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- Dec 2021
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bio.libretexts.org bio.libretexts.org
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Photosystems consist of a light-harvesting complex and a reaction center. Pigments in the light-harvesting complex pass light energy to two special chlorophyll a molecules in the reaction center. The light excites an electron from the chlorophyll a pair, which passes to the primary electron acceptor. The excited electron must then be replaced. In photosystem II, the electron comes from the splitting of water, which releases oxygen as a waste product. In photosystem I, the electron comes from the chloroplast electron transport chain.
Photosystem 2 focuses on ATP and hydrolysis while photosystem 1 focuses on the synthesis of NADPH. Shortly after the light harvesting complex receives the light, it passes the energy to two special chlorophyll in the reaction center. The light excites an electron from the chlorophyll which then passes to the primary electron acceptor. Due to the electrons need to be replaced, photosystem 2 occurs when the synthesis of ATP and hydrolysis happen in order to get an electron. Then photosystem 1 makes an electron from the electron transport train in the chloroplast.
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