How Plants Use Glucose from Photosynthesis

Plants use glucose from photosynthesis in five main ways: for respiration, storing energy as starch, making cellulose, producing fats and oils, and making amino acids for proteins.

The five uses of glucose

1. Respiration
   Glucose is broken down during respiration to transfer energy. This energy is needed for processes such as growth and active transport. Respiration occurs continuously in living plant cells, including when there is no light.

2. Stored as starch
   Glucose is soluble, so storing a large amount of it could affect the movement of water into and out of cells. Plants convert glucose into insoluble starch for storage. The starch can later be converted back into glucose when it is needed for respiration.

3. Making cellulose
   Plants convert glucose into cellulose. Cellulose is used to make strong cell walls, which support and strengthen plant cells.

4. Making fats and oils
   Glucose can be converted into fats or oils for energy storage. These are often stored in seeds.

5. Making amino acids and proteins
   Plants combine glucose with nitrate ions absorbed from the soil to make amino acids. Amino acids are then joined together to make proteins, which are needed for growth.

In context

Photosynthesis produces glucose according to the word equation:

$$carbon\; dioxide+water\underrightarrow{light}glucose+oxygen$$

For example, some of this glucose may be used immediately in respiration, while excess glucose may be converted into starch and stored for later.

Common exam mistake

Do not say that plants absorb food from the soil. Plants make glucose by photosynthesis. They absorb water and mineral ions, including nitrate ions, from the soil.

Scope: This content is part of AQA GCSE Biology 8461 Bioenergetics and applies to both Foundation and Higher tiers.