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Lecture Biochemistry (2/e): Chapter 22 - Reginald Garrett, Charles Grisham

Photosynthesis is the primary source of energy for all life forms (except chemolithotrophic prokaryotes). Much of the energy of photosynthesis is used to drive the synthesis of organic molecules from atmospheric CO2. How is solar energy captured and transformed into metabolically useful chemical energy? How is the chemical energy produced by photosynthesis used to create organic molecules from carbon dioxide? | Chapter 22 Photosynthesis to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline 22.2 The Photoreactivity of Chlorophyll 22.4 The Z Scheme of Photosynthesis 22.7 Light-Driven ATP Synthesis - Photophosphorylation 22.8 Carbon Dioxide Fixation 22.9 The Calvin-Benson Cycle 22.10 Regulation of Carbon Dioxide Fixation 22.12 The C-4 Pathway of CO2 Fixation The Sun - Ultimate Energy 1.5 x 1022 kJ falls on the earth each day 1% is absorbed by photosynthetic organisms and transformed into chemical energy 6CO2 + 6H2O C6H12O6 + 6O2 1011 tons (!) of CO2 are fixed globally per year Formation of sugar from CO2 and water requires energy Sunlight is the energy source! Photosynthesis General Aspects Photosynthesis occurs in thylakoid membranes of chloroplasts - structures involving paired folds (lamellae) that stack to form "grana" The soluble portion of the chloroplast is the "stroma" The interior of the thylakoid vesicles is the "thylakoid space" or "thylakoid lumen" Chloroplasts possess DNA, RNA and ribosomes Photosynthesis Consists of Both Light Reactions and Dark Reactions The light reactions capture light energy and convert it to chemical energy in the form of reducing potential (NADPH) and ATP with evolution of oxygen The dark reactions use NADPH and ATP to drive the endergonic process of hexose sugar formation from CO2 in a series of reactions in the stroma Water is the electron donor for Photosynthetic NADP+ Reduction Equations 22.2 and 22.3 describe the light and dark reactions in green plants, respectively! Equation 22.4 provides a more general version Photosynthetic bacteria use H2S, isopropanol or other oxidizable substrates The O2 we depend upon depends in turn on large amounts of photosynthesis on the earth! Chlorophyll Photoreactive, . | Chapter 22 Photosynthesis to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline 22.2 The Photoreactivity of Chlorophyll 22.4 The Z Scheme of Photosynthesis 22.7 Light-Driven ATP Synthesis - Photophosphorylation 22.8 Carbon Dioxide Fixation 22.9 The Calvin-Benson Cycle 22.10 Regulation of Carbon Dioxide Fixation 22.12 The C-4 Pathway of CO2 Fixation The Sun - Ultimate Energy 1.5 x 1022 kJ falls on the earth each day 1% is absorbed by photosynthetic organisms and transformed into chemical energy 6CO2 + 6H2O C6H12O6 + 6O2 1011 tons (!) of CO2 are fixed globally per year Formation of sugar from CO2 and water requires energy Sunlight is the energy source! Photosynthesis General Aspects Photosynthesis occurs in thylakoid membranes of chloroplasts - structures .