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| Cyclic Electron Transport System |
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| Cylic reaction transport occurs only occasionally when synthesis of carbohydrate is curtailed due to limited supply of CO2 and NADPH2 starts accumulating. At this time, there would be no need for additional NADPH2. Moreover, the cyclic electron transport serves the purpose of more production of ATP where needed by the chloroplast. |
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| The cyclic electron transport pathway begins after the PS-I pigment complex absorbs solar energy. They transfer their energy to PS-I reaction centre - P700. The outer valence electron of excited P700 is raised to higher energy level which is captured by the primary acceptor of PS-I. The primary acceptor then transfers electron to ferredoxin. |
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| Reduced ferredoxin, unable to reduce NADP+ returns the electron to PS-I via cyt b6, PQ, cytf and PC. |
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| The electron transport is called cyclic because the electron emitted from PS-I returns back to PS-I passing through several intermediate carriers. |
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