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Test Bank (Download Only) for Biochemistry 9th Edition by Lubert Stryer Jeremy Berg John Tymoczko Gregory Gatto ISBN: 9781319342906

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Test Bank for Biochemistry 9th Edition Stryer

Test Bank for Biochemistry 9th Edition by Lubert Stryer, Jeremy Berg, John Tymoczko, Gregory Gatto, ISBN: 9781319342906

Table of Contents

Part I THE MOLECULAR DESIGN OF LIFE
Chapter 1 Biochemistry: An Evolving Science
1.1 Biochemical Unity Underlies Biological Diversity
1.2 DNA Illustrates the Interplay Between Form and Function
DNA is constructed from four building blocks
Two single strands of DNA combine to form a double helix
DNA structure explains heredity and the storage of information
1.3 Concepts from Chemistry Explain the Properties of Biological Molecules
The formation of the DNA double helix as a key example
The double helix can form from its component strands
Covalent and noncovalent bonds are important for the structure and stability of biological molecules
The double helix is an expression of the rules of chemistry
The laws of thermodynamics govern the behavior of biochemical systems
Heat is released in the formation of the double helix
Acid–base reactions are central in many biochemical processes
Acid–base reactions can disrupt the double helix
Buffers regulate pH in organisms and in the laboratory
1.4 The Genomic Revolution Is Transforming Biochemistry, Medicine, and Other Fields
Genome sequencing has transformed biochemistry and other fields
Environmental factors influence human biochemistry
Genome sequences encode proteins and patterns of expression
APPENDIX Visualizing Molecular Structures: Small Molecules
APPENDIX Functional Groups
Chapter 2 Protein Composition and Structure
2.1 Proteins Are Built from a Repertoire of 20 Amino Acids
2.2 Primary Structure: Amino Acids Are Linked by Peptide Bonds to Form Polypeptide Chains
Proteins have unique amino acid sequences specified by genes
Polypeptide chains are flexible yet conformationally restricted
2.3 Secondary Structure: Polypeptide Chains Can Fold into Regular Structures Such As the Alpha Helix, the Beta Sheet, and Turns and Loops
The alpha helix is a coiled structure stabilized by intrachain hydrogen bonds
Beta sheets are stabilized by hydrogen bonding between polypeptide strands
Polypeptide chains can change direction by making reverse turns and loops
2.4 Tertiary Structure: Proteins Can Fold into Globular or Fibrous Structures
Fibrous proteins provide structural support for cells and tissues
2.5 Quaternary Structure: Polypeptide Chains Can Assemble into Multisubunit Structures
2.6 The Amino Acid Sequence of a Protein Determines Its Three-Dimensional Structure
Amino acids have different propensities for forming 〈 helices, ® sheets, and turns
Protein folding is a highly cooperative process
Proteins fold by progressive stabilization of intermediates rather than by random search
Prediction of three-dimensional structure from sequence remains a great challenge
Some proteins are inherently unstructured and can exist in multiple conformations
Protein misfolding and aggregation are associated with some neurological diseases
Posttranslational modifications confer new capabilities to proteins
APPENDIX Visualizing Molecular Structures: Proteins
Chapter 3 Exploring Proteins and Proteomes
3.1 The Purification of Proteins Is an Essential First Step in Understanding Their Function
The assay: How do we recognize the protein that we are looking for?
Proteins must be released from the cell to be purified
Proteins can be purified according to solubility, size, charge, and binding affinity
Proteins can be separated by gel electrophoresis and displayed
A protein purification scheme can be quantitatively evaluated
Ultracentrifugation is valuable for separating biomolecules and determining their masses
Protein purification can be made easier with the use of recombinant DNA technology
3.2 Immunology Provides Important Techniques with Which to Investigate Proteins
Antibodies to specific proteins can be generated
Monoclonal antibodies with virtually any desired specificity can be readily prepared
Proteins can be detected and quantified by using an enzyme-linked immunosorbent assay
Western blotting permits the detection of proteins separated by gel electrophoresis
Co-immunoprecipitation enables the identification of binding partners of a protein
Fluorescent markers make the visualization of proteins in the cell possible
3.3 Mass Spectrometry Is a Powerful Technique for the Identification of Peptides and Proteins
Peptides can be sequenced by mass spectrometry
Proteins can be specifically cleaved into small peptides to facilitate analysis
Genomic and proteomic methods are complementary
The amino acid sequence of a protein provides valuable information
Individual proteins can be identified by mass spectrometry
3.4 Peptides Can Be Synthesized by Automated Solid-Phase Methods
3.5 Three-Dimensional Protein Structure Can Be Determined by X-ray Crystallography, NMR Spectroscopy, and Cryo-Electron Microscopy
X-ray crystallography reveals three-dimensional structure in atomic detail
Nuclear magnetic resonance spectroscopy can reveal the structures of proteins in solution
Cryo-electron microscopy is an emerging method of protein structure determination
APPENDIX Problem-Solving Strategies
Chapter 4 DNA, RNA, and the Flow of Genetic Information
4.1 A Nucleic Acid Consists of Four Kinds of Bases Linked to a Sugar–Phosphate Backbone
RNA and DNA differ in the sugar component and one of the bases
Nucleotides are the monomeric units of nucleic acids
DNA molecules are very long and have directionality
4.2 A Pair of Nucleic Acid Strands with Complementary Sequences Can Form a Double-Helical Structure
The double helix is stabilized by hydrogen bonds and van der Waals interactions
DNA can assume a variety of structural forms
Some DNA molecules are circular and supercoiled
Single-stranded nucleic acids can adopt elaborate structures
4.3 The Double Helix Facilitates the Accurate Transmission of Hereditary Information
Differences in DNA density established the validity of the semiconservative replication hypothesis
The double helix can be reversibly melted
Unusual circular DNA exists in the eukaryotic nucleus
4.4 DNA Is Replicated by Polymerases That Take Instructions from Templates
DNA polymerase catalyzes phosphodiester-bridge formation
The genes of some viruses are made of RNA
4.5 Gene Expression Is the Transformation of DNA Information into Functional Molecules
Several kinds of RNA play key roles in gene expression
All cellular RNA is synthesized by RNA polymerases
RNA polymerases take instructions from DNA templates
Transcription begins near promoter sites and ends at terminator sites
Transfer RNAs are the adaptor molecules in protein synthesis
4.6 Amino Acids Are Encoded by Groups of Three Bases Starting from a Fixed Point
Major features of the genetic code
Messenger RNA contains start and stop signals for protein synthesis
The genetic code is nearly universal
4.7 Most Eukaryotic Genes Are Mosaics of Introns and Exons
RNA processing generates mature RNA
Many exons encode protein domains
APPENDIX Problem-Solving Strategies
Chapter 5 Exploring Genes and Genomes
5.1 The Exploration of Genes Relies on Key Tools
Restriction enzymes split DNA into specific fragments
Restriction fragments can be separated by gel electrophoresis and visualized
DNA can be sequenced by controlled termination of replication
DNA probes and genes can be synthesized by automated solid-phase methods
Selected DNA sequences can be greatly amplified by the polymerase chain reaction
PCR is a powerful technique in medical diagnostics, forensics, and studies of molecular evolution
The tools for recombinant DNA technology have been used to identify disease-causing mutations
5.2 Recombinant DNA Technology Has Revolutionized All Aspects of Biology
Restriction enzymes and DNA ligase are key tools in forming recombinant DNA molecules
Plasmids and ⎣ phage are choice vectors for DNA cloning in bacteria
Bacterial and yeast artificial chromosomes
Specific genes can be cloned from digests of genomic DNA
Complementary DNA prepared from mRNA can be expressed in host cells
Proteins with new functions can be created through directed changes in DNA
Recombinant methods enable the exploration of the functional effects of disease-causing mutations
5.3 Complete Genomes Have Been Sequenced and Analyzed
The genomes of organisms ranging from bacteria to multicellular eukaryotes have been sequenced
The sequence of the human genome has been completed
Next-generation sequencing methods enable the rapid determination of a complete genome sequence
Comparative genomics has become a powerful research tool
5.4 Eukaryotic Genes Can Be Quantitated and Manipulated with Considerable Precision
Gene-expression levels can be comprehensively examined
New genes inserted into eukaryotic cells can be efficiently expressed
Transgenic animals harbor and express genes introduced into their germ lines
Gene disruption and genome editing provide clues to gene function and opportunities for new therapies
RNA interference provides an additional tool for disrupting gene expression
Tumor-inducing plasmids can be used to introduce new genes into plant cells
Human gene therapy holds great promise for medicine
APPENDIX Biochemistry in Focus: Improved biofuel production from genetically-engineered algae
Chapter 6 Exploring Evolution and Bioinformatics
6.1 Homologs Are Descended from a Common Ancestor
6.2 Statistical Analysis of Sequence Alignments Can Detect Homology
The statistical significance of alignments can be estimated by shuffling
Distant evolutionary relationships can be detected through the use of substitution matrices
Databases can be searched to identify homologous sequences
6.3 Examination of Three-Dimensional Structure Enhances Our Understanding of Evolutionary Relationships
Tertiary structure is more conserved than primary structure
Knowledge of three-dimensional structures can aid in the evaluation of sequence alignments
Repeated motifs can be detected by aligning sequences with themselves
Convergent evolution illustrates common solutions to biochemical challenges
Comparison of RNA sequences can be a source of insight into RNA secondary structures
6.4 Evolutionary Trees Can Be Constructed on the Basis of Sequence Information
Horizontal gene transfer events may explain unexpected branches of the evolutionary tree
6.5 Modern Techniques Make the Experimental Exploration of Evolution Possible
Ancient DNA can sometimes be amplified and sequenced
Molecular evolution can be examined experimentally
APPENDIX Biochemistry in Focus: Using sequence alignments to identify functionally important residues
APPENDIX Problem-Solving Strategies
Chapter 7 Hemoglobin: Portrait of a Protein in Action
7.1  Binding of Oxygen by Heme Iron
Changes in heme electronic structure upon oxygen binding are the basis for functional imaging studies
The structure of myoglobin prevents the release of reactive oxygen species
Human hemoglobin is an assembly of four myoglobin-like subunits
7.2 Hemoglobin Binds Oxygen Cooperatively
Oxygen binding markedly changes the quaternary structure of hemoglobin
Hemoglobin cooperativity can be potentially explained by several models
Structural changes at the heme groups are transmitted to the 〈1®1–〈2®2 interface
2,3-Bisphosphoglycerate in red cells is crucial in determining the oxygen affinity of hemoglobin
Carbon monoxide can disrupt oxygen transport by hemoglobin
7.3 Hydrogen Ions and Carbon Dioxide Promote the Release of Oxygen: The Bohr Effect
7.4 Mutations in Genes Encoding Hemoglobin Subunits Can Result in Disease
Sickle-cell anemia results from the aggregation of mutated deoxyhemoglobin molecules
Thalassemia is caused by an imbalanced production of hemoglobin chains
The accumulation of free alpha-hemoglobin chains is prevented
Additional globins are encoded in the human genome
APPENDIX Binding Models Can Be Formulated in Quantitative Terms: The Hill Plot and the Concerted Model
APPENDIX Biochemistry in Focus: A potential antidote for carbon monoxide poisoning?
Chapter 8 Enzymes: Basic Concepts and Kinetics
8.1 Enzymes are Powerful and Highly Specific Catalysts
Many enzymes require cofactors for activity
Enzymes can transform energy from one form into another
8.2 Gibbs Free Energy Is a Useful Thermodynamic Function for Understanding Enzymes
The free-energy change provides information about the spontaneity but not the rate of a reaction
The standard free-energy change of a reaction is related to the equilibrium constant
Enzymes alter only the reaction rate and not the reaction equilibrium
8.3 Enzymes Accelerate Reactions by Facilitating the Formation of the Transition State
The formation of an enzyme–substrate complex is the first step in enzymatic catalysis
The active sites of enzymes have some common features
The binding energy between enzyme and substrate is important for catalysis
8.4 The Michaelis–Menten Model Accounts for the Kinetic Properties of Many Enzymes
Kinetics is the study of reaction rates
The steady-state assumption facilitates a description of enzyme kinetics
Variations in KM can have physiological consequences
KM and Vmax values can be determined by several means
KM and Vmax values are important enzyme characteristics
kcat/KM is a measure of catalytic efficiency
Most biochemical reactions include multiple substrates
Allosteric enzymes do not obey Michaelis–Menten kinetics
8.5 Enzymes Can Be Inhibited by Specific Molecules
The different types of reversible inhibitors are kinetically distinguishable
Irreversible inhibitors can be used to map the active site
Penicillin irreversibly inactivates a key enzyme in bacterial cell-wall synthesis
Transition-state analogs are potent inhibitors of enzymes
Enzymes have impact outside the laboratory or clinic
8.6 Enzymes Can Be Studied One Molecule at a Time
APPENDIX Enzymes are Classified on the Basis of the Types of Reactions That They Catalyze
APPENDIX Problem-Solving Strategies
APPENDIX Biochemistry in Focus: The effect of temperature rate on enzyme-catalyzed reactions and the coloring of Siamese cats
Chapter 9 Catalytic Strategies
9.1 Proteases Facilitate a Fundamentally Difficult Reaction
Chymotrypsin possesses a highly reactive serine residue
Chymotrypsin action proceeds in two steps linked by a covalently bound intermediate
Serine is part of a catalytic triad that also includes histidine and aspartate
Catalytic triads are found in other hydrolytic enzymes
The catalytic triad has been dissected by site-directed mutagenesis
Cysteine, aspartyl, and metalloproteases are other major classes of peptide-cleaving enzymes
Protease inhibitors are important drugs
9.2 Carbonic Anhydrases Make a Fast Reaction Faster
Carbonic anhydrase contains a bound zinc ion essential for catalytic activity
Catalysis entails zinc activation of a water molecule
A proton shuttle facilitates rapid regeneration of the active form of the enzyme
9.3 Restriction Enzymes Catalyze Highly Specific DNA-Cleavage Reactions
Cleavage is by in-line displacement of 3′-oxygen from phosphorus by magnesium-activated water
Restriction enzymes require magnesium for catalytic activity
The complete catalytic apparatus is assembled only within complexes of cognate DNA molecules, ensuring specificity
Host-cell DNA is protected by the addition of methyl groups to specific bases
Type II restriction enzymes have a catalytic core in common and are probably related by horizontal gene transfer
9.4 Myosins Harness Changes in Enzyme Conformation to Couple ATP Hydrolysis to Mechanical Work
ATP hydrolysis proceeds by the attack of water on the gamma phosphoryl group
Formation of the transition state for ATP hydrolysis is associated with a substantial conformational change
The altered conformation of myosin persists for a substantial period of time
Scientists can watch single molecules of myosin move
Myosins are a family of enzymes containing P-loop structures
APPENDIX Problem-Solving Strategies
Chapter 10 Regulatory Strategies
10.1 Aspartate Transcarbamoylase Is Allosterically Inhibited by the End Product of Its Pathway
Allosterically regulated enzymes do not follow Michaelis–Menten kinetics
ATCase consists of separable catalytic and regulatory subunits
Allosteric interactions in ATCase are mediated by large changes in quaternary structure
Allosteric regulators modulate the T-to-R equilibrium
10.2 Isozymes Provide a Means of Regulation Specific to Distinct Tissues and Developmental Stages
10.3 Covalent Modification Is a Means of Regulating Enzyme Activity
Kinases and phosphatases control the extent of protein phosphorylation
Phosphorylation is a highly effective means of regulating the activities of target proteins
Cyclic AMP activates protein kinase A by altering the quaternary structure
Mutations in protein kinase A can cause Cushing Syndrome
Exercise modifies the phosphorylation of many proteins
10.4 Many Enzymes Are Activated by Specific Proteolytic Cleavage
Chymotrypsinogen is activated by specific cleavage of a single peptide bond
Proteolytic activation of chymotrypsinogen leads to the formation of a substrate-binding site
The generation of trypsin from trypsinogen leads to the activation of other zymogens
Some proteolytic enzymes have specific inhibitors
Serpins can be degraded by a unique enzyme
Blood clotting is accomplished by a cascade of zymogen activations
Prothrombin must bind to Ca2+ to be converted to thrombin
Fibrinogen is converted by thrombin into a fibrin clot
Vitamin K is required for the formation of ©-carboxyglutamate
The clotting process must be precisely regulated
Hemophilia revealed an early step in clotting
APPENDIX Biochemistry in Focus: Phosphoribosylpyrophosphate synthetase-induced gout
APPENDIX Problem-Solving Strategies
Chapter 11 Carbohydrates
11.1 Monosaccharides Are the Simplest Carbohydrates
Many common sugars exist in cyclic forms
Pyranose and furanose rings can assume different conformations
Glucose is a reducing sugar
Monosaccharides are joined to alcohols and amines through glycosidic bonds
Phosphorylated sugars are key intermediates in energy generation and biosyntheses
11.2 Monosaccharides Are Linked to Form Complex Carbohydrates
Sucrose, lactose, and maltose are the common disaccharides
Glycogen and starch are storage forms of glucose
Cellulose, a structural component of plants, is made of chains of glucose
Human milk oligosaccharides protect newborns from infection
11.3 Carbohydrates Can Be Linked to Proteins to Form Glycoproteins
Carbohydrates can be linked to proteins through asparagine (N-linked) or through serine or threonine (O-linked) residues
The glycoprotein erythropoietin is a vital hormone
Glycosylation functions in nutrient sensing
Proteoglycans, composed of polysaccharides and protein, have important structural roles
Proteoglycans are important components of cartilage
Mucins are glycoprotein components of mucus
Chitin can be processed to a molecule with a variety of uses
Protein glycosylation takes place in the lumen of the endoplasmic reticulum and in the Golgi complex
Specific enzymes are responsible for oligosaccharide assembly
Blood groups are based on protein glycosylation patterns
Errors in glycosylation can result in pathological conditions
Oligosaccharides can be “sequenced”
11.4 Lectins Are Specific Carbohydrate-Binding Proteins
Lectins promote interactions between cells and within cells
Lectins are organized into different classes
Influenza virus binds to sialic acid residues
APPENDIX Biochemistry in Focus: α-Glucosidase (maltase) inhibitors can help to maintain blood glucose homeostsis
Chapter 12 Lipids and Cell Membranes
12.1 Fatty Acids Are Key Constituents of Lipids
Fatty acid names are based on their parent hydrocarbons
Fatty acids vary in chain length and degree of unsaturation
12.2 There Are Three Common Types of Membrane Lipids
Phospholipids are the major class of membrane lipids
Membrane lipids can include carbohydrate moieties
Cholesterol is a lipid based on a steroid nucleus
Archaeal membranes are built from ether lipids with branched chains
A membrane lipid is an amphipathic molecule containing a hydrophilic and a hydrophobic moiety
12.3 Phospholipids and Glycolipids Readily Form Bimolecular Sheets in Aqueous Media
Lipid vesicles can be formed from phospholipids
Lipid bilayers are highly impermeable to ions and most polar molecules
12.4 Proteins Carry Out Most Membrane Processes
Proteins associate with the lipid bilayer in a variety of ways
Proteins interact with membranes in a variety of ways
Some proteins associate with membranes through covalently attached hydrophobic groups
Transmembrane helices can be accurately predicted from amino acid sequences
12.5 Lipids and Many Membrane Proteins Diffuse Rapidly in the Plane of the Membrane
The fluid mosaic model allows lateral movement but not rotation through the membrane
Membrane fluidity is controlled by fatty acid composition and cholesterol content
Lipid rafts are highly dynamic complexes formed between cholesterol and specific lipids
All biological membranes are asymmetric
12.6 Eukaryotic Cells Contain Compartments Bounded by Internal Membranes
APPENDIX Biochemistry in Focus: The curious case of cardiolipin
Chapter 13 Membrane Channels and Pumps
13.1 The Transport of Molecules Across a Membrane May Be Active or Passive
Many molecules require protein transporters to cross membranes
Free energy stored in concentration gradients can be quantified
13.2 Two Families of Membrane Proteins Use ATP Hydrolysis to Pump Ions and Molecules Across Membranes
P-type ATPases couple phosphorylation and conformational changes to pump calcium ions across membranes
Digitalis specifically inhibits the Na+–K+ pump by blocking its dephosphorylation
P-type ATPases are evolutionarily conserved and play a wide range of roles
Multidrug resistance highlights a family of membrane pumps with ATP-binding cassette domains
13.3 Lactose Permease Is an Archetype of Secondary Transporters That Use One Concentration Gradient to Power the Formation of Another
13.4 Specific Channels Can Rapidly Transport Ions Across Membranes
Action potentials are mediated by transient changes in Na+ and K+ permeability
Patch-clamp conductance measurements reveal the activities of single channels
The structure of a potassium ion channel is an archetype for many ion-channel structures
The structure of the potassium ion channel reveals the basis of ion specificity
The structure of the potassium ion channel explains its rapid rate of transport
Voltage gating requires substantial conformational changes in specific ion-channel domains
A channel can be inactivated by occlusion of the pore: the ball-and-chain model
The acetylcholine receptor is an archetype for ligand-gated ion channels
Action potentials integrate the activities of several ion channels working in concert
Disruption of ion channels by mutations or chemicals can be potentially life-threatening
13.5 Gap Junctions Allow Ions and Small Molecules to Flow Between Communicating Cells
13.6 Specific Channels Increase the Permeability of Some Membranes to Water
APPENDIX Biochemistry in Focus: Setting the pace is more than funny business
APPENDIX Problem-Solving Strategies
Chapter 14 Signal-Transduction Pathways
14.1  Epinephrine and Angiotensin II Signaling: Heterotrimeric G Proteins Transmit Signals and Reset Themselves
Ligand binding to 7TM receptors leads to the activation of heterotrimeric G proteins
Activated G proteins transmit signals by binding to other proteins
Cyclic AMP stimulates the phosphorylation of many target proteins by activating protein kinase A
G proteins spontaneously reset themselves through GTP hydrolysis
Some 7TM receptors activate the phosphoinositide cascade
Calcium ion is a widely used second messenger
Calcium ion often activates the regulatory protein calmodulin
14.2 Insulin Signaling: Phosphorylation Cascades Are Central to Many Signal-Transduction Processes
The insulin receptor is a dimer that closes around a bound insulin molecule
Insulin binding results in the cross-phosphorylation and activation of the insulin receptor
The activated insulin-receptor kinase initiates a kinase cascade
Insulin signaling is terminated by the action of phosphatases
14.3 EGF Signaling: Signal-Transduction Pathways Are Poised to Respond
EGF binding results in the dimerization of the EGF receptor
The EGF receptor undergoes phosphorylation of its carboxyl-terminal tail
EGF signaling leads to the activation of Ras, a small G protein
Activated Ras initiates a protein kinase cascade
EGF signaling is terminated by protein phosphatases and the intrinsic GTPase activity of Ras
14.4 Many Elements Recur with Variation in Different Signal-Transduction Pathways
14.5 Defects in Signal-Transduction Pathways Can Lead to Cancer and Other Diseases
Monoclonal antibodies can be used to inhibit signal-transduction pathways activated in tumors
Protein kinase inhibitors can be effective anticancer drugs
Cholera and whooping cough are the result of altered G-protein activity
APPENDIX Biochemistry in Focus: Gases get in on the signaling game
Part II TRANSDUCING AND STORING ENERGY
Chapter 15 Metabolism: Basic Concepts and Design
15.1 Metabolism Is Composed of Many Coupled, Interconnecting Reactions
Metabolism consists of energy-yielding and energy-requiring reactions
A thermodynamically unfavorable reaction can be driven by a favorable reaction
15.2 ATP Is the Universal Currency of Free Energy in Biological Systems
ATP hydrolysis is exergonic
ATP hydrolysis drives metabolism by shifting the equilibrium of coupled reactions
The high phosphoryl potential of ATP results from structural differences between ATP and its hydrolysis products
Phosphoryl-transfer potential is an important form of cellular energy transformation
15.3 The Oxidation of Carbon Fuels Is an Important Source of Cellular Energy
Compounds with high phosphoryl-transfer potential can couple carbon oxidation to ATP synthesis
Ion gradients across membranes provide an important form of cellular energy that can be coupled to ATP synthesis
Phosphates play a prominent role in biochemical processes
Energy from foodstuffs is extracted in three stages
15.4 Metabolic Pathways Contain Many Recurring Motifs
Activated carriers exemplify the modular design and economy of metabolism
Many activated carriers are derived from vitamins
Key reactions are reiterated throughout metabolism
Metabolic processes are regulated in three principal ways
Aspects of metabolism may have evolved from an RNA world
APPENDIX Problem-Solving Strategies
Chapter 16 Glycolysis and Gluconeogenesis
16.1 Glycolysis Is an Energy-Conversion Pathway in Many Organisms
The enzymes of glycolysis are associated with one another
Glycolysis can be divided into two parts
Hexokinase traps glucose in the cell and begins glycolysis
Fructose 1,6-bisphosphate is generated from glucose 6-phosphate
The six-carbon sugar is cleaved into two three-carbon fragments
Mechanism: Triose phosphate isomerase salvages a three-carbon fragment
The oxidation of an aldehyde to an acid powers the formation of a compound with high phosphoryl-transfer potential
Mechanism: Phosphorylation is coupled to the oxidation of glyceraldehyde 3-phosphate by a thioester intermediate
ATP is formed by phosphoryl transfer from 1,3-bisphosphoglycerate
Additional ATP is generated with the formation of pyruvate
Two ATP molecules are formed in the conversion of glucose into pyruvate
NAD+ is regenerated from the metabolism of pyruvate
Fermentations provide usable energy in the absence of oxygen
Fructose is converted into glycolytic intermediates by fructokinase
Excessive fructose consumption can lead to pathological conditions
Galactose is converted into glucose 6-phosphate
Many adults are intolerant of milk because they are deficient in lactase
Galactose is highly toxic if the transferase is missing
16.2 The Glycolytic Pathway Is Tightly Controlled
Glycolysis in muscle is regulated to meet the need for ATP
The regulation of glycolysis in the liver illustrates the biochemical versatility of the liver
A family of transporters enables glucose to enter and leave animal cells
Aerobic glycolysis is a property of rapidly growing cells
Cancer and endurance training affect glycolysis in a similar fashion
16.3 Glucose Can Be Synthesized from Noncarbohydrate Precursors
Gluconeogenesis is not a reversal of glycolysis
The conversion of pyruvate into phosphoenolpyruvate begins with the formation of oxaloacetate
Oxaloacetate is shuttled into the cytoplasm and converted into phosphoenolpyruvate
The conversion of fructose 1,6-bisphosphate into fructose 6-phosphate and orthophosphate is an irreversible step
The generation of free glucose is an important control point
Six high-transfer-potential phosphoryl groups are spent in synthesizing glucose from pyruvate
16.4 Gluconeogenesis and Glycolysis Are Reciprocally Regulated
Energy charge determines whether glycolysis or gluconeogenesis will be most active
The balance between glycolysis and gluconeogenesis in the liver is sensitive to blood-glucose concentration
Substrate cycles amplify metabolic signals and produce heat
Lactate and alanine formed by contracting muscle are used by other organs
Glycolysis and gluconeogenesis are evolutionarily intertwined
APPENDIX Biochemistry in Focus: Triose phosphate isomerase deficiency (TPID)
APPENDIX Biochemistry in Focus: Pyruvate carboxylase deficiency (PCD)
APPENDIX Problem-Solving Strategies
Chapter 17 The Citric Acid Cycle
17.1 The Pyruvate Dehydrogenase Complex Links Glycolysis to the Citric Acid Cycle
Mechanism: The synthesis of acetyl coenzyme A from pyruvate requires three enzymes and five coenzymes
Flexible linkages allow lipoamide to move between different active sites
17.2 The Citric Acid Cycle Oxidizes Two-Carbon Units
Citrate synthase forms citrate from oxaloacetate and acetyl coenzyme A
Mechanism: The mechanism of citrate synthase prevents undesirable reactions
Citrate is isomerized into isocitrate
Isocitrate is oxidized and decarboxylated to alpha-ketoglutarate
Succinyl coenzyme A is formed by the oxidative decarboxylation of alpha-ketoglutarate
A compound with high phosphoryl-transfer potential is generated from succinyl coenzyme A
Mechanism: Succinyl coenzyme A synthetase transforms types of biochemical energy
Oxaloacetate is regenerated by the oxidation of succinate
The citric acid cycle produces high-transfer-potential electrons, ATP, and CO2
17.3 Entry to the Citric Acid Cycle and Metabolism Through It Are Controlled
The pyruvate dehydrogenase complex is regulated allosterically and by reversible phosphorylation
The citric acid cycle is controlled at several points
Defects in the citric acid cycle contribute to the development of cancer
An enzyme in lipid metabolism is hijacked to inhibit pyruvate dehydrogenase activity
17.4 The Citric Acid Cycle Is a Source of Biosynthetic Precursors
The citric acid cycle must be capable of being rapidly replenished
The disruption of pyruvate metabolism is the cause of beriberi and poisoning by mercury and arsenic
The citric acid cycle may have evolved from preexisting pathways
17.5 The Glyoxylate Cycle Enables Plants and Bacteria to Grow on Acetate
APPENDIX Biochemistry in Focus: New treatments for tuberculosis may be on the horizon
APPENDIX Problem-Solving Strategies
Chapter 18 Oxidative Phosphorylation
18.1 Eukaryotic Oxidative Phosphorylation Takes Place in Mitochondria
Mitochondria are bounded by a double membrane
Mitochondria are the result of an endosymbiotic event
18.2 Oxidative Phosphorylation Depends on Electron Transfer
The electron-transfer potential of an electron is measured as redox potential
Electron flow from NADH to molecular oxygen powers the formation of a proton gradient
18.3 The Respiratory Chain Consists of Four Complexes: Three Proton Pumps and a Physical Link to the Citric Acid Cycle
Iron–sulfur clusters are common components of the electron-transport chain
The high-potential electrons of NADH enter the respiratory chain at NADH-Q oxidoreductase
Ubiquinol is the entry point for electrons from FADH2 of flavoproteins
Electrons flow from ubiquinol to cytochrome c through Q-cytochrome c oxidoreductase
The Q cycle funnels electrons from a two-electron carrier to a one-electron carrier and pumps protons
Cytochrome c oxidase catalyzes the reduction of molecular oxygen to water
Much of the electron-transport chain is organized into a complex called the respirasome
Toxic derivatives of molecular oxygen such as superoxide radicals are scavenged by protective enzymes
Electrons can be transferred between groups that are not in contact
The conformation of cytochrome c has remained essentially constant for more than a billion years
18.4 A Proton Gradient Powers the Synthesis of ATP
ATP synthase is composed of a proton-conducting unit and a catalytic unit
Proton flow through ATP synthase leads to the release of tightly bound ATP: The binding-change mechanism
Rotational catalysis is the world’s smallest molecular motor
Proton flow around the c ring powers ATP synthesis
ATP synthase and G proteins have several common features
18.5 Many Shuttles Allow Movement Across Mitochondrial Membranes
Electrons from cytoplasmic NADH enter mitochondria by shuttles
The entry of ADP into mitochondria is coupled to the exit of ATP by ATP-ADP translocase
Mitochondrial transporters for metabolites have a common tripartite structure
18.6 The Regulation of Cellular Respiration Is Governed Primarily by the Need for ATP
The complete oxidation of glucose yields about 30 molecules of ATP
The rate of oxidative phosphorylation is determined by the need for ATP
ATP synthase can be regulated
Regulated uncoupling leads to the generation of heat
Reintroduction of UCP-1 into pigs may be economically valuable
Oxidative phosphorylation can be inhibited at many stages
Mitochondrial diseases are being discovered
Mitochondria play a key role in apoptosis
Power transmission by proton gradients is a central motif of bioenergetics
APPENDIX Biochemistry in Focus: Leber hereditary optic neuropathy can result from defects in Complex I
Chapter 19 The Light Reactions of Photosynthesis
19.1 Photosynthesis Takes Place in Chloroplasts
The primary events of photosynthesis take place in thylakoid membranes
Chloroplasts arose from an endosymbiotic event
19.2 Light Absorption by Chlorophyll Induces Electron Transfer
A special pair of chlorophylls initiate charge separation
Cyclic electron flow reduces the cytochrome of the reaction center
19.3 Two Photosystems Generate a Proton Gradient and NADPH in Oxygenic Photosynthesis
Photosystem II transfers electrons from water to plastoquinone and generates a proton gradient
Cytochrome bf links photosystem II to photosystem I
Photosystem I uses light energy to generate reduced ferredoxin, a powerful reductant
Ferredoxin–NADP+ reductase converts NADP+ into NADPH
19.4 A Proton Gradient across the Thylakoid Membrane Drives ATP Synthesis
The ATP synthase of chloroplasts closely resembles those of mitochondria and prokaryotes
The activity of chloroplast ATP synthase is regulated
Cyclic electron flow through photosystem I leads to the production of ATP instead of NADPH
The absorption of eight photons yields one O2, two NADPH, and three ATP molecules
19.5 Accessory Pigments Funnel Energy into Reaction Centers
Resonance energy transfer allows energy to move from the site of initial absorbance to the reaction center
The components of photosynthesis are highly organized
Many herbicides inhibit the light reactions of photosynthesis
19.6 The Ability to Convert Light into Chemical Energy Is Ancient
Artificial photosynthetic systems may provide clean, renewable energy
APPENDIX Biochemistry in Focus: Increasing the efficiency of photosynthesis will increase crop yields
APPENDIX Problem-Solving Strategies
Chapter 20 The Calvin Cycle and the Pentose Phosphate Pathway
20.1 The Calvin Cycle Synthesizes Hexoses from Carbon Dioxide and Water
Carbon dioxide reacts with ribulose 1,5-bisphosphate to form two molecules of 3-phosphoglycerate
Rubisco activity depends on magnesium and carbamate
Rubisco activase is essential for rubisco activity
Rubisco also catalyzes a wasteful oxygenase reaction: Catalytic imperfection
Hexose phosphates are made from phosphoglycerate, and ribulose 1,5-bisphosphate is regenerated
Three ATP and two NADPH molecules are used to bring carbon dioxide to the level of a hexose
Starch and sucrose are the major carbohydrate stores in plants
20.2 The Activity of the Calvin Cycle Depends on Environmental Conditions
Rubisco is activated by light-driven changes in proton and magnesium ion concentrations
Thioredoxin plays a key role in regulating the Calvin cycle
The C4 pathway of tropical plants accelerates photosynthesis by concentrating carbon dioxide
Crassulacean acid metabolism permits growth in arid ecosystems
20.3 The Pentose Phosphate Pathway Generates NADPH and Synthesizes Five-Carbon Sugars
Two molecules of NADPH are generated in the conversion of glucose 6-phosphate into ribulose 5-phosphate
The pentose phosphate pathway and glycolysis are linked by transketolase and transaldolase
Mechanism: Transketolase and transaldolase stabilize carbanionic intermediates by different mechanisms
20.4 The Metabolism of Glucose 6-Phosphate by the Pentose Phosphate Pathway Is Coordinated with Glycolysis
The rate of the oxidative phase of the pentose phosphate pathway is controlled by the level of NADP+
The flow of glucose 6-phosphate depends on the need for NADPH, ribose 5-phosphate, and ATP
The pentose phosphate pathway is required for rapid cell growth
Through the looking-glass: The Calvin cycle and the pentose phosphate pathway are mirror images
20.5 Glucose 6-Phosphate Dehydrogenase Plays a Key Role in Protection Against Reactive Oxygen Species
Glucose 6-phosphate dehydrogenase deficiency causes a drug-induced hemolytic anemia
A deficiency of glucose 6-phosphate dehydrogenase confers an evolutionary advantage in some circumstances
APPENDIX Biochemistry in Focus
APPENDIX Biochemistry in Focus: Hummingbirds and the pentose phosphate pathway
APPENDIX Problem-Solving Strategies
Chapter 21 Glycogen Metabolism
21.1 Glycogen Breakdown Requires the Interplay of Several Enzymes
Phosphorylase catalyzes the phosphorolytic cleavage of glycogen to release glucose 1-phosphate
Mechanism: Pyridoxal phosphate participates in the phosphorolytic cleavage of glycogen
A debranching enzyme also is needed for the breakdown of glycogen
Phosphoglucomutase converts glucose 1-phosphate into glucose 6-phosphate
The liver contains glucose 6-phosphatase, a hydrolytic enzyme absent from muscle
21.2 Phosphorylase Is Regulated by Allosteric Interactions and Reversible Phosphorylation
Liver phosphorylase produces glucose for use by other tissues
Muscle phosphorylase is regulated by the intracellular energy charge
Biochemical characteristics of muscle fiber types differ
Phosphorylation promotes the conversion of phosphorylase b to phosphorylase a
Phosphorylase kinase is activated by phosphorylation and calcium ions
An isomeric form of glycogen phosphorylase exists in the brain
21.3 Epinephrine and Glucagon Signal the Need for Glycogen Breakdown
G proteins transmit the signal for the initiation of glycogen breakdown
Glycogen breakdown must be rapidly turned off when necessary
The regulation of glycogen phosphorylase became more sophisticated as the enzyme evolved
21.4 Glycogen Is Synthesized and Degraded by Different Pathways
UDP-glucose is an activated form of glucose
Glycogen synthase catalyzes the transfer of glucose from UDP-glucose to a growing chain
A branching enzyme forms 〈-1,6 linkages
Glycogen synthase is the key regulatory enzyme in glycogen synthesis
Glycogen is an efficient storage form of glucose
21.5 Glycogen Breakdown and Synthesis Are Reciprocally Regulated
Protein phosphatase 1 reverses the regulatory effects of kinases on glycogen metabolism
Insulin stimulates glycogen synthesis by inactivating glycogen synthase kinase
Glycogen metabolism in the liver regulates the blood-glucose concentration
A biochemical understanding of glycogen-storage diseases is possible
APPENDIX Biochemistry in Focus: McArdle disease results from a lack of skeletal muscle glycogen phosphorylase
APPENDIX Problem-Solving Strategies
Chapter 22 Fatty Acid Metabolism
22.1 Triacylglycerols Are Highly Concentrated Energy Stores
Dietary lipids are digested by pancreatic lipases
Dietary lipids are transported in chylomicrons
22.2 The Use of Fatty Acids as Fuel Requires Three Stages of Processing
Triacylglycerols are hydrolyzed by hormone-stimulated lipases
Free fatty acids and glycerol are released into the blood
Fatty acids are linked to coenzyme A before they are oxidized
Carnitine carries long-chain activated fatty acids into the mitochondrial matrix
Acetyl CoA, NADH, and FADH2 are generated in each round of fatty acid oxidation
The complete oxidation of palmitate yields 106 molecules of ATP
22.3 Unsaturated and Odd-Chain Fatty Acids Require Additional Steps for Degradation
An isomerase and a reductase are required for the oxidation of unsaturated fatty acids
Odd-chain fatty acids yield propionyl CoA in the final thiolysis step
Vitamin B12 contains a corrin ring and a cobalt atom
Mechanism: Methylmalonyl CoA mutase catalyzes a rearrangement to form succinyl CoA
Fatty acids are also oxidized in peroxisomes
Some fatty acids may contribute to the development of pathological conditions
22.4 Ketone Bodies Are a Fuel Source Derived from Fats
Ketone bodies are a major fuel in some tissues
Animals cannot convert fatty acids into glucose
22.5 Fatty Acids Are Synthesized by Fatty Acid Synthase
Fatty acids are synthesized and degraded by different pathways
The formation of malonyl CoA is the committed step in fatty acid synthesis
Intermediates in fatty acid synthesis are attached to an acyl carrier protein
Fatty acid synthesis consists of a series of condensation, reduction, dehydration, and reduction reactions
Fatty acids are synthesized by a multifunctional enzyme complex in animals
The synthesis of palmitate requires 8 molecules of acetyl CoA, 14 molecules of NADPH, and 7 molecules of ATP
Citrate carries acetyl groups from mitochondria to the cytoplasm for fatty acid synthesis
Several sources supply NADPH for fatty acid synthesis
Fatty acid metabolism is altered in tumor cells
Triacylglycerols may become an important renewable energy source
22.6 The Elongation and Unsaturation of Fatty Acids are Accomplished by Accessory Enzyme Systems
Membrane-bound enzymes generate unsaturated fatty acids
Eicosanoid hormones are derived from polyunsaturated fatty acids
Variations on a theme: Polyketide and nonribosomal peptide synthetases resemble fatty acid synthase
22.7 Acetyl CoA Carboxylase Plays a Key Role in Controlling Fatty Acid Metabolism
Acetyl CoA carboxylase is regulated by conditions in the cell
Acetyl CoA carboxylase is regulated by a variety of hormones
AMP-activated protein kinase is a key regulator of metabolism
APPENDIX Biochemistry in Focus: Ethanol consumption results in triacylglycerol accumulation in the liver
APPENDIX Problem-Solving Strategies
Chapter 23 Protein Turnover and Amino Acid Catabolism
23.1 Proteins are Degraded to Amino Acids
The digestion of dietary proteins begins in the stomach and is completed in the intestine
Cellular proteins are degraded at different rates
23.2 Protein Turnover Is Tightly Regulated
Ubiquitin tags proteins for destruction
The proteasome digests the ubiquitin-tagged proteins
The ubiquitin pathway and the proteasome have prokaryotic counterparts
Protein degradation can be used to regulate biological function
23.3 The First Step in Amino Acid Degradation Is the Removal of Nitrogen
Alpha-amino groups are converted into ammonium ions by the oxidative deamination of glutamate
Mechanism: Pyridoxal phosphate forms Schiff-base intermediates in aminotransferases
Aspartate aminotransferase is an archetypal pyridoxal-dependent transaminase
Blood levels of aminotransferases serve a diagnostic function
Pyridoxal phosphate enzymes catalyze a wide array of reactions
Serine and threonine can be directly deaminated
Peripheral tissues transport nitrogen to the liver
23.4 Ammonium Ion Is Converted into Urea in Most Terrestrial Vertebrates
The urea cycle begins with the formation of carbamoyl phosphate
Carbamoyl phosphate synthetase is the key regulatory enzyme for urea synthesis
Carbamoyl phosphate reacts with ornithine to begin the urea cycle
The urea cycle is linked to gluconeogenesis
Urea-cycle enzymes are evolutionarily related to enzymes in other metabolic pathways
Inherited defects of the urea cycle cause hyperammonemia and can lead to brain damage
Urea is not the only means of disposing of excess nitrogen
23.5 Carbon Atoms of Degraded Amino Acids Emerge as Major Metabolic Intermediates
Pyruvate is an entry point into metabolism for a number of amino acids
Oxaloacetate is an entry point into metabolism for aspartate and asparagine
Alpha-ketoglutarate is an entry point into metabolism for five-carbon amino acids
Succinyl coenzyme A is a point of entry for several amino acids
Methionine degradation requires the formation of a key methyl donor, S-adenosylmethionine
Threonine deaminase initiates the degradation of threonine
The branched-chain amino acids yield acetyl CoA, acetoacetate, or propionyl CoA
Oxygenases are required for the degradation of aromatic amino acids
Protein metabolism helps to power the flight of migratory birds
23.6 Inborn Errors of Metabolism Can Disrupt Amino Acid Degradation
Phenylketonuria is one of the most common metabolic disorders
Determining the basis of the neurological symptoms of phenylketonuria is an active area of research
APPENDIX Biochemistry in Focus: Methylmalonic acidemia results from an inborn error of metabolism
APPENDIX Problem-Solving Strategies
Part III SYNTHESIZING THE MOLECULES OF LIFE
Chapter 24 The Biosynthesis of Amino Acids
24.1 Nitrogen Fixation: Microorganisms Use ATP and a Powerful Reductant to Reduce Atmospheric Nitrogen to Ammonia
The iron–molybdenum cofactor of nitrogenase binds and reduces atmospheric nitrogen
Ammonium ion is assimilated into an amino acid through glutamate and glutamine
24.2 Amino Acids Are Made from Intermediates of the Citric Acid Cycle and Other Major Pathways
Human beings can synthesize some amino acids but must obtain others from their diet
Aspartate, alanine, and glutamate are formed by the addition of an amino group to an alpha-ketoacid
A common step determines the chirality of all amino acids
The formation of asparagine from aspartate requires an adenylated intermediate
Glutamate is the precursor of glutamine, proline, and arginine
3-Phosphoglycerate is the precursor of serine, cysteine, and glycine
Tetrahydrofolate carries activated one-carbon units at several oxidation levels
S-Adenosylmethionine is the major donor of methyl groups
Cysteine is synthesized from serine and homocysteine
High homocysteine levels correlate with vascular disease
Shikimate and chorismate are intermediates in the biosynthesis of aromatic amino acids
Tryptophan synthase illustrates substrate channeling in enzymatic catalysis
24.3 Feedback Inhibition Regulates Amino Acid Biosynthesis
Branched pathways require sophisticated regulation
The sensitivity of glutamine synthetase to allosteric regulation is altered by covalent modification
24.4 Amino Acids Are Precursors of Many Biomolecules
Glutathione, a gamma-glutamyl peptide, serves as a sulfhydryl buffer and an antioxidant
Nitric oxide, a short-lived signal molecule, is formed from arginine
Amino acids are precursors for a number of neurotransmitters
Porphyrins are synthesized from glycine and succinyl coenzyme A
Porphyrins accumulate in some inherited disorders of porphyrin metabolism
APPENDIX Biochemistry in Focus: Tyrosine is a precursor for human pigments
APPENDIX Problem-Solving Strategies
Chapter 25 Nucleotide Biosynthesis
25.1 The Pyrimidine Ring Is Assembled de Novo or Recovered by Salvage Pathways
Bicarbonate and other oxygenated carbon compounds are activated by phosphorylation
The side chain of glutamine can be hydrolyzed to generate ammonia
Intermediates can move between active sites by channeling
Orotate acquires a ribose ring from PRPP to form a pyrimidine nucleotide and is converted into uridylate
Nucleotide mono-, di-, and triphosphates are interconvertible
CTP is formed by amination of UTP
Salvage pathways recycle pyrimidine bases
25.2 Purine Bases Can Be Synthesized de Novo or Recycled by Salvage Pathways
The purine ring system is assembled on ribose phosphate
The purine ring is assembled by successive steps of activation by phosphorylation followed by displacement
AMP and GMP are formed from IMP
Enzymes of the purine synthesis pathway associate with one another in vivo
Salvage pathways economize intracellular energy expenditure
25.3 Deoxyribonucleotides Are Synthesized by the Reduction of Ribonucleotides Through a Radical Mechanism
Mechanism: A tyrosyl radical is critical to the action of ribonucleotide reductase
Stable radicals other than tyrosyl radical are employed by other ribonucleotide reductases
Thymidylate is formed by the methylation of deoxyuridylate
Dihydrofolate reductase catalyzes the regeneration of tetrahydrofolate, a one-carbon carrier
Several valuable anticancer drugs block the synthesis of thymidylate
25.4 Key Steps in Nucleotide Biosynthesis Are Regulated by Feedback Inhibition
Pyrimidine biosynthesis is regulated by aspartate transcarbamoylase
The synthesis of purine nucleotides is controlled by feedback inhibition at several sites
The synthesis of deoxyribonucleotides is controlled by the regulation of ribonucleotide reductase
25.5 Disruptions in Nucleotide Metabolism Can Cause Pathological Conditions
The loss of adenosine deaminase activity results in severe combined immunodeficiency
Gout is induced by high serum levels of urate
Lesch–Nyhan syndrome is a dramatic consequence of mutations in a salvage-pathway enzyme
Folic acid deficiency promotes birth defects such as spina bifida
APPENDIX Biochemistry in Focus: Uridine plays a role in caloric homeostasis
APPENDIX Problem-Solving Strategies
Chapter 26 The Biosynthesis of Membrane Lipids and Steroids
26.1 Phosphatidate Is a Common Intermediate in the Synthesis of Phospholipids and Triacylglycerols
The synthesis of phospholipids requires an activated intermediate
Some phospholipids are synthesized from an activated alcohol
Phosphatidylcholine is an abundant phospholipid
Excess choline is implicated in the development of heart disease
Base-exchange reactions can generate phospholipids
Sphingolipids are synthesized from ceramide
Gangliosides are carbohydrate-rich sphingolipids that contain acidic sugars
Sphingolipids confer diversity on lipid structure and function
Respiratory distress syndrome and Tay–Sachs disease result from the disruption of lipid metabolism
Ceramide metabolism stimulates tumor growth
Phosphatidic acid phosphatase is a key regulatory enzyme in lipid metabolism
26.2 Cholesterol Is Synthesized from Acetyl Coenzyme A in Three Stages
The synthesis of mevalonate, which is activated as isopentenyl pyrophosphate, initiates the synthesis of cholesterol
Squalene (C30) is synthesized from six molecules of isopentenyl pyrophosphate (C5)
Squalene cyclizes to form cholesterol
26.3 The Complex Regulation of Cholesterol Biosynthesis Takes Place at Several Levels
Lipoproteins transport cholesterol and triacylglycerols throughout the organism
Low-density lipoproteins play a central role in cholesterol metabolism
The absence of the LDL receptor leads to hypercholesterolemia and atherosclerosis
Mutations in the LDL receptor prevent LDL release and result in receptor destruction
Inability to transport cholesterol from the lysosome causes Niemann-Pick disease
Cycling of the LDL receptor is regulated
HDL appears to protect against atherosclerosis
The clinical management of cholesterol levels can be understood at a biochemical level
26.4 Important Biochemicals Are Synthesized from Cholesterol and Isoprene
Letters identify the steroid rings and numbers identify the carbon atoms
Steroids are hydroxylated by cytochrome P450 monooxygenases that use NADPH and O2
The cytochrome P450 system is widespread and performs a protective function
Pregnenolone, a precursor of many other steroids, is formed from cholesterol by cleavage of its side chain
Progesterone and corticosteroids are synthesized from pregnenolone
Androgens and estrogens are synthesized from pregnenolone
Vitamin D is derived from cholesterol by the ring- splitting activity of light
Five-carbon units are joined to form a wide variety of biomolecules
Some isoprenoids have industrial applications
APPENDIX Biochemistry in Focus: Excess ceramides may cause insulin insensitivity
APPENDIX Problem-Solving Strategies
Chapter 27 The Integration of Metabolism
27.1 Caloric Homeostasis Is a Means of Regulating Body Weight
27.2 The Brain Plays a Key Role in Caloric Homeostasis
Signals from the gastrointestinal tract induce feelings of satiety
Leptin and insulin regulate long-term control over caloric homeostasis
Leptin is one of several hormones secreted by adipose tissue
Leptin resistance may be a contributing factor to obesity
Dieting is used to combat obesity
27.3 Diabetes Is a Common Metabolic Disease Often Resulting from Obesity
Insulin initiates a complex signal-transduction pathway in muscle
Metabolic syndrome often precedes type 2 diabetes
Excess fatty acids in muscle modify metabolism
Insulin resistance in muscle facilitates pancreatic failure
Metabolic derangements in type 1 diabetes result from insulin insufficiency and glucagon excess
27.4 Exercise Beneficially Alters the Biochemistry of Cells
Mitochondrial biogenesis is stimulated by muscular activity
Fuel choice during exercise is determined by the intensity and duration of activity
27.5 Food Intake and Starvation Induce Metabolic Changes
The starved–fed cycle is the physiological response to a fast
Metabolic adaptations in prolonged starvation minimize protein degradation
27.6 Ethanol Alters Energy Metabolism in the Liver
Ethanol metabolism leads to an excess of NADH
Excess ethanol consumption disrupts vitamin metabolism
APPENDIX Biochemistry in Focus: Adipokines help to regulate metabolism in the liver
APPENDIX Biochemistry in Focus: Exercise alters muscle and whole-body metabolism
APPENDIX Problem-Solving Strategies
Chapter 28 Drug Development
28.1 Compounds Must Meet Stringent Criteria to be Developed Into Drugs
Drug must be potent and selective
Drugs must have suitable properties to reach their targets
Toxicity can limit drug effectiveness
28.2 Drug Candidates Can Be Discovered by Serendipity, Screening, or Design
Serendipitous observations can drive drug development
Natural products are a valuable source of drugs and drug leads
Screening libraries of synthetic compounds expands the opportunity for identification of drug leads
Drugs can be designed on the basis of three-dimensional structural information about their targets
28.3 Genomic Analyses Can Aid Drug Discovery
Potential targets can be identified in the human proteome
Animal models can be developed to test the validity of potential drug targets
Potential targets can be identified in the genomes of pathogens
Genetic differences influence individual responses to drugs
28.4 The Clinical Development of Drugs Proceeds Through Several Phases
Clinical trials are time consuming and expensive
The evolution of drug resistance can limit the utility of drugs for infectious agents and cancer
APPENDIX Biochemistry in Focus: Monoclonal antibodies: Expanding the drug developer’s toolbox
Chapter 29 DNA Replication, Repair, and Recombination
29.1 DNA Replication Proceeds by the Polymerization of Deoxyribonucleoside Triphosphates Along a Template
DNA polymerases require a template and a primer
All DNA polymerases have structural features in common
Two bound metal ions participate in the polymerase reaction
The specificity of replication is dictated by complementarity of shape between bases
An RNA primer synthesized by primase enables DNA synthesis to begin
One strand of DNA is made continuously, whereas the other strand is synthesized in fragments
DNA ligase joins ends of DNA in duplex regions
The separation of DNA strands requires specific helicases and ATP hydrolysis
29.2 DNA Unwinding and Supercoiling Are Controlled by Topoisomerases
The linking number of DNA, a topological property, determines the degree of supercoiling
Topoisomerases prepare the double helix for unwinding
Type I topoisomerases relax supercoiled structures
Type II topoisomerases can introduce negative supercoils through coupling to ATP hydrolysis
29.3 DNA Replication Is Highly Coordinated
DNA replication requires highly processive polymerases
The leading and lagging strands are synthesized in a coordinated fashion
DNA replication in Escherichia coli begins at a unique site and proceeds through initiation, elongation, and termination
DNA synthesis in eukaryotes is initiated at multiple sites
Telomeres are unique structures at the ends of linear chromosomes
Telomeres are replicated by telomerase, a specialized polymerase that carries its own RNA template
29.4 Many Types of DNA Damage Can Be Repaired
Errors can arise in DNA replication
Bases can be damaged by oxidizing agents, alkylating agents, and light
DNA damage can be detected and repaired by a variety of systems
The presence of thymine instead of uracil in DNA permits the repair of deaminated cytosine
Some genetic diseases are caused by the expansion of repeats of three nucleotides
Many cancers are caused by the defective repair of DNA
Many potential carcinogens can be detected by their mutagenic action on bacteria
29.5 DNA Recombination Plays Important Roles in Replication, Repair, and Other Processes
RecA can initiate recombination by promoting strand invasion
Some recombination reactions proceed through Holliday-junction intermediates
APPENDIX Biochemistry in Focus: Identifying amino acids crucial for DNA replication fidelity
Chapter 30 RNA Synthesis and Processing
30.1 RNA Polymerases Catalyze Transcription
RNA chains are formed de novo and grow in the 5′-to-3′ direction
RNA polymerases backtrack and correct errors
RNA polymerase binds to promoter sites on the DNA template to initiate transcription
Sigma subunits of RNA polymerase recognize promoter sites
RNA polymerases must unwind the template double helix for transcription to take place
Elongation takes place at transcription bubbles that move along the DNA template
Sequences within the newly transcribed RNA signal termination
Some messenger RNAs directly sense metabolite concentrations
The rho protein helps to terminate the transcription of some genes
Some antibiotics inhibit transcription
Precursors of transfer and ribosomal RNA are cleaved and chemically modified after transcription in prokaryotes
30.2 Transcription in Eukaryotes Is Highly Regulated
Three types of RNA polymerase synthesize RNA in eukaryotic cells
Three common elements can be found in the RNA polymerase II promoter region
The TFIID protein complex initiates the assembly of the active transcription complex
Multiple transcription factors interact with eukaryotic promoters
Enhancer sequences can stimulate transcription at start sites thousands of bases away
30.3 The Transcription Products of Eukaryotic Polymerases Are Processed
RNA polymerase I produces three ribosomal RNAs
RNA polymerase III produces transfer RNA
The product of RNA polymerase II, the pre-mRNA transcript, acquires a 5′ cap and a 3′ poly(A) tail
Small regulatory RNAs are cleaved from larger precursors
RNA editing changes the proteins encoded by mRNA
Sequences at the ends of introns specify splice sites in mRNA precursors
Splicing consists of two sequential transesterification reactions
Small nuclear RNAs in spliceosomes catalyze the splicing of mRNA precursors
Transcription and processing of mRNA are coupled
Mutations that affect pre-mRNA splicing cause disease
Most human pre-mRNAs can be spliced in alternative ways to yield different proteins
30.4 The Discovery of Catalytic RNA was Revealing in Regard to Both Mechanism and Evolution
APPENDIX Biochemistry in Focus: Discovering enzymes made of RNA
Chapter 31 Protein Synthesis
31.1 Protein Synthesis Requires the Translation of Nucleotide Sequences into Amino Acid Sequences
The synthesis of long proteins requires a low error frequency
Transfer RNA molecules have a common design
Some transfer RNA molecules recognize more than one codon because of wobble in base-pairing
31.2 Aminoacyl Transfer RNA Synthetases Read the Genetic Code
Amino acids are first activated by adenylation
Aminoacyl-tRNA synthetases have highly discriminating amino acid activation sites
Proofreading by aminoacyl-tRNA synthetases increases the fidelity of protein synthesis
Synthetases recognize various features of transfer RNA molecules
Aminoacyl-tRNA synthetases can be divided into two classes
31.3 The Ribosome Is the Site of Protein Synthesis
Ribosomal RNAs (5S, 16S, and 23S rRNA) play a central role in protein synthesis
Ribosomes have three tRNA-binding sites that bridge the 30S and 50S subunits
The start signal is usually AUG preceded by several bases that pair with 16S rRNA
Bacterial protein synthesis is initiated by formylmethionyl transfer RNA
Formylmethionyl-tRNAf is placed in the P site of the ribosome in the formation of the 70S initiation complex
Elongation factors deliver aminoacyl-tRNA to the ribosome
Peptidyl transferase catalyzes peptide-bond synthesis
The formation of a peptide bond is followed by the GTP-driven translocation of tRNAs and mRNA
Protein synthesis is terminated by release factors that read stop codons
31.4 Eukaryotic Protein Synthesis Differs from Bacterial Protein Synthesis Primarily in Translation Initiation
Mutations in initiation factor 2 cause a curious pathological condition
31.5 A Variety of Antibiotics and Toxins Can Inhibit Protein Synthesis
Some antibiotics inhibit protein synthesis
Diphtheria toxin blocks protein synthesis in eukaryotes by inhibiting translocation
Some toxins modify 28S ribosomal RNA
31.6 Ribosomes Bound to the Endoplasmic Reticulum Manufacture Secretory and Membrane Proteins
Protein synthesis begins on ribosomes that are free in the cytoplasm
Signal sequences mark proteins for translocation across the endoplasmic reticulum membrane
Transport vesicles carry cargo proteins to their final destination
APPENDIX Biochemistry in Focus: Selective control of gene expression by ribosomes
APPENDIX Problem-Solving Strategies
Chapter 32 The Control of Gene Expression in Prokaryotes
32.1 Many DNA-Binding Proteins Recognize Specific DNA Sequences
The helix-turn-helix motif is common to many prokaryotic DNA-binding proteins
32.2 Prokaryotic DNA-Binding Proteins Bind Specifically to Regulatory Sites in Operons
An operon consists of regulatory elements and protein-encoding genes
The lac repressor protein in the absence of lactose binds to the operator and blocks transcription
Ligand binding can induce structural changes in regulatory proteins
The operon is a common regulatory unit in prokaryotes
Transcription can be stimulated by proteins that contact RNA polymerase
32.3 Regulatory Circuits Can Result in Switching Between Patterns of Gene Expression
The ⎣ repressor regulates its own expression
A circuit based on the ⎣ repressor and Cro forms a genetic switch
Many prokaryotic cells release chemical signals that regulate gene expression in other cells
Biofilms are complex communities of prokaryotes
32.4 Gene Expression Can Be Controlled at Posttranscriptional Levels
Attenuation is a prokaryotic mechanism for regulating transcription through the modulation of nascent RNA secondary structure
APPENDIX Biochemistry in Focus: Regulating gene expression through proteolysis
Chapter 33 The Control of Gene Expression in Eukaryotes
33.1 Eukaryotic DNA Is Organized into Chromatin
Nucleosomes are complexes of DNA and histones
DNA wraps around histone octamers to form nucleosomes
33.2 Transcription Factors Bind DNA and Regulate Transcription Initiation
A range of DNA-binding structures are employed by eukaryotic DNA-binding proteins
Activation domains interact with other proteins
Multiple transcription factors interact with eukaryotic regulatory regions
Enhancers can stimulate transcription in specific cell types
Induced pluripotent stem cells can be generated by introducing four transcription factors into differentiated cells
33.3 The Control of Gene Expression Can Require Chromatin Remodeling
The methylation of DNA can alter patterns of gene expression
Steroids and related hydrophobic molecules pass through membranes and bind to DNA-binding receptors
Nuclear hormone receptors regulate transcription by recruiting coactivators to the transcription complex
Steroid-hormone receptors are targets for drugs
Chromatin structure is modulated through covalent modifications of histone tails
Transcriptional repression can be achieved through histone deacetylation and other modifications
33.4 Eukaryotic Gene Expression Can Be Controlled at Posttranscriptional Levels
Genes associated with iron metabolism are translationally regulated in animals
Small RNAs regulate the expression of many eukaryotic genes
APPENDIX Biochemistry in Focus: A mechanism for consolidating epigenetic modifications
Part IV RESPONDING TO ENVIRONMENTAL CHANGES (Online Only)
Chapter 34 Sensory Systems (Online Only)
34.1 A Wide Variety of Organic Compounds Are Detected by Olfaction
Olfaction is mediated by an enormous family of seven-transmembrane-helix receptors
Odorants are decoded by a combinatorial mechanism
34.2 Taste Is a Combination of Senses That Function by Different Mechanisms
Sequencing of the human genome led to the discovery of a large family of 7TM bitter receptors
A heterodimeric 7TM receptor responds to sweet compounds
Umami, the taste of glutamate and aspartate, is mediated by a heterodimeric receptor related to the sweet receptor
Salty tastes are detected primarily by the passage of sodium ions through channels
Sour tastes arise from the effects of hydrogen ions (acids) on channels
34.3 Photoreceptor Molecules in the Eye Detect Visible Light
Rhodopsin, a specialized 7TM receptor, absorbs visible light
Light absorption induces a specific isomerization of bound 11-cis-retinal
Light-induced lowering of the calcium level coordinates recovery
Color vision is mediated by three cone receptors that are homologs of rhodopsin
Rearrangements in the genes for the green and red pigments lead to “color blindness”
34.4 Hearing Depends on the Speedy Detection of Mechanical Stimuli
Hair cells use a connected bundle of stereocilia to detect tiny motions
Mechanosensory channels have been identified in Drosophila and vertebrates
34.5 Touch Includes the Sensing of Pressure, Temperature, and Other Factors
Studies of capsaicin reveal a receptor for sensing high temperatures and other painful stimuli
APPENDIX Biochemistry in Focus: Binding many palatable tastants with a single receptor
Chapter 35 The Immune System (Online Only)
35.1 Antibodies Possess Distinct Antigen-Binding and Effector Units
35.2 Antibodies Bind Specific Molecules Through Hypervariable Loops
The immunoglobulin fold consists of a beta-sandwich framework with hypervariable loops
X-ray analyses have revealed how antibodies bind antigens
Large antigens bind antibodies with numerous interactions
35.3 Diversity Is Generated by Gene Rearrangements
J (joining) genes and D (diversity) genes increase antibody diversity
More than 108 antibodies can be formed by combinatorial association and somatic mutation
The oligomerization of antibodies expressed on the surfaces of immature B cells triggers antibody secretion
Different classes of antibodies are formed by the hopping of VH genes
35.4 Major-Histocompatibility-Complex Proteins Present Peptide Antigens on Cell Surfaces for Recognition by T-Cell Receptors
Peptides presented by MHC proteins occupy a deep groove flanked by alpha helices
T-cell receptors are antibody-like proteins containing variable and constant regions
CD8 on cytotoxic T cells acts in concert with T-cell receptors
Helper T cells stimulate cells that display foreign peptides bound to class II MHC proteins
Helper T cells rely on the T-cell receptor and CD4 to recognize foreign peptides on antigen-presenting cells
MHC proteins are highly diverse
Human immunodeficiency viruses subvert the immune system by destroying helper T cells
35.5 The Immune System Contributes to the Prevention and the Development of Human Diseases
T cells are subjected to positive and negative selection in the thymus
Autoimmune diseases result from the generation of immune responses against self-antigens
The immune system plays a role in cancer prevention
Vaccines are a powerful means to prevent and eradicate disease
APPENDIX Biochemistry in Focus
Chapter 36 Molecular Motors (Online Only)
36.1 Most Molecular-Motor Proteins Are Members of the P-Loop NTPase Superfamily
Molecular motors are generally oligomeric proteins with an ATPase core and an extended structure
ATP binding and hydrolysis induce changes in the conformation and binding affinity of motor proteins
36.2 Myosins Move Along Actin Filaments
Actin is a polar, self-assembling, dynamic polymer
Myosin head domains bind to actin filaments
Motions of single motor proteins can be directly observed
Phosphate release triggers the myosin power stroke
Muscle is a complex of myosin and actin
The length of the lever arm determines motor velocity
36.3 Kinesin and Dynein Move Along Microtubules
Microtubules are hollow cylindrical polymers
Kinesin motion is highly processive
36.4 A Rotary Motor Drives Bacterial Motion
Bacteria swim by rotating their flagella
Proton flow drives bacterial flagellar rotation
Bacterial chemotaxis depends on reversal of the direction of flagellar rotation
Back Matter
Answers to Problems
Selected Readings
Index