BCH-9 Photosynthesis

BCH-9 Photosynthesis - PHOTOSYNTHESIS Photosynthesis takes...

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PHOTOSYNTHESIS Photosynthesis takes place in the chloroplasts of plants and in some bacteria. In thylakoids in plants, the energy of light is captured by electrons of chlorophyll molecules. The electrons are passed along an electron transport chain, a molecule of water is split and oxygen is released to the atmosphere. Protons pumped out of the thylakoid membrane drive the production of ATP. Excited electrons reduce NADP + to NADPH, and the stored energy is used to synthesize glucose in the dark in the stroma of the chloroplast.
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Where Does Photosynthesis Take Place in the Cell? – In prokaryotes such as cyanobacteria, photosynthesis takes place in granules bound to the plasma membrane. In Eukaryotes such as green plants and green algae is the chloroplast, a membrane-enclosed organelle. The chloroplast has inner and outer membranes, bodies called grana which are stacks of thylakoid disks. The stroma lies ithin the inner membrane and outside the thylakoid within the inner membrane and outside the thylakoid membrane. The trapping of light and production of oxygen takes place in the thylakoid disks. The dark reactions in which CO 2 is fixed to carbohydrates, takes place in the stroma.
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Plants contain chlorophyll a and chlorophyll b and cyanobacteria contain only chlorophyll a. Green and purple sulfur bacteria don’t use water as a reducing agent and they contain only bacteriochlorophylls. They also are anaerobic and don’t produce oxygen. The chlorophylls differ from cytochromes in structure containing magnesium rather than iron and having a phytol side chain. The absorption spectrum of a and b differ and accessory pigments can absorb light and transfer energy to chlorophylls. The light harvesting chlorophylls transfer energy along to the reaction center (a specialized chlorophyll dimer) where the chemical reactions of photosynthesis begins.
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How Are Photosystem I and II Involved in the Light Reactions of Photosynthesis? – In the light reactions, water is converted to oxygen by oxidation and NADP + is reduced to NADPH. ADP is converted to ATP by photophosphorylation. The light reactions consists of two parts; the reduction of NADP + by photosystem I (PSI) and e oxidation of water to produce oxygen by the oxidation of water to produce oxygen by photosystem II (PSII) . The production of ATP is linked to electron transport. In the dark reactions, ATP and NADPH from the light
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This note was uploaded on 12/05/2009 for the course BCH 311 taught by Professor Howlett during the Fall '08 term at Rhode Island.

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BCH-9 Photosynthesis - PHOTOSYNTHESIS Photosynthesis takes...

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