What is photosynthesis? Explain the mechanism.

Photosynthesis is the process by which green plants synthesize organic food as carbohydrates in the presence of sunlight, chlorophyll water, CO2 and some other raw materials. Oxygen is released in this process.

Site of photosynthesis-


Chloroplast are the organelles in the cells of green plants which contains chlorophyll.

Raw materials for photosynthesis-

  • Carbon dioxide
  • Water
  • Other materials like nitrogen Phosphorus iron and magnesium are also taken up from the soil.

Conditions necessary for photosynthesis

  • Presence of sunlight and chlorophyll are necessary for photosynthesis.
  • Sunlight– Intensity , quality and duration of sunlight affect the rate of photosynthesis.
  • Chlorophyll– A green colour photosynthetic pigment found in chloroplast of a plant that is responsible for trapping solar energy.

Mechanism of the photosynthesis is as follows

  • Absorption-Light energy is first absorbed by chlorophyll molecules found inside the chloroplasts
  • Conversion-The absorb energy causes splitting of water molecules into hydrogen and oxygen. During this process the light energy gets converted into chemical energy.
  • Reduction-Finally carbon dioxide is reduced to carbohydrate which is the end product of photosynthesis.

The above step need not take place one after the other immediately, for example desert plants take in carbon dioxide at night and prepare an intermediate compound. This intermediate compound is acted upon by the energy absorbed during the day by the chlorophyll.

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