Agricultural Plant Biochemistry
G. Nagaraj Ex. Principal Scientist (Biochemistry) Directorate of Oilseeds Research Rajendranagar, Hyderabad - 500 030 Andhra Pradesh, India
NEW INDIA PUBLISHING AGENCY New Delhi – 110 034
NEW INDIA PUBLISHING AGENCY 101, Vikas Surya Plaza, CU Block, LSC Market Pitam Pura, New Delhi 110 034, India Phone: + 91 (11)27 34 17 17 Fax: + 91(11) 27 34 16 16 Email: info@nipabooks.com Web: www.nipabooks.com Feedback at feedbacks@nipabooks.com Š Author, 2015 ISBN: 978-93-83305-55-1
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This Book is Dedicated to The Memory of My Beloved Parents
Smt. G . Muni Laxmamma & Sri. G . Krishna Swami Naidu
Foreword
Plant biochemistry is an important emerging field in the agricultural sciences. Basic knowledge of the chemistry and the biochemical mechanisms of the plant in synthesizing various components is essential for advancements needed in other areas of agriculture like plant breeding, plant protection, plant production, etc. In the recent past, biotechnology and biochemistry are moving hand in glove to solve many problems related to humans and other living beings. Plant genetic engineering is playing a major role in tackling the quantitative and qualitative aspects of food, fodder and fertilizer. The challenges posed by the burgeoning population and dwindling land and water resources are umpteen on this earth. Plants being more efficient and environment friendly have a major role in solving many such problems. Plant production scientists need to understand the biochemical mechanisms for achieving the targets of food and fodder production. Source sink relationships need to be tackled beneficially to achieve higher productivity levels. Curtailing use of chemicals and conserving nature is another area that is engaging the attention of scientists. This book namely, “Agricultural Plant Biochemistry� is aimed at providing good information to graduate and post-graduate students in agriculture and biology. I am sure, it will also serve as a reference book to researchers in plant breeding, agronomy, plant physiology and plant
viii
Foreword
protection and will come in handy to solve many global problems by the present and future generations. Dr. G. Nagaraj has served the Indian Council of Agricultural Research, Govt. of India for over 40 years till 2006 as a scientist in Plant Biochemistry. Post-retirement, he has been active as a Fellow of the Department of Science and Technology, Govt. of India, a teacher of Biochemistry, Engineering Chemistry, Biochemical Techniques and a Consultant in Bio-energy. He has published around 300 research articles as well as a few books on oilseeds and their quality. He has vast knowledge and experience as a Biochemist. I congratulate him in his efforts and wish that this book will have wide circulation in India and abroad.
(K.S. Varaprasad) Project Director Directorate of Oilseeds Research Rajendranagar, Hyderabad-500 030, India
Preface
Plants have an important role on this globe. Being autotrophs they synthesize the most essential food components with the help of simple chemicals. They also have the ability to put together secondary nutrients, drugs and toxicants. Apart from sustaining their life, they help other forms of life including humans on this earth. They are also responsible for maintaining the climate and a congenial environment. Agriculture, which built up civilizations, has been the mainstay of human beings. Increasing population and changing needs of food with respect to quantity and quality has built up pressure to understand the biochemistry of plants and engineer them to suit to the requirements. This book is aimed at putting together the information on the various aspects of biochemistry of plants, their mechanism and utility. It has basic information and should be useful to beginners in agriculture, horticulture, biology and related disciplines. As a researcher for over forty years in agriculture, I have been collecting information on plant biochemistry. I also depended on some website and teaching material. I tried to put together most such information. I am sure the book will be useful not only to beginners, but also to some specific researchers. It should be my endevour to improve the content and quality based on expert advises.
Hyderabad May, 2014
G. Nagaraj guttarla@hotmail.com
Contents
Dedication ........................................................................................................ v Foreword ....................................................................................................... vii Preface ............................................................................................................ ix
1. Introduction ........................................................................................ 1 Biomolecules ...................................................................................................... History of biochemistry ..................................................................................... Living organisms exchange energy .................................................................. Plant biochemistry .............................................................................................
1 3 4 4
2. Carbohydrates .................................................................................... 7 Functions of carbohydrates .............................................................................. 8 Classification of carbohydrates ........................................................................ 8 Monosaccharides .............................................................................................. 9 Isomerism ......................................................................................................... 12 Oligosaccharides ............................................................................................. 18 Polysaccharides ............................................................................................... 20 Important reactions and properties of sugars ................................................ 24 Reactions of carbonyl groups ......................................................................... 24 Chain shortening and lengthening ................................................................. 25 Oxidation and reduction .................................................................................. 26 Reactions of alcoholic groups ........................................................................ 27 Uses of carbohydrates .................................................................................... 28 Monosaccharides ............................................................................................ 28 Oligosaccharides ............................................................................................. 29 Polysaccharides ............................................................................................... 29 Uses of cellulose .............................................................................................. 30
3. Lipids ................................................................................................. 31 Classification of lipids ..................................................................................... 32 Acyl glycerols .................................................................................................. 37
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Functions of lipids ........................................................................................... Properties of fatty acids .................................................................................. Properties of fats/ oils (acylglycerols) ............................................................ Rancidity of oils and fats ................................................................................. Analytical properties of lipids ......................................................................... Lipid analysis ................................................................................................... Industrial applications of acyl lipids ............................................................... Nutritional role of Lipids .................................................................................
42 43 44 44 45 47 48 49
4. Amino Acids ...................................................................................... 51 Essential amino acids ...................................................................................... Properties of amino acids ................................................................................ Reactions of amino acids ................................................................................. Separation of amino acids ...............................................................................
55 55 56 57
5. Peptides ............................................................................................. 59 Nomenclature of the peptides ......................................................................... 61 Classification of peptides based on structure ................................................ 61
6. Proteins ............................................................................................. 65 Properties of proteins ...................................................................................... Sequencing of amino acids ............................................................................. Purification techniques .................................................................................... Classification of proteins ................................................................................. Protein quality evaluation methods ................................................................
69 73 74 76 78
7. Enzymes ............................................................................................. 81 Characteristics of enzymes .............................................................................. Chemical nature of enzyme .............................................................................. Specificity of enzymes ..................................................................................... Active site ........................................................................................................ Mode of enzyme action ................................................................................... Measurement of enzyme activity .................................................................... Factors affecting enzyme activity ................................................................... Cofactors .......................................................................................................... Inhibitors .......................................................................................................... Isoenzymes ...................................................................................................... Multi-enzyme complexes ................................................................................. Allosteric enzymes ........................................................................................... Coenzymes ....................................................................................................... Classification of enzymes ................................................................................
82 83 83 84 84 87 87 91 92 94 95 95 96 97
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Regulation of enzyme activity ....................................................................... 100 Immobilization of enzymes and their uses .................................................... 100 Industrial and other application of enzymes ................................................ 101
8. Nucleic Acids .................................................................................. 105 Functions of nucleic acids ............................................................................ Components of nucleic acids ........................................................................ Functions of nucleotides ............................................................................... Structure of RNA ........................................................................................... Packing of DNA into chromosomes ..............................................................
105 106 108 115 117
9. Plant Metabolism ........................................................................... 123 Catabolism ...................................................................................................... 125 Anabolism ...................................................................................................... 127
10. Carbohydrate Metabolism ............................................................ 129 Photosynthesis .............................................................................................. Catabolism / respiration ................................................................................. Starch degradation ......................................................................................... Glycolysis ....................................................................................................... Pentose phosphate pathway (PPP) ............................................................... Energetics of pentose phosphate pathway .................................................. Significance of pentose phosphate pathway ............................................... Electron transport chain (ETC) in mitochondria ........................................... Photosystems ................................................................................................ Photolysis ...................................................................................................... Photophosphorylation .................................................................................. Factors affecting respiration .........................................................................
129 134 135 136 140 140 140 141 143 144 144 145
11. Lipid Metabolism ........................................................................... 147 Anabolism of saturated fatty acids ............................................................... Anabolism of unsaturated fatty acids .......................................................... Anabolism of triacyl glycerol ........................................................................ Catabolism of lipids ....................................................................................... Catabolism of fatty acids ...............................................................................
147 149 150 151 152
12. Amino Acid Metabolism ............................................................... 155 Biosynthesis of amino acids ......................................................................... 155 Amino acid degradation ................................................................................ 157 Ammonia assimilation .................................................................................... 159
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13. Protein Metabolism ....................................................................... 161 Translation (Protein biosynthesis) ............................................................... 163 Degradation of proteins into amino acids .................................................... 167 Ammonia assimilation .................................................................................... 168
14. Terpenes.......................................................................................... 169 Classification .................................................................................................. 170 Functions of terpenes in plants .................................................................... 170 Uses of terpenes ............................................................................................ 171
15. Phenolics ......................................................................................... 173 Some important phenolic compounds .......................................................... Classification of phenolics ............................................................................ Functions of phenolics .................................................................................. Industrial uses of phenolics .......................................................................... Cyanogenic glycosides ................................................................................. Phytic Acid ..................................................................................................... Gossypol ........................................................................................................ Phytoestrogens ..............................................................................................
173 176 176 177 177 178 178 179
16. Plant Pigments ................................................................................ 181 Chlorophyll .................................................................................................... 181 Carotenoids .................................................................................................... 183 Anthocyanins and flavonoids ...................................................................... 186
17. Sterols .............................................................................................. 189 Phytosterols ................................................................................................... 189 Steroid biosynthesis ...................................................................................... 195
18. Alkaloids.......................................................................................... 197 Nomenclature of alkaloids ............................................................................. Classification of alkaloids .............................................................................. Functions of alkaloids in plants .................................................................... Uses of alkaloids ............................................................................................ Properties of alkaloids ................................................................................... Distribution in nature .................................................................................... Some alkaloids ...............................................................................................
197 197 199 200 201 202 203
19. Vitamins ........................................................................................... 205 Classification of vitamins .............................................................................. 206 In nutrition and disease ................................................................................. 208 Deficiencies .................................................................................................... 208
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