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CBSE Class 11th Biology Notes for Chapter 13 Photosynthesis in Higher Plants

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Green plants make their own food by the process of photosynthesis. During this process, carbon dioxide from the atmosphere is taken in by leaves through stomata and used for making carbohydrates.
Photosynthesis takes place only in the green parts of the plants, mainly the leaves. Within the leaves, the mesophyll cells have a large number of chloroplasts that are responsible for carbon dioxide fixation. Photosynthesis has two states:
The light reaction
In the light reaction, the light energy is absorbed by the pigments present in the antenna, and funneled to special chlorophyll. There are two photosystems: PSI and PSII. The PSI has a 700 nm absorbing chlorophyll while PSII has a 680nm absorbing chlorophyll. After absorbing light, electrons are excited and transferred through the two photosystems and finally to NAD forming NADH.
Carbon Fixation cycle
In the carbon fixation cycle , CO2 is added by the enzyme BuBisCO, to a 5-carbon compound RuBP that is converted to 2 molecules of 3-carbon PGA. This is then converted to sugar by the Calvin cycle, and the RuBP is regenerated. During this process ATP and NADPH synthesized in the light reaction are utilized. RuBisCO also catalyses a wasteful oxygenation reaction- photorespiration.

  • Light
  • Carbon dioxide concentration
  • Temperature
  • Water

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