B2.3.1 Photosynthesis (part 1)
Photosynthesis is summarised by the equation:
carbon dioxide + water ➞ glucose + oxygen
1. Light energy is absorbed by a green substance called chlorophyll, which is found in chloroplasts in some plant cells and algae.
2. This energy is used by converting carbon dioxide (from the air) and water (from the soil) into sugar (glucose).
3. Oxygen is released as a by-product.
The rate of photosynthesis may be limited by:
- shortage of light
- low temperature
- shortage of carbon dioxide.
B2.3.1 Photosynthesis (part 2)
Light, temperature and the availability of carbon dioxide interact and in practice any one of them may be the factor that limits photosynthesis.
The glucose produced in photosynthesis may be converted into insoluble starch for storage. Plant cells use some of the glucose produced during photosynthesis for respiration.
Some glucose in plants and algae is used:
- to produce fat or oil for storage
- to produce cellulose - strengthens the cell wall
- to produce proteins.
To produce proteins, plants also use nitrate ions that are absorbed from the soil.