TAILIEUCHUNG - Biochemistry, 4th Edition P68

Biochemistry, 4th Edition P68. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | How Is Solar Energy Captured by Chlorophyll 633 CO2 by a series of enzymatic reactions found in the stroma see Equation which follows . Water Is the Ultimate e Donor for Photosynthetic NADP Reduction In green plants water serves as the ultimate electron donor for the photosynthetic generation of reducing equivalents. The reaction sequence 2 H2O 2 NADP x ADP x Pi - O2 2 NADPH 2 H x ATP x H2O describes the process where nhv symbolizes light energy nis some number of photons of energy hv where h is Planck s constant and v is the frequency of the light . Light energy is necessary to make the unfavorable reduction of NADP by H2O 4 o V 219 kJ mol NADP thermodynamically favorable. Thus the light energy input nhv must exceed 219 kJ mol NADP . The stoichiometry of ATP formation depends on the pattern of photophosphorylation operating in the cell at the time and on the ATP yield in terms of the chemiosmotic ratio ATP H as we will see later. Nevertheless the stoichiometry of the metabolic pathway of CO2 fixation is certain 12 NADPH 12 H 18 ATP 6 CO2 12 H2O---- C6H12O6 12 NADP 18 ADP 18 Pi A More Generalized Equation for Photosynthesis In 1931 comparative study of photosynthesis in bacteria led van Niel to a more general formulation of the overall reaction v- i out L g y Z- . i oA i TT o CO2 T 2 H2A ----7 CHçU T 2A T H2O Hydrogen Hydrogen acceptor donor Reduced Oxidized acceptor donor In photosynthetic bacteria H2A is variously H2S photosynthetic green and purple sulfur bacteria isopropanol or some similar oxidizable substrate. CH2O symbolizes a carbohydrate unit. CO2 2 H2S--- CH2O H2O 2 S O II CO2 2 CH3 CHOH CH3---------n CH2O H2O 2 CH3 C CH3 In cyanobacteria and the eukaryotic photosynthetic cells of algae and higher plants H2A is H2O as implied earlier and 2 A is O2. The accumulation of O2 to constitute 21 of the earth s atmosphere is the direct result of eons of global oxygenic photosynthesis. How Is Solar Energy Captured by .

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