chap 10 II

chap 10 II - 1. list the components of a photosystem and...

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1. list the components of a photosystem and explain their functions Photosystems are light harvesting complexes located in the thylakoid membrane. There are two separate photosystems: Photosystem I uses pigments that absorb light with a wavelength of 700 and Photosystem II includes chlorophyll that has a peak absorption spectrum of 680. Each photosystem maintains the same elements because they both carry out the same functions. The reaction center is composed of a pair of chlorophyll a molecules plus a primary electron acceptor. The chlorophyll a molecule loses one of its electrons to the electron acceptor as light drives the electron to a higher energy state. This light is harvested by an antenna-complex, which consists of a few hundred chlorophylls and carotenoid molecules. These antenna molecules absorb photons, which are then transferred to chlorophyll a in the reaction center. 2. Trace the electron flow through photosystems II and I for the non-cyclic Electrons enter the light reaction cycle when an enzyme extracts electrons from water and supplies them to Photosystem II (P680). These electrons replace the hole that the chlorophyll molecules in the Photosystem lost when they absorbed the light. The absorbed light is what propels the electrons to an excited state as they jump up to the primary electron acceptor. The electrons then continue down the Electron Transport chain through plastoquinine, cytochrome BF complex and plastocyanin. The electrons then reach Photosystem I (P700) where, once again, light excites the electrons in the Photosystem to the final electron acceptor. The electrons then cascade down the electron transport chain through ferredoxin. The electrons are the transferred from ferredoxin to NADP+ reductase, which transfers the electrons to create NADPH. 3. When the concentration of NADPH is higher than the concentration of NADP+, cyclic electron flow occurs. Is O2 produced in this process? Explain. Is NADPH produced? Explain. What is the purpose of this cyclic electron flow? When the concentration of NADPH is higher than the concentration of NADP+, noncyclic photosynthesis is inhibited and becomes cyclic. This change of cycle occurs to the backlog of product, NADPH and excess of componential parts, NADP+. Cyclic photosynthesis only uses Photosystem I and an electron transport chain composed of ferredoxin and plastocyanin. The electrons located in the chlorophyll of Photosystem I create an H+ gradient and chemiosmosis occurs in order to produce ATP. This ATP then helps to drive photosynthesis more efficiently and enable noncyclic
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chap 10 II - 1. list the components of a photosystem and...

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