Photosynthesis Problem Set 1
Problem 11 Tutorial: Photosystem II featuresWhich of the following is NOT true of photosystem II?
Photosystem II is located in the thylakoid membranes of chloroplasts
Photosystem II is the site for oxidation of waterWhen photosystem II is excited by absorption of a photon of light energy, and expels an electron to the photosynthetic electron transport chain, the oxidized form of the reaction center chlorophyll molecule is transiently created (Chl+). This Chl+ species is a very strong oxidizing agent, and is able to accept electrons from water. Water is oxidized on the inner side of the thylakoid membrane, donating electrons to the oxidized PS II reaction center. Oxygen is released as a by product of water oxidation, and the protons released contribute to the H+ gradient used as the energy source for ATP synthesis.
Photosystem II has a special, oxidizable chlorophyll
Photosystems II and I have antenna complexes for light harvesting activity
PS II is not involved in cyclic photophosphorylationA photon of light energy absorbed by photosystem I results in the excited state P700* pigment which undergoes oxidation to P700+. Electrons are cycled from photosystem I via the photosynthetic electron transport chain back to the reaction center, where P700+ is reduced to P700. Electron transport leads to formation of a pH gradient, and ATP is produced. No reduction of NADP+ occurs; No oxidation of water occurs; It requires only photosystem I — photosystem II is not needed. Light energy used to establish pH gradient that is a chemiosmotic energy source for chloroplast ATP synthase.
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