what are light and dark reactions.where do they occur in plants name the parts and full chemical equation and detail about light and dark reactions
Asked by dakmayank17 | 16th Aug, 2015, 04:16: PM
Photosynthesis takes place in two stages:
- Light reaction
- Dark reaction
- The light reaction of photosynthesis occurs only in the presence of sunlight in the thylakoid membranes of grana and stroma lamellae.
- It mainly involves absorption of sunlight by the pigments of photosystems and the conversion of their energy into usable chemical energy in the form of ATP and NADPH + H+.
- Light reaction is also called the photochemical reaction or Hill reaction or photophosphorylation.
Steps in light reaction:
- Absorption of Light
- Excitation of Reaction Centres
- Photosynthetic Electron Transport and Formation of Assimilatory Power
- The dark reaction is the second phase of photosynthesis which occurs in the stroma of chloroplasts.
- The reaction is also known as the biosynthetic phase or Blackman’s reaction or carbon dioxide fixation or Calvin cycle.
- It uses ATP and NADPH2 for the fixation and reduction of CO2 to form carbohydrates.
- The dark reaction is independent of light and may take place in the light or dark without the use of light energy.
- In the dark reaction, CO2 is reduced to carbohydrates in the form of sugar.
Steps in dark reaction:
- Carboxylation to form 3-phosphoglyceric acid (PGA).
- Reduction to form carbohydrates using ATP and NADPH
- Regeneration to form ribulose 1,5-biphosphate
Answered by Sheetal Kolte | 17th Aug, 2015, 11:14: AM
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