photosynthesis — AQA GCSE Biology
Test yourself on Uses of glucose from photosynthesis with AQA GCSE practice questions.
7 days Premium · Then free forever · No card, no charge
Uses of glucose from photosynthesis explained
Glucose made in photosynthesis is not simply stored as sugar; it is used in several ways.
Read the full explanation
Some glucose is respired to release energy for the plant's life processes. Some is converted into insoluble starch, which is compact and does not affect water potential, making it ideal for storage in roots, seeds or tubers. Some glucose is converted into fats or oils for storage, especially in seeds. Some is used to make cellulose, a structural carbohydrate that strengthens cell walls. Some is combined with nitrate ions to make amino acids, which are joined to form proteins for growth and enzymes. For example, a potato tuber stores starch, while a sunflower seed stores oil.
To produce proteins, plants also use nitrate ions that are absorbed from the soil.
Plants produce glucose during photosynthesis, but also require nitrate ions absorbed from the soil to synthesise proteins. Nitrate ions are taken up by root hair cells via active transport and combined with glucose to form amino acids. These amino acids are joined together to build proteins, which are essential for plant growth and the production of new cells. Consequently, a plant suffering from nitrate deficiency exhibits stunted growth due to reduced protein synthesis. Farmers use fertilisers containing nitrates to prevent these deficiencies, ensure healthy growth and improve crop yield. (Note: chlorosis is caused by magnesium deficiency, not nitrate deficiency).
Your focus
- List the ways in which glucose produced in photosynthesis is used by a plant.
- Explain why starch is a suitable storage molecule for plants.
- Describe how glucose and nitrate ions are used to produce amino acids and proteins.
Show all 6 objectives
- State that plants absorb nitrate ions from the soil to synthesise amino acids and proteins.
- Explain why a deficiency in nitrate ions causes stunted growth in plants.
- Describe the role of active transport in the uptake of mineral ions by root hair cells.
Uses of glucose from photosynthesis exam tips
Marking Points
- Glucose is used in respiration to release energy for processes such as growth and active transport.
- Glucose is converted into insoluble starch for storage because it is compact and does not draw water into cells.
- Glucose is converted into fats or oils for storage, often in seeds, providing a concentrated energy store.
- Glucose is used to produce cellulose, which strengthens the cell wall and provides structural support.
- Glucose is used with nitrate ions to produce amino acids, which are linked to form proteins for growth and enzymes.
- Nitrate ions are absorbed from the soil by root hair cells, typically using active transport against a concentration gradient.
- Plants use glucose and nitrate ions to synthesise amino acids, which are then joined to form proteins.
- Proteins are essential for plant growth, cell repair and enzyme production.
- A lack of nitrate ions in the soil leads to stunted growth in plants due to reduced protein synthesis.
- Fertilisers can be added to nutrient-poor soil to provide essential nitrate ions and improve plant growth and crop yield.
Examiner Tips
- 💡Use the phrase 'insoluble starch' to show understanding of why it is a good storage molecule.
- 💡When asked about proteins, always mention nitrate ions as well as glucose.
- 💡Link each use of glucose to a named plant part, such as starch in potato tubers or oil in seeds.
- 💡When explaining nitrate deficiency, always link stunted growth specifically to a lack of proteins.
- 💡Always specify 'nitrate ions' rather than just 'nitrogen' when discussing what roots absorb from the soil.
Common Mistakes
- Stating that glucose is stored directly as glucose; correction: glucose is converted into insoluble starch for storage.
- Confusing cellulose with starch; correction: cellulose is a structural carbohydrate in cell walls, while starch is a storage carbohydrate.
- Forgetting that amino acid production requires nitrate ions; correction: nitrate ions absorbed from the soil are needed to make amino acids.
- Attributing yellow leaves (chlorosis) to a lack of nitrates; correction: yellowing is caused by a lack of magnesium, whereas nitrate deficiency causes stunted growth.
- Stating that plants absorb nitrogen gas directly from the air; correction: plants must absorb nitrogen in the form of nitrate ions from the soil.
- Confusing nitrate ions (NO3-) with nitrite ions (NO2-); correction: plants primarily absorb and use nitrate ions from the soil to build amino acids.