Principles of Medical Biochemistry E-Book

Part ONE PRINCIPLES OF MOLECULAR STRUCTURE AND FUNCTION 1 Chapter 1 INTRODUCTION TO BIOMOLECULES Water Is the Solvent of Life Water Contains Hydronium Ions and Hydroxyl Ions Ionizable Groups Are Characterized by Their pK Values The Blood pH is Tightly Regulated Acidosis and Alkalosis Are Common in Clinical Practice Bonds Are Formed by Reactions between Functional Groups Isomeric Forms Are Common in Biomolecules Properties of Biomolecules Are Determined by Their Noncovalent Interactions Triglycerides Consist of Fatty Acids and Glycerol Monosaccharides Are Polyalcohols with a Keto Group or an Aldehyde Group Monosaccharides Form Ring Structures Complex Carbohydrates Are Formed by Glycosidic Bonds Polypeptides Are Formed from Amino Acids Nucleic Acids Are Formed from Nucleotides Most Biomolecules Are Polymers Summary Chapter 2 INTRODUCTION TO PROTEIN STRUCTURE Amino Acids Are Zwitterions Amino Acid Side Chains Form Many Noncovalent Interactions Peptide Bonds and Disulfide Bonds Form the Primary Structure of Proteins Proteins Can Fold Themselves into Many Shapes a-Helix and ß-Pleated Sheet Are the Most Common Secondary Structures in Proteins Globular Proteins Have a Hydrophobic Core Proteins Lose Their Biological Activities When Their Higher-Order Structure Is Destroyed The Solubility of Proteins Depends on pH and Salt Concentration Proteins Absorb Ultraviolet Radiation Proteins Can Be Separated by Their Charge or Their Molecular Weight Abnormal Protein Aggregates Can Cause Disease Neurodegenerative Diseases Are Caused by Protein Aggregates Protein Misfolding Can Be Contagious Summary Chapter 3 OXYGEN TRANSPORTERS: HEMOGLOBIN AND MYOGLOBIN The Heme Group Is the Oxygen-Binding Site of Hemoglobin and Myoglobin Myoglobin Is a Tightly Packed Globular Protein Red Blood Cells Are Specialized for Oxygen Transport The Hemoglobins Are Tetrameric Proteins Oxygenated and Deoxygenated Hemoglobin Have Different Quaternary Structures Oxygen Binding to Hemoglobin Is Cooperative 2,3-Bisphosphoglycerate Is a Negative Allosteric Effector of Oxygen Binding to Hemoglobin Fetal Hemoglobin Has a Higher Oxygen-Binding Affinity than Does Adult Hemoglobin The Bohr Effect Facilitates Oxygen Delivery Most Carbon Dioxide Is Transported as Bicarbonate Summary 38 Chapter 4 ENZYMATIC REACTIONS 39 The Equilibrium Constant Describes the Equilibrium of the Reaction The Free Energy Change Is the Driving Force for Chemical Reactions The Standard Free Energy Change Determines the Equilibrium Enzymes Are Both Powerful and Selective The Substrate Must Bind to Its Enzyme before the Reaction Can Proceed Rate Constants Are Useful for Describing Reaction Rates Enzymes Decrease the Free Energy of Activation Many Enzymatic Reactions Can Be Described by Michaelis-Menten Kinetics Km and Vmax Can Be Determined Graphically Substrate Half-Life Can Be Determined for First-Order but Not Zero-Order Reactions Kcat/Km Predicts the Enzyme Activity at Low Substrate Concentration Allosteric Enzymes Do Not Conform to Michaelis-Menten Kinetics Enzyme Activity Depends on Temperature and pH Different Types of Reversible Enzyme Inhibition Can Be Distinguished Kinetically Enzymes Stabilize the Transition State Chymotrypsin Forms a Transient Covalent Bond during Catalysis Summary Chapter 5 COENZYMES Enzymes Are Classified According to Their Reaction Type Adenosine Triphosphate Has Two Energy-Rich Bonds ATP Is the Phosphate Donor in Phosphorylation Reactions ATP Hydrolysis Drives Endergonic Reactions Cells Always Try to Maintain a High Energy Charge Dehydrogenase Reactions Require Specialized Coenzymes Coenzyme A Activates Organic Acids S-Adenosyl Methionine Donates Methyl Groups Many Enzymes Require a Metal Ion Summary Part TWO GENETIC INFORMATION: DNA, RNA, AND PROTEIN SYNTHESIS Chapter 6 DNA, RNA, AND PROTEIN SYNTHESIS All Living Organisms Use DNA as Their Genetic Databank DNA Contains Four Bases DNA Forms a Double Helix DNA Can Be Denatured DNA Is Supercoiled DNA Replication Is Semiconservat