indice I Introduction to the Cell The Evolution of the Cell Introduction From Molecules to the First Cell From Procaryotes to Eucaryotes From Single Cells to Multicellular Organisms References General Cited Small Molecules, Energy, and Biosynthesis Introduction The Chemical Components of a Cell Biological Order and Energy Food and the Derivation of Cellular Energy Biosynthesis and the Creation of Order The Coordination of Catabolism and Biosynthesis References General Cited Macromolecules: Structure, Shape, and Information Introduction Molecular Recognition Processes Nucleic Acids Protein Structure Proteins as Catalysts References General Cited How Cells Are Studied file:///H|/albert/paginas/indice.htm (1 of 7) [29/05/2003 04:53:06 a.m.] indice Introduction Looking at the Structure of Cells in the Microscope Isolating Cells and Growing Them in Culture Fractionation of Cells and Analysis of Their Molecules Tracing and Assaying Molecules Inside Cells References General Cited II Molecular Genetics Protein Function Introduction Making Machines Out of Proteins The Birth, Assembly, and Death of Proteins References General Cited Basic Genetic Mechanisms Introduction RNA and Protein Synthesis DNA Repair DNA Replication Genetic Recombination Viruses, Plasmids, and Transposable Genetic Elements References General Cited Recombinant DNA Technology Introduction The Fragmentation, Separation, and Sequencing of DNA Molecules Nucleic Acid Hybridization DNA Cloning DNA Engineering References Cited file:///H|/albert/paginas/indice.htm (2 of 7) [29/05/2003 04:53:06 a.m.] indice The Cell Nucleus Introduction Chromosomal DNA and Its Packaging The Global Structure of Chromosomes Chromosome Replication RNA Synthesis and RNA Processing The Organization and Evolution of the Nuclear Genome References Cited Control of Gene Expression Introduction An Overview of Gene Control DNA-binding Motifs in Gene Regulatory Proteins How Genetic Switches Work Chromatin Structure and the Control of Gene Expression The Molecular Genetic Mechanisms That Create Specialized Cell Types Posttranscriptional Controls References General Cited III Internal Organization of the Cell 10 Membrane Structure Introduction The Lipid Bilayer Membrane Proteins References General Cited 11 Membrane Transport of Small Molecules and the Ionic Basis of Membrane Excitability Introduction Principles of Membrane Transport Carrier Proteins and Active Membrane Transport , Ion Channels and Electrical Properties of Membranes References file:///H|/albert/paginas/indice.htm (3 of 7) [29/05/2003 04:53:06 a.m.] indice 12 Intracellular Compartments and Protein Sorting Introduction The Compartmentalization of Higher Cells The Transport of Molecules into and out of the Nucleus The Transport of Proteins into Mitochondria and Chloroplasts Peroxisomes The Endoplasmic Reticulum References General Cited 13 Vesicular Traffic in the Secretory and Endocytic Pathways Introduction Transport from the ER Through the Golgi Apparatus Transport from the Trans Golgi Network to Lysosomes Transport from the Plasma Membrane via Endosomes: Endocytosis Transport from the Trans Golgi Network to the Cell Surface: Exocytosis The Molecular Mechanisms of Vesicular Transport and the Maintenance of Compartmental Diversity References General Cited 14 Energy Conversion: Mitochondria and Chloroplasts Introduction The Mitochondrion The Respiratory Chain and ATP Synthase Chloroplasts and Photosynthesis The Evolution of Electron-Transport Chains The Genomes of Mitochondria and Chloroplasts References General Cited 15 Cell Signaling Introduction General Principles of Cell Signaling Signaling via G-Protein-linked Cell-Surface Receptors Signaling via Enzyme-linked Cell-Surface Receptors Target-Cell Adaptation The Logic of Intracellular Signaling: Lessons from Computer-based "Neural Networks" file:///H|/albert/paginas/indice.htm (4 of 7) [29/05/2003 04:53:06 a.m.] indice References General Cited 16 The Cytoskeleton Introduction The Nature of the Cytoskeleton Intermediate Filaments Microtubules Cilia and Centrioles Actin Filaments Actin-binding Proteins Muscle References General Cited 17 The Cell-Division Cycle Introduction The General Strategy of the Cell Cycle The Early Embryonic Cell Cycle and the Role of MPF Yeasts and the Molecular Genetics of Cell-Cycle Control Cell-Division Controls in Multicellular Animals References General Cited 18 The Mechanics of Cell Division Introduction An Overview of M Phase Mitosis Cytokinesis References General Cited IV Cells in Their Social Context 19 Cell Junctions, Cell Adhesion, and the Extracellular Matrix Introduction file:///H|/albert/paginas/indice.htm (5 of 7) [29/05/2003 04:53:06 a.m.] indice Cell Junctions Cell-Cell Adhesion The Extracellular Matrix of Animals Extracellular Matrix Receptors on Animal Cells: The Integrins The Plant Cell Wall References Cited 20 Germ Cells and Fertilization Introduction The Benefits of Sex Meiosis Eggs Sperm Fertilization References General Cited 21 Cellular Mechanisms of Development Introduction Morphogenetic Movements and the Shaping of the Body Plan Cell Diversification in the Early Animal Embryo , Cell Memory, Cell Determination, and the Concept of Positional Values The Nematode Worm: Developmental Control Genes and the Rules of Cell Behavior Drosophila and the Molecular Genetics of Pattern Formation I Genesis of the Body Plan Drosophila and the Molecular Genetics of Pattern Formation II Homeotic Selector Genes and the Patterning of Body Parts , Plant Development Neural Development References General Cited 22 Differentiated Cells and the Maintenance of Tissues Introduction Maintenance of the Differentiated State Tissues with Permanent Cells Renewal by Simple Duplication file:///H|/albert/paginas/indice.htm (6 of 7) [29/05/2003 04:53:06 a.m.] indice Renewal by Stem Cells: Epidermis , Renewal by Pluripotent Stem Cells: Blood Cell Formation , Genesis, Modulation, and Regeneration of Skeletal Muscle Fibroblasts and Their Transformations: The Connective-Tissue Cell Family Appendix References General Cited 23 The Immune System Introduction The Cellular Basis of Immunity The Functional Properties of Antibodies The Fine Structure of Antibodies The Generation of Antibody Diversity T Cell Receptors and Subclasses MHC Molecules and Antigen Presentation to T Cells Cytotoxic T Cells Helper T Cells and T Cell Activation Selection of the T Cell Repertoire References General Cited 24 Cancer Introduction Cancer as a Microevolutionary Process The Molecular Genetics of Cancer References General Cited file:///H|/albert/paginas/indice.htm (7 of 7) [29/05/2003 04:53:06 a.m.] From Procaryotes to Eucaryotes I: Introduction to the Cell The Evolution of the Cell Introduction From Molecules to the First Cell From Procaryotes to Eucaryotes From Single Cells to Multicellular Organisms References Introducción From Molecules to the First Cell Complex Chemical Systems Can Develop in an Environment That Is Far from Chemical Equilibrium Polynucleotides Are Capable of Directing Their Own Synthesis Self-replicating Molecules Undergo Natural Selection Specialized RNA Molecules Can Catalyze Biochemical Reactions Information Flows from Polynucleotides to Polypeptides Membranes Defined the First Cell All Present-Day Cells Use DNA as Their Hereditary Material Summary Referencias key terms file:///H|/albert/paginas/from_procaryotes_to_eucaryotes.htm (1 of 25) [29/05/2003 04:53:10 a.m.] From Procaryotes to Eucaryotes Introduction All living creatures are made of cells - small membrane-bounded compartments filled with a concentrated aqueous solution of chemicals The simplest forms of life are solitary cells that propagate by dividing in two Higher organisms, such as ourselves, are like cellular cities in which groups of cells perform specialized functions and are linked by intricate systems of communication Cells occupy a halfway point in the scale of biological complexity We study them to learn, on the one hand, how they are made from molecules and, on the other, how they cooperate to make an organism as complex as a human being All organisms, and all of the cells that constitute them, are believed to have descended from a common ancestor cell through evolution by natural selection This involves two essential processes: (1) the occurrence of random variation in the genetic information passed from an individual to its descendants and (2) selection in favor of genetic information that helps its possessors to survive and propagate Evolution is the central principle of biology, helping us to make sense of the bewildering variety in the living world This chapter, like the book as a whole, is concerned with the progression from molecules to multicellular organisms It discusses the evolution of the cell, first as a living unit constructed from smaller parts and then as a building block for larger structures Through evolution, we introduce the cell components and activities that are to be treated in detail, in broadly similar sequence, in the chapters that follow Beginning with the origins of the first cell on earth, we consider how the properties of certain types of large molecules allow hereditary information to be transmitted and expressed and permit evolution to occur Enclosed in a membrane, these molecules provide the essentials of a self-replicating cell Following this, we describe the major transition that occurred in the course of evolution, from small bacteriumlike cells to much larger and more complex cells such as are found in present-day plants and animals Lastly, we suggest ways in which single free-living cells might have given rise to large multicellular organisms, becoming specialized and cooperating in the formation of such intricate organs as the brain Clearly, there are dangers in introducing the cell through its evolution: the large gaps in our knowledge can be filled only by speculations that are liable to be wrong in many details We cannot go back in time to witness the unique molecular events that took place billions of years ago But those ancient events have left many traces for us to analyze Ancestral plants, animals, and even bacteria are preserved as fossils Even more important, every modern organism provides evidence of the character of living organisms in the past Present-day biological molecules, in particular, are a rich source of information about the course of evolution, revealing fundamental similarities between the most disparate of living organisms and allowing us to map out the differences between them on an objective universal scale These molecular similarities and differences present us with a problem like that which confronts the literary scholar who seeks to establish the original text of an ancient author by comparing a mass of variant file:///H|/albert/paginas/from_procaryotes_to_eucaryotes.htm (2 of 25) [29/05/2003 04:53:10 a.m.] From Procaryotes to Eucaryotes manuscripts that have been corrupted through repeated copying and editing The task is hard, and the evidence is incomplete, but it is possible at least to make intelligent guesses about the major stages in the evolution of living cells From Molecules to the First Cell1 Simple Biological Molecules Can Form Under Prebiotic Conditions1,2 The conditions that existed on the earth in its first billion years are still a matter of dispute Was the surface initially molten? Did the atmosphere contain ammonia, or methane? Everyone seems to agree, however, that the earth was a violent place with volcanic eruptions, lightning, and torrential rains There was little if any free oxygen and no layer of ozone to absorb the ultraviolet radiation from the sun The radiation, by its photochemical action, may have helped to keep the atmosphere rich in reactive molecules and far from chemical equilibrium Simple organic molecules (that is, molecules containing carbon) are likely to have been produced under such conditions The best evidence for this comes from laboratory experiments If mixtures of gases such as CO2, CH4, NH3, and H2 are heated with water and energized by electrical discharge or by ultraviolet radiation, they react to form small organic molecules usually a rather small selection, each made in large amounts (Figure 1-1) Among these products are compounds, such as hydrogen cyanide (HCN) and formaldehyde (HCHO), that readily undergo further reactions in aqueous solution (Figure 1-2) Most important, representatives of most of the major classes of small organic molecules found in cells are generated, including amino acids, sugars, and the purines and pyrimidines required to make nucleotides Although such experiments cannot reproduce the early conditions on the earth exactly, they make it plain that the formation of organic molecules is surprisingly easy And the developing earth had immense advantages over any human experimenter; it was very large and could produce a wide spectrum of conditions But above all, it had much more time - tens to hundreds of millions of years In such circumstances it seems very likely that, at some time and place, many of the simple organic molecules found in present-day cells accumulated in high concentrations Complex Chemical Systems Can Develop in an Environment That Is Far from Chemical Equilibrium Simple organic molecules such as amino acids and nucleotides can associate to form polymers file:///H|/albert/paginas/from_procaryotes_to_eucaryotes.htm (3 of 25) [29/05/2003 04:53:10 a.m.] ... 17 The Cell- Division Cycle Introduction The General Strategy of the Cell Cycle The Early Embryonic Cell Cycle and the Role of MPF Yeasts and the Molecular Genetics of Cell- Cycle Control Cell- Division... Defined the First Cell7 One of the crucial events leading to the formation of the first cell must have been the development of an outer membrane For example, the proteins synthesized under the control... Cited 15 Cell Signaling Introduction General Principles of Cell Signaling Signaling via G-Protein-linked Cell- Surface Receptors Signaling via Enzyme-linked Cell- Surface Receptors Target -Cell Adaptation