Biology as Poetry: Bioenergetics

Bacteriophage Ecology Group

Noncyclic Electron Flow

Description of the standard Z scheme of photosynthesis where electrons originate in photosystem II, flow through photosystem I, and end up reducing NADP+.

An outline description of the process looks like this:

     (1) Photon capture by photosystem II
     (2) Photosystem II
oxidation/e- transfer to primary electron acceptor
     (3) Energy transfer to reaction center chlorophyll
     (4) Transfer of electron to electron transport chain
     (5) Photophosphorylation
     (6) Reduction of photosystem I
     (7) Photon capture by photosystem I
     (8) Energy transfer to reaction center chlorophyll
     (9) Photosystem I oxidation/e- transfer to primary electron acceptor
     (10) NADP+ reduction producing NADH

Photosystem II is then reduced via oxidation of water, generating molecular oxygen.

Compare to cyclic electron flow:
     (9) Photosystem I oxidation/e- transfer to primary electron acceptor
     (4) Transfer of electron to electron transport chain
     (5) Photophosphorylation
     (6) Reduction of photosystem I
     (7) Photon capture by photosystem I
     (8) Energy transfer to reaction center chlorophyll
     (9) Photosystem I oxidation/e- transfer to primary electron acceptor

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