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3.) Photosystem I
Photosystem two is the second of the two antenna complexes to engage the electrons being transferred in the photosynthetic ETC. After being passed through this complex, the electrons are transferred to FNR where they form NADPH. Clicking
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Plastocyanin then transports the two electrons to Photosystem I. Like photosystem II, the photosystem I complex contains an antenna for capturing light energy called the LHC.
Inside the photosystem I reaction center, each electron is re-engerized by the resonance energy from a photon of light. It is then transferred to ferredoxin, another mobile carrier (purple, bottom right).
Ferredoxin transfers each electron, one at a time, to Ferredoxin NADP Reductase, otherwise known as FNR (pink).
Once two electrons have been transferred to FNR, they are joined by a hydrogen ion and a molecule of NADP+. FNR then reduces NADP+ by adding to it the two electrons and one proton--creating NADPH.