Photosynthetic reaction

Photosynthesis is represented by the equation:

\(\text{carbon dioxide}+\text{water} \xrightarrow{\text{light}}\text{glucose}+\text{oxygen}\)

Students should recognise the chemical symbols: CO₂, H₂O, O₂ and C₆H₁₂O₆.

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Students should be able to describe photosynthesis as an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.

Rate of photosynthesis

Students should be able to explain the effects of temperature, light intensity, carbon dioxide concentration, and the amount of chlorophyll on the rate of photosynthesis.

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Students should be able to:
- measure and calculate rates of photosynthesis
- extract and interpret graphs of photosynthesis rate involving one limiting factor
- plot and draw appropriate graphs selecting appropriate scale for axes
- translate information between graphical and numeric form.

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These factors interact and any one of them may be the factor that limits photosynthesis.

Students should be able to explain graphs of photosynthesis rate involving two or three factors and decide which is the limiting factor.

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Students should understand and use inverse proportion – the inverse square law and light intensity in the context of photosynthesis.

Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit.

Uses of glucose from photosynthesis

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.