Textbook of Veterinary Physiological Chemistry, Updated 2/e (eBook)

Larry R. Engelking (Autor)

eBook Download: PDF | EPUB

2010 | 2. Auflage
608 Seiten
Elsevier textbooks (Verlag)
978-0-12-384853-6 (ISBN)

Infos

Written in a succinct style with each chapter including an overview summary section, numerous illustrations for best comprehension, and end of the chapter questions to assess understanding, The Textbook of Veterinary Physiological Chemistry offers broad coverage of biochemical principles for students studying veterinary medicine. Since first year students come into programs with different scientific backgrounds, this text offers students foundational concepts in physiological chemistry and offers numerous opportunities for practice. Bridging the gap between science and clinical application of concepts, this textbook covers cellular level concepts related to the biochemical processes in the entire animal in a student-friendly, approachable manner.

Inhalt

Front Cover 
1 
Textbook of Veterinary Physiological Chemistry 2
Copyright Page 
3 
Table of Contents 4
About the Author 7
Acknowledgments 8
Preface to the First Edition 10
Preface to the Second Edition 11
Section I: Amino Acid and Protein Metabolism 12
Chaper 1: Chemical Composition of Living Cells 13
Nucleic Acids 14
Proteins 15
Polysaccharides 16
Lipids 16
Objectives 17
Questions 
17 
Chapter 2: Properties of Amino Acids 18
Hydrophilic Amino Acids 20
Hydrophobic Amino Acids 20
Neither Hydrophobic nor Hydrophilic 21
Enantiomers 21
Objectives 
21 
Questions 
21 
Chapter 3: Amino Acid Modifications 23
Modified Amino Acids Found in Protein 23
Nonprotein Amino Acids 26
Essential and Nonessential Amino Acids 26
Objectives 
27 
Questions 
28 
Chapter 4: Protein Structure 
29 
Primary Structure 29
Secondary Structure 30
Tertiary Structure 32
Quaternary Structure 33
Prion Diseases 33
Protein Denaturation 33
Objectives 
33 
Questions 
34 
Chapter 5: Properties of Enzymes 35
General Properties of Enzymes 36
Enzyme Nomenclature 36
Coenzymes 36
Control of Enzyme Activity 36
Objectives 
39 
Questions 
39 
Chapter 6: Enzyme Kinetics 41
Substrate Saturation Curves 41
Double Reciprocal Plots 42
Enzyme Inhibitors 43
Reversible, Competitive Inhibitors 43
Reversible, Noncompetitive Inhibitors 43
Uncompetitive Inhibitors 44
Irreversible Inhibitors 44
Therapeutic Inhibitors 44
Isozymes 44
Objectives 
45 
Questions 
46 
Chapter 7: Protein Digestion 47
Tissue Protein Turnover 47
Gastrointestinal Protein Digestion 48
Objectives 51
Questions 
52 
Chapter 8: Amino Acid Catabolism 53
Hepatic Metabolism of Phenylalanine 53
The BCAA/AAA Ratio 54
Intestine 56
Skeletal Muscle 56
Brain 56
Kidney 56
Liver 57
Nitrogen Balance 57
Objectives 
58 
Questions 59
Chapter 9: Transamination and Deamination Reactions 60
Deamination Reactions 
61 
Transamination Reactions 
63 
Other Transaminases 64
Objectives 65
Questions 65
Chapter 10: Urea Cycle (Krebs-Henseleit Ornithine Cycle) 66
Carbamoyl Phosphate Formation 67
Citrulline Formation 67
Argininosuccinate Formation 67
Arginine and Fumarate Formation 69
Disposal of Urea 69
Abnormalities in Urea Biosynthesis 70
Objectives 70
Questions 71
Chapter 11: Glutamine and Ammonia 72
Ammonia Toxicity 72
Nitrogen and Carbon Flux Between Liver and Kidney 
72 
Objectives 76
Questions 
76 
Chapter 12: Nonprotein Derivatives of Amino Acids 77
Tyrosine (Tyr) 77
Tryptophan (Trp) 78
Histidine (His) 78
Glutamate (Glu) 80
Glycine (Gly) 80
Arginine (Arg) 80
Lysine (Lys) 81
Serine (Ser) 81
Objectives 81
Questions 82
Addendum to Section I 83
Introduction to Section II 83
Section II: Nucleotide and Nucleic Acid Metabolism 84
Chapter 13: Nucleotides 85
Nucleotide Structure 86
Polynucleotide Structure and Synthesis 88
Objectives 89
Questions 89
Chapter 14: Pyrimidine Biosynthesis 
90 
Pathway Summary 90
Pathway Regulation 92
Unusual Physical Properties of Relevant Early Stage Mammalian Enzymes 92
Objectives 
94 
Questions 94
Chapter 15: Purine Biosynthesis 95
Phase One - PRPP Biosynthesis 97
Phase Two - Formation of IMP (the parent NMP) 97
Phase Three - Formation of AMP, GMP, and the Respective 5'- 
97 
Formation of NDP and NTP Forms of Adenine and Guanine 98
Regulation of Purine Biosynthesis 98
Objectives 99
Questions 99
Chapter 16: Folic Acid 
100 
Folic Acid and its Active Form, Tetrahydrofolate 
100 
Folate Metabolism in Animals vs 
100 
THFA-mediated One-carbon Metabolism 102
Megaloblastic Anemia (MA) 102
Formation of Deoxyribonucleotides 103
Conversion of dUTP to its 5-methyl Form, dTTP 103
Chemotherapeutic Drug Targets in dNTP and Folate Metabolism 103
Objectives 104
Questions 104
Chapter 17: Nucleic Acid and Nucleotide Turnover 105
Release of Bases from Nucleic Acids 105
Nucleotides and Nucleosides 106
Salvage of Purine and Pyrimidine Bases 106
Degradation of Pyrimidine Bases 107
Degradation of Purine Bases 108
Excretion of Purine Degradation Products 110
Uric Acid and Health 110
Objectives 111
Questions 111
Section III: Carbohydrate and Heme Metabolism 112
Chapter 18: Carbohydrate Structure 
113 
Complex Carbohydrates 113
Monosaccharides 114
Pentoses, NAD+ and NADP+, NADH and NADPH 114
Disaccharides and Trisaccharides 116
Objectives 117
Questions 117
Chapter 19: Polysaccharides and Carbohydrate Derivatives 119
Polysaccharides 119
Carbohydrate Derivatives 121
Objectives 124
Questions 124
Chapter 20: Glycoproteins and Glycolipids 125
Glycoproteins 125
Glycolipids 129
Objectives 130
Questions 130
Chapter 21: Overview of Carbohydrate Metabolism 131
Objectives 135
Questions 135
Chapter 22: Glucose Trapping 136
Objectives 140
Questions 141
Chapter 23: Glycogen 142
Glycogenesis 143
Glycogenolysis 144
Glycogen Storage Diseases 146
Objectives 147
Questions 147
Chaper 24: Introduction to Glycolysis (The Embden-Meyerhoff Pathway (EMP)) 148
Objectives 152
Questions 152
Chapter 25: Initial Reactions in Anaerobic Glycolysis 153
Objectives 157
Questions 157
Chapter 26: Intermediate Reactions in Anaerobic Glycolysis 158
Objectives 162
Questions 162
Chapter 27: Metabolic Fates of Pyruvate 163
Objectives 166
Questions 167
Chapter 28: Hexose Monophosphate Shunt (HMS) 168
Objectives 171
Questions 172
Chapter 29: Uronic Acid Pathway 173
Objectives 177
Questions 177
Chapter 30: Erythrocytic Protection from O2 Toxicity 178
Oxygen Toxicity 178
Cellular Protection Against Free Radicals 179
Objectives 182
Questions 182
Chapter 31: Carbohydrate Metabolism in Erythrocytes 183
Objectives 186
Questions 187
Chapter 32: Heme Biosynthesis 188
Hemoglobin (Hb) 191
Anemias and Polycythemia 192
Objectives 193
Questions 193
Chapter 33: Heme Degradation 194
Hepatic Bilirubin Uptake, Conjugation, and Excretion 
196 
Characterization of Plasma Bilirubin 197
Objectives 199
Questions 199
Chapter 34: Tricarboxylic Acid (TCA) Cycle 200
Objectives 204
Questions 204
Chapter 35: Leaks in the Tricarboxylic Acid (TCA) Cycle 205
TCA Cycle Intermediates are Converted to Other Essential Compounds 205
Replenishment of TCA Cycle Intermediates 207
Objectives 209
Questions 209
Chapter 36: Oxidative Phosphorylation 210
Movement of Electrons from Cytoplasmic NADH to the Mitochondrial ETC 210
Oxidation and Reduction 213
Phosphorylation 213
Inhibitors and Uncouplers 214
Objectives 214
Questions 215
Chapter 37: Gluconeogenesis 216
Gluconeogenic Precursors 218
Gluconeogenic Enzymes 219
Objectives 221
Questions 221
Chapter 38: Carbohydrate Digestion 222
Salivary a-Amylase (Ptyalin) 
222 
Intestinal Carbohydrate Digestion 223
Luminal Phase (Pancreatic a-Amylase) 
223 
Brush Border Phase (Oligosaccharidases) 224
Intestinal Monosaccharide Absorption 225
Objectives 227
Questions 228
Section IV: Vitamins and Trace Elements 230
Chapter 39: Vitamin C 231
Water-soluble Vitamins 231
Objectives 236
Questions 236
Chapter 40: Thiamin (B1) and Riboflavin (B2) 237
Thiamin (Vitamin B1) 237
Riboflavin (Vitamin B2) 239
Objectives 241
Questions 241
Chapter 41: Niacin (B3) and Pantothenic Acid (B5) 242
Niacin (Vitamin B3) 242
Pantothenic Acid (Vitamin B5) 244
Lipoic acid 246
Objectives 246
Questions 246
Chapter 42: Biotin and Pyridoxine (B6) 248
Biotin 248
Pyridoxine (B6) 251
Objectives 252
Questions 252
Chapter 43: Cobalamin (B12) 253
Objectives 257
Questions 257
Chapter 44: Vitamin A 259
Fat-Soluble Vitamins 259
Vitamin A 259
Vitamin A Toxicity 261
Vitamin A and Vision 262
Vitamin A Deficiency 262
Objectives 264
Questions 264
Chapter 45: Vitamin D 265
Vitamin D Toxicity 269
Vitamin D Deficiency 269
Objectives 270
Questions 270
Chapter 46: Vitamin E 271
Vitamin E Deficiency 274
Objectives 275
Questions 275
Chapter 47: Vitamin K 276
Vitamin K Deficiency 278
Vitamin K Toxicity 280
Objectives 280
Questions 280
Chapter 48: Iron 281
Trace Elements 281
Iron (Fe) 281
Iron Toxicity 284
Iron Deficiency 284
Objectives 285
Questions 285
Chapter 49: Zinc 286
Zinc Toxicity 289
Objectives 290
Questions 290
Chapter 50: Copper 291
Copper Deficiency 294
Copper Toxicity 294
Objectives 295
Questions 295
Chapter 51: Manganese and Selenium 296
Manganese (Mn++) 296
Selenium (Se) 298
Objectives 301
Questions 301
Chapter 52: Iodine and Cobalt 302
Cobalt (Co) 304
Objectives 306
Questions 306
Addendum to Section IV 307
Introduction to Section V 307
Section V: Lipid Metabolism 308
Chapter 53: Overview of Lipid Metabolism 309
Objectives 313
Questions 313
Chapter 54: Saturated and Unsaturated Fatty Acids 314
Essential Fatty Acids 316
Objectives 319
Questions 
319 
Chapter 55: Fatty Acid Oxidation 320
Mitochondrial ß-oxidation 
322 
Peroxisomal ß-oxidation 
323 
Objectives 325
Questions 325
Chapter 56: Fatty Acid Biosynthesis 326
Fatty Acid Elongation Beyond Palmitate 328
NADPH Generation and FattyAcid Biosynthesis 328
Objectives 
331 
Questions 331
Chapter 57: Triglycerides and Glycerophospholipids 332
Triglycerides 332
Glycerophospholipids 334
Objectives 337
Questions 337
Chapter 58: Phospholipid Degradation 338
Phospholipids and the Ca++ Messenger System 339
Tumor Promoters and PKC 341
Objectives 342
Questions 342
Chapter 59: Sphingolipids 343
Sphingolipid Degradation 347
Objectives 348
Questions 348
Chapter 60: Lipid Digestion 349
Emulsification of Dietary Fat 350
Enzymatic Hydrolysis of Dietary Lipids 350
Lipid Absorption in the Small Intestine 351
Mucosal Resynthesis of Dietary Lipids 351
Abnormalities in Lipid Digestion and Absorption 352
Objectives 354
Questions 354
Chapter 61: Cholesterol 355
Cholesterol Biosynthesis 357
Abnormalities in the Plasma Cholesterol Concentration 359
Objectives 360
Questions 360
Chapter 62: Bile Acids 361
Hepatic BA Biosynthesis 361
Bile Acid Actions in Bile, and in Luminal Contents of the Intestine 364
Intestinal Bile Acid Reabsorption and Enterohepatic Cycling 365
Objectives 366
Questions 366
Chapter 63: Lipoprotein Complexes 367
Apoproteins 368
FFA-Albumin Complexes 369
Objectives 371
Questions 371
Chapter 64: Chylomicrons 372
Objectives 376
Questions 376
Chapter 65: VLDL, IDL, and LDL 377
Very Low-Density Lipoprotein (VLDL) 377
Intermediate-Density (IDL), and Low-Density Lipoprotein (LDL) 379
Objectives 381
Questions 381
Chapter 66: LDL Receptors and HDL 382
Nature of the Low-Density Lipoprotein(LDL) Receptor 382
High-Density Lipoprotein (HDL) 384
Objectives 386
Questions 387
Chapter 67: Hyperlipidemias 388
Objectives 393
Questions 393
Chapter 68: Eicosanoids I 394
Eicosanoid Degradation and Activity 396
Thromboxanes 397
Objectives 398
Questions 398
Chapter 69: Eicosanoids II 399
Hydroperoxyeicosatetraenoic Acids (HPETEs) and Hydroxyeicosatetraenoic Acids (HETEs) 399
Leukotrienes (LTs) 399
Prostaglandins (PGs) 401
Objectives 403
Questions 403
Chapter 70: Lipolysis 404
Endocrine Control of Lipolysis 405
Glyceroneogenesis 407
Satiety 407
Lipolysis in Brown Adipose Tissue 408
Objectives 409
Questions 409
Chapter 71: Ketone Body Formation and Utilization 410
Why Should one Lipid Fuel be Converted to Another in the Liver? 413
Ketone Body Utilization 414
Objectives 415
Questions 415
Chapter 72: Fatty Liver Syndrome (Steatosis) 416
Other Symptoms of Steatosis 419
Objectives 420
Questions 420
Addendum to Section V 421
Introduction to Section VI 421
Section VI: Intermediary Metabolism 422
Chapter 73: Starvation (Transition into the Postabsorptive Phase) 423
The Insulin: 
424 
Glucose Availability 426
The Initial Postabsorptive Phase of Starvation 426
Objectives 428
Questions 428
Chapter 74: Starvation (The Early Phase) 429
The Gluconeogenic Phase of Starvation 430
Objectives 433
Questions 433
Chapter 75: Starvation (The Intermediate Phase) 434
Objectives 437
Questions 438
Chapter 76: Starvation (The Late Phase) 439
Sequence of Body Protein Depletion 439
Starvation and Death 442
Starvation vs. Cachexia 442
The Survivors 442
Objectives 443
Questions 443
Chapter 77: Exercise (Circulatory Adjustments and Creatine) 444
Circulatory Adjustments to Exercise 445
Cardiac Adjustments to Exercise 445
Creatinine and Creatine 447
Objectives 449
Questions 449
Chapter 78: Exercise (VO2(max) and RQ) 450
Oxygen Consumption 450
The Respiratory Quotient (RQ) 452
Alternative Techniques for Determining Fuel Utilization During Exercise 453
Objectives 454
Questions 454
Chapter-79: Exercise (Substrate Utilization and Endocrine Parameters) 455
Objectives 
459 
Questions 
459 
Chapter 80: Exercise (Muscle Fiber Types and Characteristics) 460
Skeletal Muscle Fiber Types 460
Muscles That Do Not Accumulate an O2 Debt 463
Muscle Atrophy during Immobilization 464
Objectives 465
Questions 465
Chapter 81: Exercise (Athletic Animals) 466
Muscle Fatigue 466
Athletic Animals 467
Benefits of Conditioning 469
Objectives 470
Questions 470
Addendum to Section VI 471
Introduction to Section VII 471
Section VII: Acid-Base Balance 472
Chapter 82: The Hydrogen Ion Concentration 473
Hydrogen Ion Balance 474
Non-volatile Acid Production 475
Non-volatile Acid Input and Loss from the Body 476
Objectives 477
Questions 477
Chapter 83: Strong and Weak Electrolytes 478
The Henderson-Hasselbalch Equation 480
Objectives 482
Questions 482
Chapter 84: Protein Buffer Systems 483
The Hemoglobin (Hb–) Buffer System 484
Objectives 487
Questions 487
Chapter 85: Bicarbonate, Phosphate, and Ammonia Buffer Systems 488
The Bicarbonate Buffer System 488
The Phosphate Buffer System 490
The Ammonia Buffer System 491
Objectives 492
Questions 492
Chapter 86: Anion Gap 494
Plasma Anion Gap (AG) 494
Urinary Anion Gap (UAG) 496
Objectives 499
Questions 499
Chapter 87: Metabolic Acidosis 500
Effects of Chronic Acidemia on Bone 505
Objectives 505
Questions 505
Chapter 88: Diabetes Mellitus (Metabolic Acidosis and 
507 
Metabolic Acidosis and K+ Balance 508
Endocrine Influences on K+ Balance 511
Objectives 513
Questions 513
Chapter 89: Metabolic Alkalosis 514
Metabolic Alkalosis and K+ Balance 517
Volume-Resistant Metabolic Alkalosis 519
Objectives 520
Questions 520
Chapter 90: Respiratory Acidosis 521
Medullary Chemoreceptors 524
Objectives 526
Questions 526
Chapter 91: Respiratory Alkalosis 527
Mixed Acid-base Disturbances 530
Objectives 532
Questions 532
Chapter 92: Strong Ion Difference (SID) 533
Plasma Proteins and Phosphates 534
Free Water Abnormalities 534
Base Excess (BE) and Base Deficit (-BE) 535
Objectives 539
Questions with Explanations 539
Chapter 93: Alkalinizing and Acidifying Solutions 543
Alkalinizing Solutions 543
Acidifying Solutions 546
Objectives 548
Questions 548
Chapter 94: Dehydration/Overhydration 549
Hypertonic Dehydration 549
Isotonic Dehydration 550
Hypotonic Dehydration 551
Indicators of Hypovolemia 552
Overhydration 552
Expansion of the ECF Volume 553
Objectives 554
Questions 554
Appendix 556
Abbreviations 564
References 578
Index 584

Textauszug

Chapter 1

Chemical Composition of Living Cells

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 intraand 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 makeup 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 mam-mals, 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)

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 bilirubinbinding 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 sugars (i.e., monosaccharides). (The term saccharide is derived from the Greek word sakchar, meaning “sugar or sweetness.”) Some polysaccharides are homogenous polymers that contain only one kind of sugar (e.g., glycogen), while others are complex heterogenous polymers that contain 8-10 types of sugar. In contrast to heterogenous polymers (e.g., proteins, nucleic acids, and some polysaccharides), homogenous polymers are considered to be “noninformational.” Polysaccharides, therefore, can occur as functional and structural components of cells (e.g., glycoproteins and glycolipids), or merely as noninformational storage forms of energy (e.g., glycogen). The 8- 10 monosaccharides that become the building blocks for heterogenous polysaccharides can be synthesized from glucose, or formed from other metabolic intermediates (see Chapter 20).

Lipids

Lipids (from the Greek word lipos, meaning “fat”) are naturally occurring, nonpolar substances that are mostly insoluble in water (with the exceptions being the short-chain volatile fatty acids and ketone bodies), yet soluble in nonpolar solvents (like chloroform and ether). They serve as membrane components (cholesterol, glycolipids and phospholipids), storage forms of energy (triglycerides), precursors to other important biomolecules (fatty acids), insulation barriers (neutral fat stores), protective coatings to prevent infection and excessive gain or loss of water, and some vitamins (A, D, E, and K) and hormones (steroid hormones). Major classes of lipids are the saturated and unsaturated fatty acids (short, medium, and long-chain), triglycerides, lipoproteins {i.e., chylomicrons (CMs), very low density (VLDL), low density (LDL), intermediate density (IDL), and high density lipoproteins (HDL)}, phospholipids and glycolipids, steroids (cholesterol, progesterone, etc.), and eicosanoids (prostaglandins, thromboxanes, and leukotrienes). All lipids can be synthesized from acetyl-CoA, which in turn can be generated from numerous different sources, including carbohydrates, amino acids, short-chain volatile fatty acids (e.g., acetate), ketone bodies, and fatty acids. Simple lipids include only those that are esters of fatty acids and an alcohol (e.g., mono-, di- and triglycerides). Compound lipids include various materials that contain other substances in addition to an alcohol and fatty acid (e.g.,...

Produkt-Details

• Erscheint lt. Verlag: 6.7.2010
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie
• Themenwelt: Naturwissenschaften ► Biologie
• Themenwelt: Naturwissenschaften ► Chemie
• Themenwelt: Technik
• Themenwelt: Veterinärmedizin ► Vorklinik ► Physiologie
• Themenwelt: Weitere Fachgebiete ► Land- / Forstwirtschaft / Fischerei
• ISBN-10: 0-12-384853-9 / 0123848539
• ISBN-13: 978-0-12-384853-6 / 9780123848536