Chloroplasts

This monograph is intended to provide an overview of the structure, function, and development of the chloroplast. It should be viewed as a beginning of the study of chloroplasts and not as an end. In keeping with an introductory approach, abbreviations generally have not been used, so that substance is not replaced by symbol. The principal aim has been to provide a teaching tool to introduce students to the major characteristics of the chloroplast, with as much emphasis on mech­ anisms as possible at this level. It was written for students with an advanced college level education in biology and chemistry who also have some knowl­ edge of biochemistry. The fundamentals of these subj ects cannot be included in a book of this type. However, to provide a meaningful description of how the chloroplast works, Le. , what the mechanisms of photosynthetic reactions are, the subj ect must be dealt with at the molecular level. Living systems are chemical systems, and the importance of understanding these systems at the molecular level cannot be overstated. Therefore, although attempts were made to keep the chemistry at a relatively simple level, occasionally statements are made that can be understood only with a sufficient background knowledge of chemistry. It is important for students to realize in broad outline form the functions of the chloroplast and where its functions fit into the scheme of life.

1 Historical Perspectives: The Beginnings of Research on Photosynthesis.- I. The Discovery of Chloroplasts.- II. Chemical Studies—The Development of Gas Chemistry.- III. The Phlogiston Theory.- IV. The Discovery of Photosynthesis.- V. Association of Photosynthesis with Chloroplasts.- VI. Development of a Major Research Tool—Isotopic Compounds.- VII. Summary.- Literature Cited.- Additional Reading.- 2 Structure of the Chloroplast.- I. Importance of the Membrane.- II. Structure of the Thylakoid Membrane.- III. Morphological Aspects of Photosynthetic Membranes.- IV. The Chloroplast Endoplasmic Reticulum and the Periplastidal Compartment.- V. Evolutionary Ontogeny of Chloroplast Structure.- VI. The Pyrenoid Body.- VII. Chloroplast Size and Number.- VIII. Summary.- Literature Cited.- Additional Reading.- 3 Characteristic Components of Chloroplast Membranes.- I. Purification of Chloroplasts.- II. Components of the Thylakoid Membrane.- A. Chlorophyll.- B. Carotenoid Pigments.- C. Galactosyl Diglycerides.- D. Minor Lipids.- E. Quinone Compounds.- F. Accessory Pigments.- G. Integral Membrane Proteins.- H. Chlorophyll-Protein Complexes.- I. Photosystem 1 and 2 Complexes.- J. Minor Membrane Polypeptides.- III. Components of the Chloroplast Stroma.- IV. Summary.- Literature Cited.- Additional Reading.- 4 The Process of Photosynthesis: The Light Reactions.- I. Introduction.- II. Primary Mechanisms of Photosynthesis.- III. Chemical Currency.- IV. The Flow of Electrons during Photosynthesis.- V. Membrane-Bound Electron Carriers.- A. Photosystem 2 (P680).- B. B Protein.- C. Plastoquinone.- D. Cytochromes.- E. Plastocyanin.- F. Photosystem 1 (P700).- G. Ferredoxin.- H. Ferredoxin-NADP+ Reductase.- VI. Topographical Arrangement of Electron Carriers.- VII. Evidence for Two Photosystems.- VIII. An Alternate Proposal.- IX. Regulation of Energy Distribution from Light-Harvesting Complexes by Protein Phosphorylation.- X. Formation of ATP.- XI. The Chloroplast Coupling Factor (CF1).- XII. Electron Transport in Photosynthetic Bacteria.- Additional Reading.- 5 The Process of Photosynthesis: The Dark Reactions.- I. Introduction.- II. Fixation of CO2.- A. The C3 Pathway—The Reductive Pentose-Phosphate Cycle.- B. The C4 Pathway—The Hatch-Slack Pathway.- C. The CAM Pathway.- D. The Reductive Carboxylic Acid Cycle.- III. Requirement of CO2 for O2 Evolution.- IV. Inhibition of CO2 Fixation by O2: Photorespiration.- V. Assimilation of Nitrogen and Sulfur.- VI. Summary for Chapters 4 and 5.- Literature Cited.- Additional Reading.- 6 The Chloroplast Genome and Its Expression.- I. Introduction.- 147II. Purification of Chloroplast DNA.- III. Chloroplast DNA Molecules Are Identical.- IV. Synthesis of Chloroplast DNA.- V. Inheritance of Chloroplast DNA.- VI. Expression of Chloroplast Genetic Information.- A. Chloroplast Ribosomes.- B. Transfer RNA.- C. Messenger RNA.- VII. Why Chloroplast DNA?.- VIII. Protein Synthesis.- A. Initiation.- B. Elongation.- C. Amino Acyl-tRNA Synthetases.- IX. Association of Ribosomes with Membranes.- X. Summary.- Literature Cited.- Additional Reading.- 7 Development of Chloroplasts: Structure and Function.- I. Introduction.- II. Etiolation of Chloroplasts.- III. Morphology of Chloroplast Development.- A. Higher Plants.- B. Algae.- IV. Site of Assembly of Thylakoid Membranes.- V. Chloroplast Development and the Chloroplast Endoplasmic Reticulum.- VI. Chromatophore Development in Photosynthetic Bacteria.- VII. Development of Function.- VIII. Development of Photosynthetic Units.- Additional Reading.- 8 Development of Chloroplasts: Biosynthetic Pathways and Regulation.- I. Introduction.- II. Chlorophyll.- A. Pathway of Biosynthesis.- B. Regulation of Chlorophyll Synthesis.- III. Lipids.- IV. Synthesis of Chloroplast Proteins.- A. Ribulose 1,5-Bisphosphate Carboxylase.- B. Regulation of Subunit Production.- C. Thylakoid Membrane Polypeptides.- D. Regulation of Assembly of the Chlorophyll a/b-Protein Complex.- V. How Are Polypeptides Taken up by Chloroplasts?.- VI. Processing of Incoming Chloroplast Proteins.- VII. Source of Chloroplast Proteins—A Summary.- VIII. Light and Chloroplast Development.- A. The Regulatory Factor Phytochrome.- B. Effects of Blue Light.- C. Are There Additional Light Receptors?.- IX. Symmary.- Literature Cited.- Additional Reading.- 9 Evolutionary Aspects of Chloroplast Development.- I. Evolutionary History of Chloroplasts.- II. Chloroplasts Resemble Prokaryotic Cells.- III. Development of Phylogenetic Trees.- IV. Was DNA Transferred from Chloroplast to Nucleus?.- V. Development of Photosynthetic Systems.- VI. Summary.- Literature Cited.- Additional Reading.