Textbook of Veterinary Physiological Chemistry (eBook)

Larry Engelking (Autor)

eBook Download: PDF | EPUB

2014 | 3. Auflage
786 Seiten
Elsevier Science (Verlag)
978-0-12-391910-6 (ISBN)

Infos

Bridging the gap between basic and clinical science concepts, the Textbook of Veterinary Physiological Chemistry, Third Edition offers broad coverage of biochemical principles for students and practitioners of veterinary medicine. The only recent biochemistry book written specifically for the veterinary field, this text covers cellular-level concepts related to whole-body physiologic processes in a reader-friendly, approachable manner. Each chapter is written in a succinct and concise style that includes an overview summary section, numerous illustrations for best comprehension of the subject matter, targeted learning objectives, and end of the chapter study questions to assess understanding.

With new illustrations and an instructor website with updated PowerPoint images, the Textbook of Veterinary Physiological Chemistry, Third Edition, proves useful to students and lecturers from diverse educational backgrounds. Sectional exams and case studies, new to this edition, extend the breadth and depth of learning resources.

• Provides newly developed case studies that demonstrate practical application of concepts
• Presents comprehensive sectional exams for self-assessment
• Delivers instructor website with updated PowerPoint images and lecture slides to enhance teaching and learning
• Employs a succinct communication style in support of quick comprehension

Larry Engelking holds B.S. and M.S. degrees in biology from Idaho State University, and a Ph.D. degree in physiology from Kansas State University. He has held post-doctoral research positions at the University of Florida Veterinary School and the University of Alabama Medical School, teaching positions at Harvard University, and professorial positions at Tufts University. With over 35 years of teaching and research experience, Dr. Engelking is an expert in the fields of biochemistry and physiology.

Inhalt

Front Cover 1
Textbook of Veterinary Physiological Chemistry 2
Copyright 3
Table of Contents 4
Acknowledgments 8
Preface to the First Edition 10
Preface to the Second Edition 11
Preface to the Third Edition 12
Section I: Amino Acid and Protein Metabolism 14
Chapter 1: Chemical Composition of Living Cells 15
Overview 15
Nucleic Acids 16
Proteins 17
Polysaccharides 18
Lipids 18
Objectives 19
Chapter 2: Properties of Amino Acids 20
Overview 20
Hydrophilic Amino Acids 22
Hydrophobic Amino Acids 22
Neither Hydrophobic nor Hydrophilic 23
Enantiomers 23
Objectives 23
Chapter 3: Amino Acid Modifications 25
Overview 25
Modified Amino Acids Found in Protein 25
Nonprotein Amino Acids 28
Essential and Nonessential Amino Acids 28
Objectives 29
Chapter 4: Protein Structure 31
Overview 31
Primary Structure 32
Secondary Structure 33
Tertiary Structure 34
Quaternary Structure 35
Protein Misfolding 35
Protein Denaturation 36
Plasma Proteins 36
Objectives 37
Chapter 5: Properties of Enzymes 39
Overview 39
General Properties of Enzymes 40
Enzyme Nomenclature 40
Coenzymes 40
Control of Enzyme Activity 40
Objectives 43
Chapter 6: Enzyme Kinetics 45
Overview 45
Substrate Saturation Curves 46
Double Reciprocal Plots 47
Enzyme Inhibitors 47
Reversible, Competitive Inhibitors 47
Reversible, Noncompetitive Inhibitors 48
Uncompetitive Inhibitors 48
Irreversible Inhibitors 48
Therapeutic Inhibitors 48
Isozymes 48
Cofactors and Coenzymes 50
Objectives 50
Chapter 7: Protein Digestion 52
Overview 52
Tissue Protein Turnover 52
Gastrointestinal Protein Digestion 53
Objectives 56
Chapter 8: Amino Acid Catabolism 58
Overview 58
Hepatic Metabolism of Phenylalanine 58
The BCAA/AAA Ratio 59
Intestine 61
Skeletal Muscle 61
Kidney 61
Liver 62
Nitrogen Balance 62
Objectives 63
Chapter 9: Transamination and Deamination Reactions 65
Overview 65
Deamination Reactions 66
Transamination Reactions 68
Other Transaminases 69
Objectives 69
Chapter 10: Urea Cycle (Krebs-Henseleit Ornithine Cycle) 71
Overview 71
Carbamoyl Phosphate Formation 72
Citrulline Formation 72
Argininosuccinate Formation 74
Arginine and Fumarate Formation 74
Urea Formation 74
Abnormalities in Urea Biosynthesis 75
Objectives 76
Chapter 11: Glutamine and Ammonia 78
Overview 78
Ammonia Toxicity 78
Nitrogen and Carbon Flux Between Liver and Kidney 78
Objectives 82
Chapter 12: Nonprotein Derivatives of Amino Acids 83
Overview 83
Tyrosine (Tyr) 83
Tryptophan (Trp) 84
Histidine (His) 84
Glutamate (Glu) 86
Glycine (Gly) 86
Arginine (Arg) 86
Lysine (Lys) 87
Aspartate (Asp) 87
Serine (Ser) 87
Objectives 87
Addendum to Section I 89
Introduction to Section II 89
Section II: Nucleotide and Nucleic Acid Metabolism 90
Chapter 13: Nucleotides 91
Overview 91
Nucleotide Structure 92
Polynucleotide Structure and Synthesis 94
Objectives 95
Chapter 14: Pyrimidine Biosynthesis 96
Overview 96
Pathway Summary 96
Pathway Regulation 98
Unusual Physical Properties of Relevant Early Stage Mammalian Enzymes 98
Objectives 100
Chapter 15: Purine Biosynthesis 101
Overview 101
Phase One - PRPP Biosynthesis 103
Phase Two - Formation of IMP (the parent NMP) 103
Phase Three - Formation of AMP, GMP, and the Respective 5'-triphosphates 103
Formation of NDP and NTP Forms of Adenine and Guanine 104
Regulation of Purine Biosynthesis 104
Objectives 105
Chapter 16: Folic Acid 106
Overview 106
Folic Acid and its Active Form, Tetrahydrofolate 106
Folate Metabolism in Animals vs Bacteria 106
THFA-mediated One-carbon Metabolism 108
Folate Plasma Concentrations 108
Megaloblastic Anemia (MA) 108
Formation of Deoxyribonucleotides 109
Conversion of dUTP to its 5-methyl Form, dTTP 109
Chemotherapeutic Drug Targets in dNTP and Folate Metabolism 110
Objectives 110
Chapter 17: Nucleic Acid and Nucleotide Turnover 111
Overview 111
Release of Bases from Nucleic Acids 111
Nucleotides and Nucleosides 112
Salvage of Purine and Pyrimidine Bases 112
Degradation of Pyrimidine Bases 113
Degradation of Purine Bases 114
Excretion of Purine Degradation Products 116
Uric Acid and Health 116
Objectives 117
Sections I and II Examination Questions 118
Addendum to Section II 129
Introduction to Section III 129
Section III: Carbohydrate and Heme Metabolism 130
Chapter 18: Carbohydrate Structure 131
Overview 131
Complex Carbohydrates 131
Monosaccharides 132
Pentoses, NAD+ and NADP+, NADH and NADPH 132
Hexoses 133
Disaccharides and Trisaccharides 134
Objectives 135
Chapter 19: Polysaccharides and Carbohydrate Derivatives 137
Overview 137
Polysaccharides 137
Carbohydrate Derivatives 139
Objectives 142
Chapter 20: Glycoproteins and Glycolipids 143
Overview 143
Glycoproteins 143
Glycolipids 147
Objectives 148
Chapter 21: Overview of Carbohydrate Metabolism 149
Overview 149
Objectives 153
Chapter 22: Glucose Trapping 154
Overview 154
Objectives 158
Chapter 23: Glycogen 160
Overview 160
Glycogenesis 161
Glycogenolysis 162
Glycogen Storage Diseases 164
Objectives 165
Chapter 24: Introduction to Glycolysis (The Embden-Meyerhoff Pathway (EMP)) 166
Overview 166
Why is Anaerobic Glycolysis Necessary? 169
Historical Perspective 170
Objectives 171
Chapter 25: Initial Reactions in Anaerobic Glycolysis 172
Overview 172
Objectives 176
Chapter 26: Intermediate Reactions in Anaerobic Glycolysis 177
Overview 177
Objectives 181
Chapter 27: Metabolic Fates of Pyruvate 182
Overview 182
Objectives 185
Chapter 28: Hexose Monophosphate Shunt (HMS) 187
Overview 187
Objectives 190
Chapter 29: Uronic Acid Pathway 192
Overview 192
Objectives 196
Chapter 30: Erythrocytic Protection from O2 Toxicity 197
Overview 197
Oxygen Toxicity 197
Cellular Protection Against Free Radicals 198
Objectives 201
Chapter 31: Carbohydrate Metabolism in Erythrocytes 203
Overview 203
Objectives 206
Chapter 32: Heme Biosynthesis 208
Overview 208
Harderian Glands 211
Photodynamic Therapy (PDT) 211
Hemoglobin (Hb) 211
Anemias and Polycythemia 213
Objectives 213
Chapter 33: Heme Degradation 215
Overview 215
Hepatic Bilirubin Uptake, Conjugation, and Excretion 217
Characterization of Plasma Bilirubin 218
Objectives 220
Chapter 34: Tricarboxylic Acid (TCA) Cycle 221
Overview 221
Exchange Transporters of the Inner Mitochondrial Membrane 225
Objectives 226
Chapter 35: Leaks in the Tricarboxylic Acid (TCA) Cycle 227
Overview 227
TCA Cycle Intermediates are Converted to Other Essential Compounds 227
Replenishment of TCA Cycle Intermediates 229
Objectives 231
Chapter 36: Oxidative Phosphorylation 232
Overview 232
Movement of Electrons from Cytoplasmic NADH to the Mitochondrial ETC 232
Oxidation and Reduction 234
Phosphorylation 234
Inhibitors and Uncouplers 236
Objectives 236
Chapter 37: Gluconeogenesis 238
Overview 238
Gluconeogenic Precursors 240
Gluconeogenic Enzymes 241
Objectives 243
Chapter 38: Carbohydrate Digestion 244
Overview 244
Salivary .-Amylase (Ptyalin) 244
Intestinal Carbohydrate Digestion 245
Intestinal Monosaccharide Absorption 247
Objectives 249
Section III Examination Questions 251
Addendum to Section III 265
Introduction to Section IV 265
Section IV: Vitamins and Trace Elements 266
Chapter 39: Vitamin C 267
Overview 267
Water-soluble Vitamins 267
Objectives 272
Chapter 40: Thiamin (B1) and Riboflavin (B2) 273
Overview 273
Thiamin (Vitamin B1) 273
Riboflavin (Vitamin B2) 275
Objectives 277
Chapter 41: Niacin (B3) and Pantothenic Acid (B5) 278
Overview 278
Niacin (Vitamin B3) 278
Pantothenic Acid (Vitamin B5) 280
Lipoic acid 282
Objectives 282
Chapter 42: Biotin and Pyridoxine (B6) 284
Overview 284
Biotin 284
Pyridoxine (B6) 287
Objectives 288
Chapter 43: Cobalamin (B12) 289
Overview 289
Objectives 293
Chapter 44: Vitamin A 295
Overview 295
Fat-Soluble Vitamins 295
Vitamin A 295
Vitamin A Toxicity 297
Vitamin A and Vision 298
Vitamin A Deficiency 298
Objectives 300
Chapter 45: Vitamin D 301
Overview 301
Vitamin D Toxicity 305
Vitamin D Deficiency 305
Objectives 306
Chapter 46: Vitamin E 307
Overview 307
Vitamin E Deficiency 310
Objectives 311
Chapter 47: Vitamin K 312
Overview 312
Vitamin K Deficiency 314
Vitamin K Toxicity 316
Objectives 316
Chapter 48: Iron 317
Overview 317
Trace Elements 317
Iron (Fe) 317
Iron Toxicity 320
Iron Deficiency 320
Objectives 321
Chapter 49: Zinc 322
Overview 322
Zinc Toxicity 325
Objectives 326
Chapter 50: Copper 327
Overview 327
Copper Deficiency 330
Copper Toxicity 330
Objectives 331
Chapter 51: Manganese and Selenium 332
Overview 332
Manganese (Mn++) 332
Selenium (Se) 334
Objectives 337
Chapter 52: Iodine and Cobalt 338
Overview 338
Iodine (I) 338
Cobalt (Co) 340
Objectives 342
Section IV Examination Questions 343
Addendum to Section IV 351
Introduction to Section V 351
Section V: Lipid Metabolism 352
Chapter 53: Overview of Lipid Metabolism 353
Overview 353
Objectives 357
Chapter 54: Saturated and Unsaturated Fatty Acids 358
Overview 358
Essential Fatty Acids 360
Objectives 363
Chapter 55: Fatty Acid Oxidation 364
Overview 364
Mitochondrial ß-oxidation 367
Peroxisomal ß-oxidation 367
Objectives 369
Chapter 56: Fatty Acid Biosynthesis 371
Overview 371
Fatty Acid Elongation Beyond Palmitate 373
NADPH Generation and FattyAcid Biosynthesis 374
Objectives 376
Chapter 57: Triglycerides and Glycerophospholipids 378
Overview 378
Triglycerides 379
Glycerophospholipids 381
Objectives 384
Chapter 58: Phospholipid Degradation 385
Overview 385
Ca++ Signaling 386
Phospholipids and the Ca++ Messenger System 387
Objectives 390
Chapter 59: Sphingolipids 391
Overview 391
Sphingolipid Degradation 395
Objectives 396
Chapter 60: Lipid Digestion 397
Overview 397
Emulsification of Dietary Fat 398
Enzymatic Hydrolysis of Dietary Lipids 398
Lipid Absorption in the Small Intestine 399
Mucosal Resynthesis of Dietary Lipids 399
Abnormalities in Lipid Digestion and Absorption 400
Objectives 402
Chapter 61: Cholesterol 403
Overview 403
Cholesterol Biosynthesis 405
Abnormalities in the Plasma Cholesterol Concentration 408
Objectives 408
Chapter 62: Bile Acids 410
Overview 410
Hepatic BA Biosynthesis 412
Bile Acid Actions in Bile, and in Luminal Contents of the Intestine 414
Intestinal Bile Acid Reabsorption and Enterohepatic Cycling 415
Regulation of Hepatic Bile Acid Biosynthesis 415
Bile Acid Signaling 416
Integration of Bile Acid Signaling, Hepatic Carbohydrate and Lipid Metabolism 416
Bile Acids as Therapeutic Agents 416
Objectives 417
Chapter 63: Lipoprotein Complexes 419
Overview 419
Apoproteins 420
FFA-Albumin Complexes 421
Objectives 423
Chapter 64: Chylomicrons 424
Overview 424
Objectives 428
Chapter 65: VLDL, IDL, and LDL 429
Overview 429
Very Low-Density Lipoprotein (VLDL) 429
Intermediate-Density (IDL), and Low-Density Lipoprotein (LDL) 431
Objectives 433
Chapter 66: LDL Receptors and HDL 434
Overview 434
Nature of the Low-Density Lipoprotein (LDL) Receptor 434
High-Density Lipoprotein (HDL) 436
Objectives 438
Chapter 67: Hyperlipidemias 440
Overview 440
Treatments for the Secondary Hyperlipidemias 444
Objectives 445
Chapter 68: Eicosanoids I 447
Overview 447
Eicosanoid Degradation and Activity 449
Thromboxanes 450
Objectives 451
Chapter 69: Eicosanoids II 452
Overview 452
Hydroperoxyeicosatetraenoic Acids (HPETEs) and Hydroxyeicosatetraenoic Acids (HETEs) 452
Leukotrienes (LTs) 452
Prostaglandins (PGs) 454
Objectives 456
Chapter 70: Lipolysis 457
Overview 457
Endocrine Control of Lipolysis 458
Glyceroneogenesis 460
Satiety 460
Lipolysis in Brown Adipose Tissue 461
Objectives 462
Chapter 71: Ketone Body Formation and Utilization 463
Overview 463
Why Should one Lipid Fuel be Converted to Another in the Liver? 466
Ketone Body Utilization 467
Objectives 469
Chapter 72: Fatty Liver Syndrome (Steatosis) 471
Overview 471
Objectives 475
Addendum to Section V 476
Introduction to Section VI 476
Section VI: Starvation & Exercise
Chapter 73: Starvation (Transition into the Postabsorptive Phase) 478
Overview 478
The Insulin:Glucagon Ratio 479
Glucose Availability 481
The Initial Postabsorptive Phase of Starvation 481
Objectives 483
Chapter 74: Starvation (The Early Phase) 484
Overview 484
The Gluconeogenic Phase of Starvation 485
Objectives 488
Chapter 75: Starvation (The Intermediate Phase) 489
Overview 489
Objectives 493
Chapter 76: Starvation (The Late Phase) 495
Overview 495
Sequence of Body Protein Depletion 495
Starvation and Death 498
Starvation vs. Cachexia 498
The Survivors 498
Objectives 499
Chapter 77: Exercise (Circulatory Adjustments and Creatine) 500
Overview 500
Circulatory Adjustments to Exercise 501
Cardiac Adjustments to Exercise 501
Creatinine and Creatine 503
Objectives 505
Chapter 78: Exercise (VO2(max) and RQ) 506
Overview 506
Oxygen Consumption 506
The Respiratory Quotient (RQ) 508
Alternative Techniques for Determining Fuel Utilization During Exercise 509
Objectives 510
Chapter 79: Exercise (Substrate Utilization and Endocrine Parameters) 511
Overview 511
Objectives 515
Chapter 80: Exercise (Muscle Fiber Types and Characteristics) 516
Overview 516
Skeletal Muscle Fiber Types 516
Muscles That Do Not Accumulate an O2 Debt 519
Muscle Atrophy during Immobilization 520
Objectives 521
Chapter 81: Exercise (Athletic Animals) 522
Overview 522
Muscle Fatigue 522
Athletic Animals 523
Benefits of Conditioning 525
Objectives 526
Sections V and VI Examination Questions 527
Addendum to Section VI 545
Introduction to Section VII 545
Section VII: Acid-Base Balance 546
Chapter 82: The Hydrogen Ion Concentration 547
Overview 547
Hydrogen Ion Balance 548
Non-volatile Acid Production 549
Non-volatile Acid Input and Loss from the Body 550
Objectives 551
Chapter 83: Strong and Weak Electrolytes 552
Overview 552
The Henderson-Hasselbalch Equation 554
Objectives 556
Chapter 84: Protein Buffer Systems 557
Overview 557
The Hemoglobin (Hb–) Buffer System 558
Objectives 561
Chapter 85: Bicarbonate, Phosphate, and Ammonia Buffer Systems 562
Overview 562
The Bicarbonate Buffer System 562
The Phosphate Buffer System 564
The Ammonia Buffer System 566
Objectives 566
Chapter 86: Anion Gap 568
Overview 568
Plasma Anion Gap (AG) 568
Urinary Anion Gap (UAG) 570
Objectives 572
Chapter 87: Metabolic Acidosis 574
Overview 574
Effects of Chronic Acidemia on Bone 579
Objectives 579
Chapter 88: Diabetes Mellitus (Metabolic Acidosis and Potassium Balance) 581
Overview 581
Metabolic Acidosis and K+ Balance 582
Endocrine Influences on K+ Balance 585
Objectives 588
Chapter 89: Metabolic Alkalosis 589
Overview 589
Metabolic Alkalosis and K+ Balance 592
Volume-Resistant Metabolic Alkalosis 594
Objectives 595
Chapter 90: Respiratory Acidosis 597
Overview 597
Medullary Chemoreceptors 600
Objectives 602
Chapter 91: Respiratory Alkalosis 603
Overview 603
Mixed Acid-base Disturbances 606
Objectives 608
Chapter 92: Strong Ion Difference (SID) 609
Overview 609
Plasma Proteins and Phosphates 610
Free Water Abnormalities 610
Base Excess (BE) and Base Deficit (-BE) 611
Example Problem 611
Objectives 615
Chapter 93: Alkalinizing and Acidifying Solutions 619
Overview 619
Alkalinizing Solutions 619
Acidifying Solutions 622
Objectives 624
Chapter 94: Dehydration/Overhydration 625
Overview 625
Hypertonic Dehydration 625
Isotonic Dehydration 626
Hypotonic Dehydration 627
Indicators of Hypovolemia 628
Overhydration 628
Expansion of the ECF Volume 629
Objectives 630
Section VII Examination Questions 631
Epilog 639
Case Studies 640
Case Study #1: Ethylene Glycol 641
Questions 641
Answers 641
Case Study #2: Phosphofructokinase (PFK) 645
Questions 645
Answers 646
Case Study #3: Inflammatory Bowel Disease (IBD), Endocarditis and Cardiac Ischemia 648
Questions 648
Answers 649
Case Study #4: Portosystemic Vascular Shunt (PSS) 653
Questions 653
Answers 653
Case Study #5: Diabetes Mellitus (DM) 657
Questions 657
Answers 658
Case Study #6: Feline Lower Urinary Tract Disease(FLUTD) 662
Questions 662
Answers 662
Appendix 666
Abbreviations 674
References 688
Index 696

Textauszug

Chapter 1

Chemical Composition of Living Cells

Abstract

Most all diseases in animals are manifestations of abnormalities in biomolecules, chemical reactions, or biochemical pathways, so understanding the macromolecules within cells is critical. Hydrogen, oxygen, nitrogen, carbon, sulfur and phosphorus normally make up more than 99% of the mass of living cells. This chapter aims to give an overview of critical macromolecules, while going into more detail for the general structure and important details about intra and extracellular proteins; homogenous from heterogenous polymers; compound, simple and derived lipids. It also aims to allow readers to articulate how and why the inorganic elements are essential to life, as well as understand a basic understanding of physiological chemistry is fundamental to a clinical understanding of disease processes.

Keywords

Lipids

Polysaccharides

Proteins

Nucleic Acids

Macromolecules

biochemical pathways

biomolecules

OBJECTIVES

• Identify six elements that normally comprise over 99% of the living cell mass.

• Summarize the approximate chemical composition of a living cell.

• Give examples of functionally important intra- and extracellular proteins.

• Distinguish homogenous from heterogenous polymers, and give some examples.

• Understand basic differences between compound, simple and derived lipids.

• Indicate how and why the inorganic elements are essential to life.

• Recognize why a basic understanding of physiological chemistry is fundamental to a clinical understanding of disease processes.

Overview

• Hydrogen, oxygen, nitrogen, carbon, sulfur and phosphorus normally make up more than 99% of the mass of living cells.

• Ninety-nine percent of the molecules inside living cells are water molecules.

• Cells normally contain more protein than DNA.

• Homogenous polymers are noninformational.

• All non-essential lipids can be generated from acetyl-CoA.

• Like certain amino acids and unsaturated fatty acids, various inorganic elements are dietarily “essential.”

• Most all diseases in animals are manifestations of abnormalities in biomolecules, chemical reactions, or biochemical pathways.

All living organisms, from microbes to mammals, are composed of chemical substances from both the inorganic and organic world, that appear in roughly the same proportions, and perform the same general tasks. Hydrogen, oxygen, nitrogen, carbon, phosphorus, and sulfur normally make up more than 99% of the mass of living cells, and when combined in various ways, form virtually all known organic biomolecules. They are initially utilized in the synthesis of a small number of building blocks that are, in turn, used in the construction of a vast array of vital macromolecules (Fig 1-1).

Figure 1-1

There are four general classes of macromolecules within living cells: nucleic acids, proteins, polysaccharides, and lipids. These compounds, which have molecular weights ranging from 1 × 103 to 1 × 106, are created through polymerization of building blocks that have molecular weights in the range of 50 to 150. Although subtle differences do exist between cells (e.g., erythrocyte, liver, muscle or fat cell), they all generally contain a greater variety of proteins than any other type of macromolecule, with about 50% of the solid matter of the cell being protein (15% on a wet-weight basis). Cells generally contain many more protein molecules than DNA molecules, yet DNA is typically the largest biomolecule in the cell. About 99% of cellular molecules are water molecules, with water normally accounting for approximately 70% of the total wet-weight of the cell. Although water is obviously important to the vitality of all living cells, the bulk of our attention is usually focused on the other 1% of biomolecules.

Data in Table 1-1 regarding the chemical composition of the unicellular Escherichia coli (E. coli) are not greatly different for multicellular organisms, including mammals. Each E. coli, and similar bacterium, contains a single chromosome; therefore, it has only one unique DNA molecule. Mammals, however, contain more chromosomes, and thus have different DNA molecules in their nuclei.

Table 1-1

Approximate Chemical Composition of a Rapidly Dividing Cell (E. coli)

Water

70

1

Nucleic acids

DNA

1

1

RNA

6

Ribosomal

3

Transfer

40

Messenger

1000

Nucleotides and metabolites

0.8

200

Proteins

15

2000-3000

Amino acids and metabolites

0.8

100

Polysaccharides

3

200

(Carbohydrates and metabolites)

Lipids and metabolites

2

50

Inorganic ions

1

20

(Major minerals and trace elements)

Others

0.4

200

100

Data from Watson JD: Molecular Biology of the Gene, 2nd ed., Philadelphia, PA: Saunders, 1972

Nucleic Acids

Nucleic acids are nucleotide polymers (from the Greek word poly, meaning “several,” and mer, meaning “unit”), that store and transmit genetic information. Only 4 different nucleotides are used in nucleic acid biosynthesis. Genetic information contained in nucleic acids is stored and replicated in chromosomes, which contain genes (from the Greek word gennan, meaning “to produce”). A chromosome is a deoxyribonucleic acid (DNA) molecule, and genes are segments of intact DNA. The total number of genes in any given mammalian cell may total several thousand. When a cell replicates itself, identical copies of DNA molecules are produced; therefore the hereditary line of descent is conserved, and the genetic information carried on DNA is available to direct the occurrence of virtually all chemical reactions within the cell. The bulk of genetic information carried on DNA provides instructions for the assembly of every protein molecule within the cell. The flow of information from nucleic acids to protein is commonly represented as DNA → messenger ribonucleic acid (mRNA) → transfer RNA (tRNA) → ribosomal RNA (rRNA) → protein, which indicates that the nucleotide sequence in a gene of DNA specifies the assembly of a nucleotide sequence in an mRNA molecule, which in turn directs the assembly of the amino acid sequence in protein through tRNA and rRNA molecules.

Proteins

Proteins are amino acid polymers responsible for implementing instructions contained within the genetic code. Twenty different amino acids are used to synthesize proteins, about half are formed as metabolic intermediates, while the remainder must be provided through the diet. The latter group is referred to as “essential” amino acids (see Chapter 3). Each protein formed in the body, unique in its own structure and function, participates in processes that characterize the individuality of cells, tissues, organs, and organ systems. A typical cell contains thousands of different proteins, each with a different function, and many serve as enzymes that catalyze (or speed) reactions. Virtually every reaction in a living cell requires an enzyme. Other proteins transport different compounds either outside or inside cells {e.g., lipoproteins and transferrin (an iron-binding protein) in plasma, or bilirubin-binding proteins in liver cells}; some act as storage proteins (e.g., myoglobin binds and stores O2 in muscle cells); others as defense proteins in blood or on the surface of cells (e.g., clotting proteins and immunoglobulins); others as contractile proteins (e.g., the actin, myosin and troponin of skeletal muscle fibers); and others are merely structural in nature (e.g., collagen and elastin). Proteins, unlike glycogen and triglyceride, are usually not synthesized and stored as nonfunctional entities.

Polysaccharides

Polysaccharides are polymers of simple...

Produkt-Details

• Erscheint lt. Verlag: 12.8.2014
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie
• Themenwelt: Naturwissenschaften ► Biologie
• Themenwelt: Technik
• Themenwelt: Veterinärmedizin ► Vorklinik ► Physiologie
• Themenwelt: Weitere Fachgebiete ► Land- / Forstwirtschaft / Fischerei
• ISBN-10: 0-12-391910-X / 012391910X
• ISBN-13: 978-0-12-391910-6 / 9780123919106