Organic Compounds
advertisement
2 The Chemical Level of Organization Matter: Atoms and Molecules Atoms • Smallest unit of an element • Subatomic particles • Protons: (+) charge • Neutrons: neutral • Electrons: (-) charge Matter: Atoms and Molecules Structure of an atom • Nucleus • Protons • Neutrons • Electron Shell Matter: Atoms and Molecules Structure of atom • Atomic number • Equals number of protons • Atomic mass • Equals protons + neutrons • Isotopes of element • Reflects number of neutrons • Atomic weight • Averages isotope abundance Matter: Atoms and Molecules Structure of atom • Electrons surround nucleus • Electrons organized in shells • The outer shell determines chemical properties Matter: Atoms and Molecules Atoms and Electron Shells Matter: Atoms and Molecules Key Note All matter is composed of atoms in various combinations. Their interactions establish the foundations of physiology at the cellular level. Matter: Atoms and Molecules Chemical Bonds and Compounds • Atoms bond in chemical reactions • Reactions transfer electrons • Electrons are gained, lost, or shared • Molecules or compounds result • Compounds contain several elements Matter: Atoms and Molecules Ionic Bonds • Atoms gain or lose electrons • Charged atoms are ions • Ions bear (+) or (-) charge • Cations have (+) charge • Anions have (-) charge • Cations and anions attract • Ions form bonds Matter: Atoms and Molecules Ionic Bonding Matter: Atoms and Molecules Sodium chloride crystal Matter: Atoms and Molecules Matter: Atoms and Molecules Covalent bonds • Some atoms share electrons • Shared electrons complete outer shell • Sharing atoms bond covalently • Single covalent bond • One shared electron • Double covalent bond • Two shared electrons Matter: Atoms and Molecules Covalent Bonds Matter: Atoms and Molecules Nonpolar and Polar Covalent Bonds • Equal electron sharing • Nonpolar covalent bonds • Example: carbon-carbon bonds • Non-equal electron sharing • Polar covalent bonds • Example: oxygen-hydrogen bonds Matter: Atoms and Molecules Hydrogen bonds • Weak attractive force • Between two neighboring atoms • A polar-bonded hydrogen, and • A polar-bonded oxygen or nitrogen • For example, between water molecules Matter: Atoms and Molecules Hydrogen Bonds Chemical Notation A chemical “shorthand” • Simplified descriptions of: • Compounds • Structures • Reactions • Ions • Abbreviations of elements • Abbreviations of molecules Chemical Reactions Metabolism All the chemical reactions in the body • Consumes reactants • Produces products • Breaks or makes chemical bonds between atoms Chemical Reactions Basic Energy Concepts • Work—movement or change in matter’s physical structure • E.g., running, synthesis • Energy—ability to do work • Kinetic energy • Potential energy Chemical Reactions Basic Energy Concepts (continued) • Potential energy—stored energy • E.g., leopard lurks in a tree • Kinetic energy—energy of movement • E.g., leopard pounces on prey Chemical Reactions 3 types of reactions • Decomposition—breaks molecule into smaller pieces • Synthesis—assembles smaller pieces into larger one • Exchange—shuffles pieces between molecules Chemical Reactions Decomposition Reactions • In chemical notation: • AB A + B • Releases covalent bond energy • Hydrolysis—Decomposition reaction with H•OH • E.g., food digestion • Catabolism—Sum of all the body’s decomposition reactions Chemical Reactions Synthesis Reactions • In chemical notation: • A + B AB • Absorbs energy • Formation of new bonds • Dehydration synthesis • Removal of H•OH between molecules • Anabolism—Sum of the body’s synthesis reactions Chemical Reactions Exchange Reaction • In chemical notation: • AB + CD AC + BD • Decomposition and synthesis Chemical Reactions Reversible Reactions • A + B AB • Equilibrium—Condition when the forward and reverse reactions occur at the same rate Chemical Reactions Key Note When energy is exchanged, heat is produced. Heat raises local temperatures, but cells cannot capture it or use it to perform work. Enzymes and Reactions Activation Energy Quantity of energy needed to start a chemical reaction • Catalysts reduce activation energy to speed reaction • Enzymes catalyze cellular reactions Enzymes and Reactions Enzymes and Activation Energy Enzymes and Reactions Exergonic—Reactions that release energy • E.g., decomposition reactions Endergonic—Reactions that consume energy • E.g., synthesis reactions Inorganic Compounds Nutrients Essential elements and molecules obtained from the diet Metabolites Molecules synthesized or broken down by chemical reactions inside the body Inorganic Compounds Inorganic Smaller molecules such as water and oxygen that lack carbon and hydrogen Organic Larger molecules such as sugars, proteins, and fats composed largely of carbon and hydrogen Inorganic Compounds Carbon Dioxide (CO2) • Gas produced by cellular metabolism and released into the atmosphere via the lungs Oxygen (O2) • Atmospheric gas consumed by cells in order to produce energy Inorganic Compounds Water and its properties • Most important body chemical • Excellent solvent • High heat capacity • Essential chemical reactant Inorganic Compounds Water Dissociates Ionic Bonds Inorganic Compounds Key Note Water accounts for most of your body weight. Proteins, key components of cells, and nucleic acids, which control cells, work only in solution. Inorganic Compounds Inorganic Acids and Bases • Acid—Releases hydrogen ions (H+) into solution • E.g., HCl H+ + Cl• Base—Removes hydrogen ions from solution • E.g., NaOH + H+ Na+ + H•0H Inorganic Compounds pH A measure of hydrogen ion concentration in a solution • Neutral solution—pH = 7 • Acidic solution—pH below 7 • Basic solution—pH above 7 Inorganic Compounds pH and Hydrogen Ion Concentration Inorganic Compounds Buffers • Maintain pH within normal limits (pH 7.35 to pH 7.45) • Release hydrogen ions if body fluid is too basic • Absorb hydrogen ions if body fluid is too acidic Inorganic Compounds Salt An ionic compound not containing H+ or OH•Salts are electrolytes •Electrolytes dissociate in water • E.g., NaCl Na+ + Cl•Electrolytes carry electrical currents in the body Organic Compounds Organic Compounds • Contain carbon, hydrogen, and usually oxygen • Important classes of organic compounds include: • Carbohydrates • Lipids • Proteins • Nucleic acids Organic Compounds Carbohydrates • Most important energy source for metabolism • Three major types • Monosaccharides (E.g., glucose) • Disaccharides (E.g., sucrose) • Polysaccharides (E.g., glycogen) Organic Compounds Glucose Organic Compounds Formation and Breakdown of Complex Sugars Organic Compounds Formation of Glycogen Organic Compounds Organic Compounds Lipids • Water-insoluble • Four important classes • Fatty acids • Fats • Steroids • Phospholipids Organic Compounds Organic Compounds Fatty Acids Organic Compounds Triglycerides— Formed by three fatty acid molecules bonding to a glycerol molecule Organic Compounds Cholesterol • Building block for steroid hormones • Component of cell membranes Organic Compounds Phospholipids • Most abundant membrane lipid • Diglyceride • Two fatty acids + glycerol • Water-soluble and water-insoluble parts Organic Compounds A Phospholipid Molecule Organic Compounds Proteins • Most abundant organic component in human body • About 100,000 different proteins • Contain carbon, nitrogen, oxygen, hydrogen, and a bit of sulfur Organic Compounds Proteins play vital roles • Support • Movement • Transport • Buffering • Regulation • Defense Organic Compounds Proteins are built from amino acids Organic Compounds Peptide bonds join amino acids into long strings Organic Compounds Protein Structure Organic Compounds Protein Structure • “R” groups interact with their neighbors and with solvent • Amino acid chain folds and twists into complex shape • Final shape determines function • High fever distorts shape • Distorted proteins don’t work Organic Compounds Enzyme Function • Substrates (reactants) bind to active site on enzyme surface • Binding lowers activation energy needed for reaction • Substrates react to form product • Product is released from enzyme surface Organic Compounds Enzyme function made simple Organic Compounds Nucleic Acids • Large molecules • Built from atoms of C, H, O, N, and P (What are these elements?) • Store and process molecular information • Two classes of nucleic acid • DNA (deoxyribonucleic acid) • RNA (ribonucleic acid) Organic Compounds The Structure of Nucleic Acids Organic Compounds Structure of Nucleic Acids • Nucleotides contain a sugar, a phosphate, and a base • Sugar-phosphate bonds link nucleotides in long strands • Hydrogen bonds hold two DNA strands in a double helix High-Energy Compounds • Catabolism releases energy • Cells store energy in high-energy compounds • High-energy compounds drive endergonic reactions • ATP is the most important high-energy compound in cells • ATP keeps cells alive! High-Energy Compounds Structure of ATP Summary of Body Chemistry Organic Chemical Building Blocks
