Oxygen and the Evolution of Life (eBook)

Oxygen and the Evolution of Life 3
Preface 5
Contents 7
Abbreviations 11
Chapter 1: Oxygen, Its Nature and Chemistry: What Is so Special About This Element? 13
1.1 A Brief Introduction to Oxygen 13
1.2 Atomic Structure of Oxygen: Chemical Bonding Potential 14
1.3 The Dioxygen Molecule 17
1.4 Reactive Oxygen Species 20
1.4.1 Superoxide 1O2-* 20
1.4.2 Hydrogen peroxide (H2O2) 21
1.4.3 Peroxyl radical (ROO*) 21
1.5 Ozone 22
1.6 Water 24
1.7 Water Vapor in the Atmosphere 27
1.8 Carbon Dioxide 27
1.9 Solubility of Gases in Water 28
1.10 Hydrolysis and Dehydration: Central Water Reactions in Biology 28
1.11 Redox Reactions 29
References 30
Chapter 2: A Brief History of Oxygen 32
2.1 Cosmic History of the Elements 32
2.1.1 The Sun and Solar System 35
2.2 Formation of Earth 36
2.3 The Primordial Environment 38
2.3.1 Atmosphere of the Early Earth 38
2.3.2 Water on the Earth´ Surface: The Origin of Oceans 40
2.3.3 The First Greenhouse Effect 40
2.4 Life: Its Origins and Earliest Development 41
2.5 A Billion Years of Life Without Dioxygen: Anaerobic Metabolism 43
2.5.1 Some Principles of Metabolism 43
2.6 The Invention of Photosynthesis 46
2.7 How Oxygenic Photosynthesis Remodeled the Earth 49
2.7.1 The First Rise of Dioxygen 49
2.7.2 Effects on Life: An Ecological Catastrophe? 50
2.7.3 Effects on the Earth 51
References 52
Chapter 3: Coping with Oxygen 54
3.1 The Impact of Oxygenation on an Anaerobic World 54
3.2 Production of Reactive Oxygen Species 55
3.3 Coping with Reactive Oxygen Species 58
3.3.1 Scavenger Molecules 58
3.3.2 Enzymes for Detoxification of ROS 60
3.3.3 Antioxidant Enzyme Systems 62
3.4 How to Avoid Reactive Oxygen Species? 63
3.5 Evolving Defense Strategies 64
3.5.1 Aggregation for Defense 64
3.5.2 Melanin 65
3.5.3 Oxygen Transport Proteins Prevent Creation of Oxygen Radicals 66
3.6 Reactive Oxygen Species as Cellular Signals 67
3.7 Dioxygen as a Signal: Oxygen Sensor 67
3.8 Summary: Reactive Oxygen Species and Life 68
References 69
Chapter 4: Aerobic Metabolism: Benefits from an Oxygenated World 71
4.1 The Advantage to Being Aerobic 71
4.2 Evolution of an Aerobic Metabolism 72
4.2.1 Special Mechanisms Needed for Aerobic Metabolism 72
4.2.2 When and How Did Aerobes Arise? 73
4.3 Eukaryotes: The Next Step in Evolution 77
4.3.1 Distinction Between Prokaryotes and Eukaryotes 77
4.3.2 The Symbiotic Hypothesis 77
4.4 The Last Great Leap: Multicellular Organisms, ``Metazoans´´ 79
4.4.1 When, Why, and How? 79
4.4.2 Collagen and Cholesterin 80
4.4.3 Half a Billion Years of Stasis? 81
4.4.4 Emergence and Extinction of the Ediacaran Fauna 82
4.4.5 The Bilateral Body Plan 83
4.4.6 The ``Cambrian Explosion´´: Fact or Artifact? 84
References 86
Chapter 5: Facilitated Oxygen Transport 88
5.1 How to Deliver Dioxygen to Animal Tissues? 88
5.2 Modes of Delivery 89
5.2.1 Diffusion from the Surface 89
5.2.2 Transport via Blood as a Dissolved Gas 90
5.2.3 Oxygen Transport Proteins: What They Must Do? 91
5.3 Modes of Dioxygen Binding to Oxygen Transport Proteins 93
5.3.1 Cooperative and Noncooperative Binding 93
5.3.2 How Does Cooperativity Work?: Models for Allostery 95
5.3.3 Self-Assembly and Nesting 97
5.3.4 Why Complex Multisubunit Oxygen Transport Proteins? 98
5.4 Modulation of Dioxygen Delivery by Oxygen Transport Proteins: Heteroallostery 98
5.4.1 Modulation by the Products of Anaerobic Metabolism: the Bohr Effect 99
5.4.2 The Haldane Effect 99
5.4.3 The Root Effect 100
5.4.4 Temperature Dependence 101
5.4.5 Evolutionary Aspects of Regulation 102
5.5 Diversity of Oxygen Transport Proteins 102
5.5.1 Hemoglobins 103
5.5.2 Hemerythrins 105
5.5.3 Hemocyanins 105
5.5.3.1 Molluscan Hemocyanin 106
5.5.3.2 Arthropod Hemocyanins 107
5.6 Evolution of Oxygen Transport Proteins 108
5.7 Was Snowball Earth a Possible Trigger for OPT Evolution? 110
5.8 From What Proteins Did Oxygen Transport Proteins Evolve? 111
5.9 Oxygen Transport Proteins and ``Intelligent Design´´ 112
References 112
Chapter 6: Climate Over the Ages Is the Environment Stable?
6.1 Climate and Glaciations in Earth´s History 116
6.1.1 The First Massive Glaciations the Huronion Event: A Role for Methane?
6.1.2 Later Proterozoic Glaciations 118
6.1.3 Phanerozoic Climate and Glaciations 119
6.2 How Did Life Survive Glaciations? 124
6.3 Milestones of Life in the Phanerozoic 126
6.4 Inorganic Cycling of Carbon Dioxide 129
6.5 Is Our Environment Stable? 130
6.6 Recent Global Warming 132
References 132
Chapter 7: Global Warming: Human Intervention in World Climate 135
7.1 Recent Climate Changes 135
7.2 Physical Consequences of Global Warming 137
7.2.1 Shrinking Ice and Glaciers 137
7.2.2 Sea Level Changes 138
7.2.3 Changes in Ocean Currents 139
7.2.4 Local Climate and Weather 140
7.2.5 The Danger of Methane Releases 141
7.2.6 Greenhouse to Icehouse and Vice Versa? 141
7.3 Human Consequences of Global Warming 142
7.3.1 Direct Consequences of CO2 and Temperature Increase 142
7.3.2 Sea Level Rise 143
7.3.3 Extreme Weather 144
7.3.4 Effects on Agriculture 145
7.4 Control of Global Warming 146
7.4.1 Positive and Negative Natural Feedback Mechanism 146
7.4.2 Human Efforts to Control Global Warming 147
7.4.3 The Long View 147
References 148
Chapter 8: Oxygen in Medicine 150
8.1 Hypoxia 150
8.1.1 High-Altitude Hypoxia 151
8.1.2 Hypoxia Arising from Medical Conditions 152
8.2 Oxidative Stress 152
8.2.1 Nature of Oxidative Stress 152
8.2.2 Special Examples of Medical Consequences of Oxidative Stress 153
8.2.2.1 DNA 154
8.2.2.2 Proteins 154
8.3 Treatment of Oxidative Stress 156
8.4 Beneficial Roles of ROS 157
8.4.1 SCN and Primary Immune Response 157
8.4.2 Nitric Oxide 158
References 160
Chapter 9: Oxygen and the Exploration of the Universe 163
9.1 What Is Essential for the Development of Life as We Know It? 163
9.2 What Makes O2 Necessary for Complex Life on Habitable Planets? 164
9.3 Seeking Evidence for Extraterrestrial Life 164
9.4 Life in the Solar System? 167
9.4.1 Terrestrial Planets 167
9.4.1.1 Venus 168
9.4.1.2 Mars 169
9.4.2 Icy Moons 169
9.5 Oxygen Supply Problems in Extraterrestrial Voyages 170
9.6 Problems Facing Extended Extraterrestrial Settlement or Colonization 172
9.6.1 Adjusting the Planetary Environment: Terraforming 172
9.6.2 Adjusting the Organism: Bioforming 173
References 174
Index 175