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Photosynthesis

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Photosynthesis makes the food that almost every food chain depends on.

The equation

carbon dioxide + water → glucose + oxygen (using light energy)
6CO2 + 6H2O → C6H12O6 + 6O2
It happens in chloroplasts, which contain green chlorophyll that absorbs light.

Endothermic

Photosynthesis is endothermic: it takes in energy from the environment, as light.

Uses of glucose

Respiration, making starch for storage, cellulose for cell walls, proteins (with nitrate ions), and fats and oils for storage.
Worked example

Why do plants need light for photosynthesis?

  1. Light provides the energy for the reaction.
  2. Chlorophyll absorbs it.

Answer: Light is the energy source.

Key idea

Carbon dioxide + water → glucose + oxygen, using light absorbed by chlorophyll in chloroplasts. It is endothermic. Glucose is used for respiration, starch, cellulose and proteins.

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