Essential Cell Biology, 4th Edition

Essential Cell Biology provides a readily accessible introduction to the central concepts of cell biology, and its lively, clear writing and exceptional illustrations make it the ideal textbook for a first course in both cell and molecular biology. The text and figures are easy-to-follow, accurate, clear, and engaging for the introductory student. Molecular detail has been kept to a minimum in order to provide the reader with a cohesive conceptual framework for the basic science that underlies our current understanding of all of biology, including the biomedical sciences. The Fourth Edition has been thoroughly revised, and covers the latest developments in this fast-moving field, yet retains the academic level and length of the previous edition. The book is accompanied by a rich package of online student and instructor resources, including over 130 narrated movies, an expanded and updated Question Bank. Essential Cell Biology, Fourth Edition is additionally supported by the Garland Science Learning System. This homework platform is designed to evaluate and improve student performance and allows instructors to select assignments on specific topics and review the performance of the entire class, as well as individual students, via the instructor dashboard. Students receive immediate feedback on their mastery of the topics, and will be better prepared for lectures and classroom discussions. The user-friendly system provides a convenient way to engage students while assessing progress. Performance data can be used to tailor classroom discussion, activities, and lectures to address students’ needs precisely and efficiently. For more information and sample material, visit http://garlandscience.rocketmix.com/. Copyright Preface Acknowledgments Resources for Instructors and Students Contents and Special Features Detailed Contents Chapter 1: Cells: The Fundamental Units of Life Unity and Diversity of Cells Cells Vary Enormously in Appearance and Function Living Cells All Have a Similar Basic Chemistry All Present-Day Cells Have Apparently Evolved from the Same Ancestral Cell Genes Provide the Instructions for Cell Form, Function, and Complex Behavior Cells Under the Microscope The Invention of the Light Microscope Led to the Discovery of Cells Light Microscopes Allow Examination of Cells and Some of Their Components The Fine Structure of a Cell Is Revealed by Electron Microscopy The Prokaryotic Cell Prokaryotes Are the Most Diverse and Numerous Cells on Earth The World of Prokaryotes Is Divided into Two Domains: Bacteria and Archaea The Eukaryotic Cell The Nucleus Is the Information Store of the Cell Mitochondria Generate Usable Energy from Food to Power the Cell Chloroplasts Capture Energy from Sunlight Internal Membranes Create Intracellular Compartments with Different Functions The Cytosol Is a Concentrated Aqueous Gel of Large and Small Molecules The Cytoskeleton Is Responsible for Directed Cell Movements The Cytoplasm Is Far from Static Eukaryotic Cells May Have Originated as Predators Model Organisms Molecular Biologists Have Focused on E. coli Brewer’s Yeast Is a Simple Eukaryotic Cell Arabidopsis Has Been Chosen as a Model Plant Model Animals Include Flies, Fish, Worms, and Mice Biologists Also Directly Study Human Beings and Their Cells Comparing Genome Sequences Reveals Life’s Common Heritage Genomes Contain More Than Just Genes Essential Concepts Key Terms Questions Chapter 2: Chemical Components of Cells Chemical Bonds Cells Are Made of Relatively Few Types of Atoms The Outermost Electrons Determine How Atoms Interact Covalent Bonds Form by the Sharing of Electrons There Are Different Types of Covalent Bonds Covalent Bonds Vary in Strength Ionic Bonds Form by the Gain and Loss of Electrons Noncovalent Bonds Help Bring Molecules Together in Cells Hydrogen Bonds Are Important Noncovalent Bonds For Many Biological Molecules Some Polar Molecules Form Acids and Bases in Water Small Molecules in Cells A Cell Is Formed from Carbon Compounds Cells Contain Four Major Families of Small Organic Molecules Sugars Are Both Energy Sources and Subunits of Polysaccharides Fatty Acid Chains Are Components of Cell Membranes Amino Acids Are the Subunits of Proteins Nucleotides Are the Subunits of DNA and RNA Macromolecules in Cells Each Macromolecule Contains a Specific Sequence of Subunits Noncovalent Bonds Specify the Precise Shape of a Macromolecule Noncovalent Bonds Allow a Macromolecule to Bind Other Selected Molecules Essential Concepts Key Terms Questions Chapter 3: Energy, Catalysis, and Biosynthesis The Use of Energy by Cells Biological Order Is Made Possible by the Release of Heat Energy from Cells Cells Can Convert Energy from One Form to Another Photosynthetic Organisms Use Sunlight to Synthesize Organic Molecules Cells Obtain Energy by the Oxidation of Organic Molecules Oxidation and Reduction Involve Electron Transfers Free Energy and Catalysis Chemical Reactions Proceed in the Direction that Causes a Loss of Free Energy Enzymes Reduce the Energy Needed to Initiate Spontaneous Reactions The Free-Energy Change for a Reaction Determines Whether It Can Occur ΔG Changes As a Reaction Proceeds Toward Equilibrium The Standard Free-Energy Change, ΔG°, Makes it Possible to Compare the Energetics of Different Reactions The Equilibrium Constant Is Directly Proportional to ΔG° In Complex Reactions, the Equilibrium Constant Includes the Concentrations of All Reactants and Products The Equilibrium Constant Indicates the Strength of Molecular Interactions For Sequential Reactions, the Changes in Free Energy Are Additive Thermal Motion Allows Enzymes to Find Their Substrates Vmax and KM Measure Enzyme Performance Activated Carriers and Biosynthesis The Formation of an Activated Carrier Is Coupled to an Energetically Favorable Reaction ATP Is the Most Widely Used Activated Carrier Energy Stored in ATP Is Often Harnessed to Join Two Molecules Together NADH and NADPH Are Both Activated Carriers of Electrons NADPH and NADH Have Different Roles in Cells Cells Make Use of Many Other Activated Carriers The Synthesis of Biological Polymers Requires an Energy Input Essential Concepts Key Terms Questions Chapter 4: Protein Structure and Function The Shape and Structure of Proteins The Shape of a Protein Is Specified by Its Amino Acid Sequence Proteins Fold into a Conformation of Lowest Energy Proteins Come in a Wide Variety of Complicated Shapes The α Helix and the β Sheet Are Common Folding Patterns Helices Form Readily in Biological Structures β Sheets Form Rigid Structures at the Core of Many Proteins Proteins Have Several Levels of Organization Many Proteins Also Contain Unstructured Regions Few of the Many Possible Polypeptide Chains Will Be Useful Proteins Can Be Classified into Families Large Protein Molecules Often Contain More Than One Polypeptide Chain Proteins Can Assemble into Filaments, Sheets, or Spheres Some Types of Proteins Have Elongated Fibrous Shapes Extracellular Proteins Are Often Stabilized by Covalent Cross-Linkages How Proteins Work All Proteins Bind to Other Molecules There Are Billions of Different Antibodies, Each with a Different Binding Site Enzymes Are Powerful and Highly Specific Catalysts Lysozyme Illustrates How an Enzyme Works Many Drugs Inhibit Enzymes Tightly Bound Small Molecules Add Extra Functions to Proteins How Proteins Are Controlled The Catalytic Activities of Enzymes Are Often Regulated by Other Molecules Allosteric Enzymes Have Two or More Binding Sites That Influence One Another Phosphorylation Can Control Protein Activity by Causing a Conformational Change Covalent Modifications Also Control the Location and Interaction of Proteins GTP-Binding Proteins Are Also Regulated by the Cyclic Gain and Loss of a Phosphate Group ATP Hydrolysis Allows Motor Proteins to Produce Directed Movements in Cells Proteins Often Form Large Complexes That Function as Protein Machines How Proteins Are Studied Proteins Can be Purified from Cells or Tissues Determining a Protein’s Structure Begins with Determining Its Amino Acid Sequence Genetic Engineering Techniques Permit the Large-Scale Production, Design, and Analysis of Almost Any Protein The Relatedness of Proteins Aids the Prediction of Protein Structure and Function Essential Concepts Key Terms Questions Chapter 5: DNA and Chromosomes The Structure of DNA A DNA Molecule Consists of Two Complementary Chains of Nucleotides The Structure of DNA Provides a Mechanism for Heredity The Structure of Eukaryotic Chromosomes Eukaryotic DNA Is Packaged into Multiple Chromosomes Chromosomes Contain Long Strings of Genes Specialized DNA Sequences Are Required for DNA Replication and Chromosome Segregation Interphase Chromosomes Are Not Randomly Distributed Within the Nucleus The DNA in Chromosomes Is Always Highly Condensed Nucleosomes Are the Basic Units of Eukaryotic Chromosome Structure Chromosome Packing Occurs on Multiple Levels The Regulation of Chromosome Structure Changes in Nucleosome Structure Allow Access to DNA Interphase Chromosomes Contain Both Condensed and More Extended Forms of Chromatin Essential Concepts Key Terms Questions Chapter 6: DNA Replication, Repair, and Recombination DNA Replication Base-Pairing Enables DNA Replication DNA Synthesis Begins at Replication Origins Two Replication Forks Form at Each Replication Origin DNA Polymerase Synthesizes DNA Using a Parental Strand as Template The Replication Fork Is Asymmetrical DNA Polymerase Is Self-correcting Short Lengths of RNA Act as Primers for DNA Synthesis Proteins at a Replication Fork Cooperate to Form a Replication Machine Telomerase Replicates the Ends of Eukaryotic Chromosomes DNA Repair DNA Damage Occurs Continually in Cells Cells Possess a Variety of Mechanisms for Repairing DNA A DNA Mismatch Repair System Removes Replication Errors That Escape Proofreading Double-Strand DNA Breaks Require a Different Strategy for Repair Homologous Recombination Can Flawlessly Repair DNA Double-Strand Breaks Failure to Repair DNA Damage Can Have Severe Consequences for a Cell or Organism A Record of the Fidelity of DNA Replication and Repair Is Preserved in Genome Sequences Essential Concepts Key Terms Questions Chapter 7: From DNA to Protein: How Cells Read the Genome From DNA to RNA Portions of DNA Sequence Are Transcribed into RNA Transcription Produces RNA That Is Complementary to One Strand of DNA Cells Produce Various Types of RNA Signals in DNA Tell RNA Polymerase Where to Start and Finish Transcription Initiation of Eukaryotic Gene Transcription Is a Complex Process Eukaryotic RNA Polymerase Requires General Transcription Factors Eukaryotic mRNAs Are Processed in the Nucleus In Eukaryotes, Protein-Coding Genes Are Interrupted by Noncoding Sequences Called Introns Introns Are Removed From Pre-mRNAs by RNA Splicing Mature Eukaryotic mRNAs Are Exported from the Nucleus mRNA Molecules Are Eventually Degraded in the Cytosol The Earliest Cells May Have Had Introns in Their Genes From RNA to Protein An mRNA Sequence Is Decoded in Sets of Three Nucleotides tRNA Molecules Match Amino Acids to Codons in mRNA Specific Enzymes Couple tRNAs to the Correct Amino Acid The mRNA Message Is Decoded by Ribosomes The Ribosome Is a Ribozyme Specific Codons in mRNA Signal the Ribosome Where to Start and to Stop Protein Synthesis Proteins Are Made on Polyribosomes Inhibitors of Prokaryotic Protein Synthesis Are Used as Antibiotics Controlled Protein Breakdown Helps Regulate the Amount of Each Protein in a Cell There Are Many Steps Between DNA and Protein RNA and the Origins of Life Life Requires Autocatalysis RNA Can Both Store Information and Catalyze Chemical Reactions RNA Is Thought to Predate DNA in Evolution Essential Concepts Key Terms Questions Chapter 8: Control of Gene Expression An Overview of Gene Expression The Different Cell Types of a Multicellular Organism Contain the Same DNA Different Cell Types Produce Different Sets of Proteins A Cell Can Change the Expression of Its Genes in Response to External Signals Gene Expression Can Be Regulated at Various Steps from DNA to RNA to Protein How Transcriptional Switches Work Transcription Regulators Bind to Regulatory DNA Sequences Transcriptional Switches Allow Cells to Respond to Changes in Their Environment Repressors Turn Genes Off and Activators Turn Them On An Activator and a Repressor Control the Lac Operon Eukaryotic Transcription Regulators Control Gene Expression from a Distance Eukaryotic Transcription Regulators Help Initiate Transcription by Recruiting Chromatin-Modifying Proteins The Molecular Mechanisms That Create Specialized Cell Types Eukaryotic Genes Are Controlled by Combinations of Transcription Regulators The Expression of Different Genes Can Be Coordinated by a Single Protein Combinatorial Control Can Also Generate Different Cell Types Specialized Cell Types Can Be Experimentally Reprogrammed to Become Pluripotent Stem Cells The Formation of an Entire Organ Can Be Triggered by a Single Transcription Regulator Epigenetic Mechanisms Allow Differentiated Cells to Maintain Their Identity Post-Transcriptional Controls Each mRNA Controls Its Own Degradation and Translation Regulatory RNAs Control the Expression of Thousands of Genes MicroRNAs Direct the Destruction of Target mRNAs Small Interfering RNAs Are Produced From Double-Stranded, Foreign RNAs to Protect Cells From Infections Thousands of Long Noncoding RNAs May Also Regulate Mammalian Gene Activity Essential Concepts Key Terms Questions Chapter 9: How Genes and Genomes Evolve Generating Genetic Variation In Sexually Reproducing Organisms, Only Changes to the Germ Line Are Passed On To Progeny Point Mutations Are Caused by Failures of the Normal Mechanisms for Copying and Repairing DNA Point Mutations Can Change the Regulation of a Gene DNA Duplications Give Rise to Families of Related Genes The Evolution of the Globin Gene Family Shows How Gene Duplication and Divergence Can Produce New Proteins Whole-Genome Duplications Have Shaped the Evolutionary History of Many Species Novel Genes Can Be Created by Exon Shuffling The Evolution of Genomes Has Been Profoundly Influenced by the Movement of Mobile Genetic Elements Genes Can Be Exchanged Between Organisms by Horizontal Gene Transfer Reconstructing Life’s Family Tree Genetic Changes That Provide a Selective Advantage Are Likely to Be Preserved Closely Related Organisms Have Genomes That Are Similar in Organization As Well As Sequence Functionally Important Genome Regions Show Up As Islands of Conserved DNA Sequence Genome Comparisons Show That Vertebrate Genomes Gain and Lose DNA Rapidly Sequence Conservation Allows Us to Trace Even the Most Distant Evolutionary Relationships Transposons and Viruses Mobile Genetic Elements Encode the Components They Need for Movement The Human Genome Contains Two Major Families of Transposable Sequences Viruses Can Move Between Cells and Organisms Retroviruses Reverse the Normal Flow of Genetic Information Examining the Human Genome The Nucleotide Sequences of Human Genomes Show How Our Genes Are Arranged Accelerated Changes in Conserved Genome Sequences Help Reveal What Makes Us Human Genome Variation Contributes to Our Individuality—But How? Differences in Gene Regulation May Help Explain How Animals With Similar Genomes Can Be So Different Essential Concepts Key Terms Questions Chapter 10: Modern Recombinant DNA Technology Manipulating and Analyzing DNA Molecules Restriction Nucleases Cut DNA Molecules at Specific Sites Gel Electrophoresis Separates DNA Fragments of Different Sizes Bands of DNA in a Gel Can Be Visualized Using Fluorescent Dyes or Radioisotopes Hybridization Provides a Sensitive Way to Detect Specific Nucleotide Sequences DNA Cloning in Bacteria DNA Cloning Begins with Genome Fragmentation and Production of Recombinant DNAs Recombinant DNA Can Be Inserted Into Plasmid Vectors Recombinant DNA Can Be Copied Inside Bacterial Cells Genes Can Be Isolated from a DNA Library cDNA Libraries Represent the mRNAs Produced by Particular Cells DNA Cloning by PCR PCR Uses a DNA Polymerase to Amplify Selected DNA Sequences in a Test Tube Multiple Cycles of Amplification In Vitro Generate Billions of Copies of the Desired Nucleotide Sequence PCR is Also Used for Diagnostic and Forensic Applications Exploring and Exploiting Gene function Whole Genomes Can Be Sequenced Rapidly Next-Generation Sequencing Techniques Make Genome Sequencing Faster and Cheaper Comparative Genome Analyses Can Identify Genes and Predict Their Function Analysis of mRNAs By Microarray or RNA-Seq Provides a Snapshot of Gene Expression In Situ Hybridization Can Reveal When and Where a Gene Is Expressed Reporter Genes Allow Specific Proteins to be Tracked in Living Cells The Study of Mutants Can Help Reveal the Function of a Gene RNA Interference (RNAi) Inhibits the Activity of Specific Genes A Known Gene Can Be Deleted or Replaced With an Altered Version Mutant Organisms Provide Useful Models of Human Disease Transgenic Plants Are Important for Both Cell Biology and Agriculture Even Rare Proteins Can Be Made in Large Amounts Using Cloned DNA Essential Concepts Key terms Questions Chapter 11: Membrane Structure The Lipid Bilayer Membrane Lipids Form Bilayers in Water The Lipid Bilayer Is a Flexible Two-dimensional Fluid The Fluidity of a Lipid Bilayer Depends on Its Composition Membrane Assembly Begins in the ER Certain Phospholipids Are Confined to One Side of the Membrane Membrane Proteins Membrane Proteins Associate with the Lipid Bilayer in Different Ways A Polypeptide Chain Usually Crosses the Lipid Bilayer as an α Helix Membrane Proteins Can Be Solubilized in Detergents We Know the Complete Structure of Relatively Few Membrane Proteins The Plasma Membrane Is Reinforced by the Underlying Cell Cortex A Cell Can Restrict the Movement of Its Membrane Proteins The Cell Surface Is Coated with Carbohydrate Essential Concepts Key Terms Questions Chapter 12: Transport Across Cell Membranes Principles of Transmembrane Transport Lipid Bilayers Are Impermeable to Ions and Most Uncharged Polar Molecules The Ion Concentrations Inside a Cell Are Very Different from Those Outside Differences in the Concentration of Inorganic Ions Across a Cell Membrane Create a Membrane Potential Cells Contain Two Classes of Membrane Transport Proteins: Transporters and Channels Solutes Cross Membranes by Either Passive or Active Transport Both the Concentration Gradient and Membrane Potential Influence the Passive Transport of Charged Solutes Water Moves Passively Across Cell Membranes Down Its Concentration Gradient—a Process Called Osmosis Transporters and Their Functions Passive Transporters Move a Solute Along Its Electrochemical Gradient Pumps Actively Transport a Solute Against Its Electrochemical Gradient The Na+ Pump in Animal Cells Uses Energy Supplied by ATP to Expel Na+ and Bring in K+ The Na+ Pump Generates a Steep Concentration Gradient of Na+ Across the Plasma Membrane Ca2+ Pumps Keep the Cytosolic Ca2+ Concentration Low Coupled Pumps Exploit Solute Gradients to Mediate Active Transport The Electrochemical Na+ Gradient Drives Coupled Pumps in the Plasma Membrane of Animal Cells Electrochemical H+ Gradients Drive Coupled Pumps in Plants, Fungi, and Bacteria Ion Channels and the Membrane Potential Ion Channels Are Ion-selective and Gated Membrane Potential Is Governed by the Permeability of a Membrane to Specific Ions Ion Channels Randomly Snap Between Open and Closed States Different Types of Stimuli Influence the Opening and Closing of Ion Channels Voltage-gated Ion Channels Respond to the Membrane Potential Ion Channels and Nerve Cell Signaling Action Potentials Allow Rapid Long-Distance Communication Along Axons Action Potentials Are Mediated by Voltage-gated Cation Channels Voltage-gated Ca2+ Channels in Nerve Terminals Convert an Electrical Signal into a Chemical Signal Transmitter-gated Ion Channels in the Postsynaptic Membrane Convert the Chemical Signal Back into an Electrical Signal Neurotransmitters Can Be Excitatory or Inhibitory Most Psychoactive Drugs Affect Synaptic Signaling by Binding to Neurotransmitter Receptors The Complexity of Synaptic Signaling Enables Us to Think, Act, Learn, and Remember Optogenetics Uses Light-gated Ion Channels to Transiently Activate or Inactivate Neurons in Living Animals Essential Concepts Key Terms Questions Chapter 13: How Cells Obtain Energy From Food The Breakdown and Utilization of Sugars and Fats Food Molecules Are Broken Down in Three Stages Glycolysis Extracts Energy from the Splitting of Sugar Glycolysis Produces Both ATP and NADH Fermentations Can Produce ATP in the Absence of Oxygen Glycolytic Enzymes Couple Oxidation to Energy Storage in Activated Carriers Several Organic Molecules Are Converted to Acetyl CoA in the Mitochondrial Matrix The Citric Acid Cycle Generates NADH by Oxidizing Acetyl Groups to CO2 Many Biosynthetic Pathways Begin with Glycolysis or the Citric Acid Cycle Electron Transport Drives the Synthesis of the Majority of the ATP in Most Cells Regulation of Metabolism Catabolic and Anabolic Reactions Are Organized and Regulated Feedback Regulation Allows Cells to Switch from Glucose Breakdown to Glucose Synthesis Cells Store Food Molecules in Special Reservoirs to Prepare for Periods of Need Essential Concepts Key Terms Questions Chapter 14: Energy Generation in Mitochondria and Chloroplasts Cells Obtain Most of Their Energy by a Membrane-based Mechanism Chemiosmotic Coupling is an Ancient Process, Preserved in Present-Day Cells Mitochondria and Oxidative Phosphorylation Mitochondria Can Change Their Shape, Location, and Number to Suit a Cell’s Needs A Mitochondrion Contains an Outer Membrane, an Inner Membrane, and Two Internal Compartments The Citric Acid Cycle Generates the High-Energy Electrons Required for ATP Production The Movement of Electrons is Coupled to the Pumping of Protons Protons Are Pumped Across the Inner Mitochondrial Membrane by Proteins in the Electron-Transport Chain Proton Pumping Produces a Steep Electrochemical Proton Gradient Across the Inner Mitochondrial Membrane ATP Synthase Uses the Energy Stored in the Electrochemical Proton Gradient to Produce ATP Coupled Transport Across the Inner Mitochondrial Membrane Is Also Driven by the Electrochemical Proton Gradient The Rapid Conversion of ADP to ATP in Mitochondria Maintains a High ATP/ADP Ratio in Cells Cell Respiration Is Amazingly Efficient Molecular Mechanisms of Electron Transport and Proton Pumping Protons Are Readily Moved by the Transfer of Electrons The Redox Potential Is a Measure of Electron Affinities Electron Transfers Release Large Amounts of Energy Metals Tightly Bound to Proteins Form Versatile Electron Carriers Cytochrome c Oxidase Catalyzes the Reduction of Molecular Oxygen Chloroplasts and Photosynthesis Chloroplasts Resemble Mitochondria but Have an Extra Compartment—the Thylakoid Photosynthesis Generates—Then Consumes—ATP and NADPH Chlorophyll Molecules Absorb the Energy of Sunlight Excited Chlorophyll Molecules Funnel Energy into a Reaction Center A Pair of Photosystems Cooperate to Generate Both ATP and NADPH Oxygen Is Generated by a Water-Splitting Complex Associated with Photosystem II The Special Pair in Photosystem I Receives its Electrons from Photosystem II Carbon Fixation Uses ATP and NADPH to Convert CO2 into Sugars Sugars Generated by Carbon Fixation Can Be Stored As Starch or Consumed to Produce ATP The Evolution of Energy-Generating Systems Oxidative Phosphorylation Evolved in Stages Photosynthetic Bacteria Made Even Fewer Demands on Their Environment The Lifestyle of Methanococcus Suggests That Chemiosmotic Coupling Is an Ancient Process Essential Concepts Key Terms Questions Chapter 15: Intracellular Compartments and Protein Transport Membrane-enclosed Organelles Eukaryotic Cells Contain a Basic Set of Membrane-enclosed Organelles Membrane-enclosed Organelles Evolved in Different Ways Protein Sorting Proteins Are Transported into Organelles by Three Mechanisms Signal Sequences Direct Proteins to the Correct Compartment Proteins Enter the Nucleus Through Nuclear Pores Proteins Unfold to Enter Mitochondria and Chloroplasts Proteins Enter Peroxisomes from Both the Cytosol and the Endoplasmic Reticulum Proteins Enter the Endoplasmic Reticulum While Being Synthesized Soluble Proteins Made on the ER Are Released into the ER Lumen Start and Stop Signals Determine the Arrangement of a Transmembrane Protein in the Lipid Bilayer Vesicular Transport Transport Vesicles Carry Soluble Proteins and Membrane Between Compartments Vesicle Budding Is Driven by the Assembly of a Protein Coat Vesicle Docking Depends on Tethers and SNAREs Secretory Pathways Most Proteins Are Covalently Modified in the ER Exit from the ER Is Controlled to Ensure Protein Quality The Size of the ER Is Controlled by the Demand for Protein Proteins Are Further Modified and Sorted in the Golgi Apparatus Secretory Proteins Are Released from the Cell by Exocytosis Endocytic Pathways Specialized Phagocytic Cells Ingest Large Particles Fluid and Macromolecules Are Taken Up by Pinocytosis Receptor-mediated Endocytosis Provides a Specific Route into Animal Cells Endocytosed Macromolecules Are Sorted in Endosomes Lysosomes Are the Principal Sites of Intracellular Digestion Essential Concepts Key Terms Questions Chapter 16: Cell Signaling General Principles of Cell Signaling Signals Can Act over a Long or Short Range Each Cell Responds to a Limited Set of Extracellular Signals, Depending on Its History and Its Current State A Cell’s Response to a Signal Can Be Fast or Slow Some Hormones Cross the Plasma Membrane and Bind to Intracellular Receptors Some Dissolved Gases Cross the Plasma Membrane and Activate Intracellular Enzymes Directly Cell-Surface Receptors Relay Extracellular Signals via Intracellular Signaling Pathways Some Intracellular Signaling Proteins Act as Molecular Switches Cell-Surface Receptors Fall into Three Main Classes Ion-channel–coupled Receptors Convert Chemical Signals into Electrical Ones G-protein-coupled Receptors Stimulation of GPCRs Activates G-Protein Subunits Some Bacterial Toxins Cause Disease by Altering the Activity of G Proteins Some G Proteins Directly Regulate Ion Channels Many G Proteins Activate Membrane-bound Enzymes that Produce Small Messenger Molecules The Cyclic AMP Signaling Pathway Can Activate Enzymes and Turn On Genes The Inositol Phospholipid Pathway Triggers a Rise in Intracellular Ca2+ A Ca2+ Signal Triggers Many Biological Processes GPCR-Triggered Intracellular Signaling Cascades Can Achieve Astonishing Speed, Sensitivity, and Adaptability Enzyme-coupled Receptors Activated RTKs Recruit a Complex of Intracellular Signaling Proteins Most RTKs Activate the Monomeric GTPase Ras RTKs Activate PI 3-Kinase to Produce Lipid Docking Sites in the Plasma Membrane Some Receptors Activate a Fast Track to the Nucleus Cell–Cell Communication Evolved Independently in Plants and Animals Protein Kinase Networks Integrate Information to Control Complex Cell Behaviors Essential Concepts Key Terms Questions Chapter 17: Cytoskeleton Intermediate Filaments Intermediate Filaments Are Strong and Ropelike Intermediate Filaments Strengthen Cells Against Mechanical Stress The Nuclear Envelope Is Supported by a Meshwork of Intermediate Filaments Microtubules Microtubules Are Hollow Tubes with Structurally Distinct Ends The Centrosome Is the Major Microtubule-organizing Center in Animal Cells Growing Microtubules Display Dynamic Instability Dynamic Instability is Driven by GTP Hydrolysis Microtubule Dynamics Can be Modified by Drugs Microtubules Organize the Cell Interior Motor Proteins Drive Intracellular Transport Microtubules and Motor Proteins Position Organelles in the Cytoplasm Cilia and Flagella Contain Stable Microtubules Moved by Dynein Actin Filaments Actin Filaments Are Thin and Flexible Actin and Tubulin Polymerize by Similar Mechanisms Many Proteins Bind to Actin and Modify Its Properties A Cortex Rich in Actin Filaments Underlies the Plasma Membrane of Most Eukaryotic Cells Cell Crawling Depends on Cortical Actin Actin Associates with Myosin to Form Contractile Structures Extracellular Signals Can Alter the Arrangement of Actin Filaments Muscle Contraction Muscle Contraction Depends on Interacting Filaments of Actin and Myosin Actin Filaments Slide Against Myosin Filaments During Muscle Contraction Muscle Contraction Is Triggered by a Sudden Rise in Cytosolic Ca2+ Different Types of Muscle Cells Perform Different Functions Essential Concepts Key Terms Questions Chapter 18: The Cell-Division Cycle Overview of the Cell Cycle The Eukaryotic Cell Cycle Usually Includes Four Phases A Cell-Cycle Control System Triggers the Major Processes of the Cell Cycle Cell-Cycle Control is Similar in All Eukaryotes The Cell-Cycle Control System The Cell-Cycle Control System Depends on Cyclically Activated Protein Kinases called Cdks Different Cyclin–Cdk Complexes Trigger Different Steps in the Cell Cycle Cyclin Concentrations are Regulated by Transcription and by Proteolysis The Activity of Cyclin–Cdk Complexes Depends on Phosphorylation and Dephosphorylation Cdk Activity Can be Blocked by Cdk Inhibitor Proteins The Cell-Cycle Control System Can Pause the Cycle in Various Ways G1 PHASE Cdks are Stably Inactivated in G1 Mitogens Promote the Production of the Cyclins that Stimulate Cell Division DNA Damage Can Temporarily Halt Progression Through G1 Cells Can Delay Division for Prolonged Periods by Entering Specialized Nondividing States S Phase S-Cdk Initiates DNA Replication and Blocks Re-Replication Incomplete Replication Can Arrest the Cell Cycle in G2 M Phase M-Cdk Drives Entry Into M Phase and Mitosis Cohesins and Condensins Help Configure Duplicated Chromosomes for Separation Different Cytoskeletal Assemblies Carry Out Mitosis and Cytokinesis M Phase Occurs in Stages Mitosis Centrosomes Duplicate To Help Form the Two Poles of the Mitotic Spindle The Mitotic Spindle Starts to Assemble in Prophase Chromosomes Attach to the Mitotic Spindle at Prometaphase Chromosomes Assist in the Assembly of the Mitotic Spindle Chromosomes Line Up at the Spindle Equator at Metaphase Proteolysis Triggers Sister-Chromatid Separation at Anaphase Chromosomes Segregate During Anaphase An Unattached Chromosome Will Prevent Sister-Chromatid Separation The Nuclear Envelope Re-forms at Telophase Cytokinesis The Mitotic Spindle Determines the Plane of Cytoplasmic Cleavage The Contractile Ring of Animal Cells Is Made of Actin and Myosin Filaments Cytokinesis in Plant Cells Involves the Formation of a New Cell Wall Membrane-Enclosed Organelles Must Be Distributed to Daughter Cells When a Cell Divides Control of Cell Numbers and Cell Size Apoptosis Helps Regulate Animal Cell Numbers Apoptosis Is Mediated by an Intracellular Proteolytic Cascade The Intrinsic Apoptotic Death Program Is Regulated by the Bcl2 Family of Intracellular Proteins Extracellular Signals Can Also Induce Apoptosis Animal Cells Require Extracellular Signals to Survive, Grow, and Divide Survival Factors Suppress Apoptosis Mitogens Stimulate Cell Division by Promoting Entry into S Phase Growth Factors Stimulate Cells to Grow Some Extracellular Signal Proteins Inhibit Cell Survival, Division, or Growth Essential Concepts Key Terms Questions Chapter 19: Sexual Reproduction and the Power of Genetics The Benefits of Sex Sexual Reproduction Involves Both Diploid and Haploid Cells Sexual Reproduction Generates Genetic Diversity Sexual Reproduction Gives Organisms a Competitive Advantage in a Changing Environment Meiosis and Fertilization Meiosis Involves One Round of DNA __Essential Cell Biology__ provides a readily accessible introduction to the central concepts of cell biology, and its lively, clear writing and exceptional illustrations make it the ideal textbook for a first course in both cell and molecular biology. The text and figures are easy-to-follow, accurate, clear, and engaging for the introductory student. Molecular detail has been kept to a minimum in order to provide the reader with a cohesive conceptual framework for the basic science that underlies our current understanding of all of biology, including the biomedical sciences. The Fourth Edition has been thoroughly revised, and covers the latest developments in this fast-moving field, yet retains the academic level and length of the previous edition. The book is accompanied by a rich package of online student and instructor resources, including over 130 narrated movies, an expanded and updated Question Bank, and new enhanced assessments for students.