BIOL 2905 Chapter Notes - Chapter 9.4: P700, Plastoquinone, Photosystem I
23 Oct 2017
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Light reactions in plants: photosystems ii & i are light trapping components involved in etc, electron carriers embedded in thylakoid membrane, photosystem ii, cytochrome complex, photosystem i. Steps of light reactions: absorption of light by photosystem ii results in oxidation of p680. Released electrons reduces the primary electron acceptor molecule. P680+ is returned to: from primary electron acceptor, electron passed to mobile carrier molecule plastoquinone (pq). As it accepts an electron photosystem ii, pq picks a proton from stroma. Pq diffuses through membrane before binding to cytochrome complex, at which point it donates an electron & releases a proton into the thylakoid lumen: absorption of light energy by photosystem i results in oxidation of p700. The liberated electron is used to reduce the primary acceptor before being passed down to ferredoxin. The single electron is then held by nadp+ reductase complex. P700+ is reduced back to p700 by electron that comes from plantacyanin.
