chap 10 - 1. Explain the energy transfers involved in...

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1. Explain the energy transfers involved in photosynthesis. Include a brief summary of the two main phases of photosynthesis. The light reactions are coupled with chemiosmosis to harvest NADPH and ATP. Light drives the synthesis of NADPH and ATP by energizing the both photosystem I and photosystem II. The key to this energy transformation is the flow of electrons through the photosystems and electron transport chains built into the thylakoid membrane. The NADPH and ATP from the light reactions are then donated into the Calvin cycle to produce 1,3 bisphosphoglycerate and reduction to G3P, respectively. These components continue in the cycle in order to create the final product of sugar. The light reactions convert solar energy to chemical energy of ATP and NADPH, evolving oxygen in the process. The light is sent into the photosystems. The chlorophyll at the reaction center (where the first light-driven chemical reaction occurs) of photosystem II is called P680 because its absorption spectrum has a peak of 680 nm, similarily photosystem I is called P700. Photosystem II begins photosynthesis absorbing light that is then captured by the primary electron acceptor. Water is broken down into its different components, supplying 2 electrons and emitting oxygen. The electrons are then passed down the electron transport chain composed of Pq and Pc. This exergonic fall to a lower energy level is harnessed by the thylakoid membrane to produce ATP. The electrons are now at Photosystem I where, once again, light is absorbed. The primary electron acceptor of photosystem I passes the photoexcited electrons to the second ETC, where they are transferred from Fd to NADP+. This is the redox reaction that stores the
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chap 10 - 1. Explain the energy transfers involved in...

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