A Chemical Connection to BiologySlide 2Essential Elements of LifeIntroduction to BiochemistryIntroduction to BiochemistryEnergy Levels of ElectronsValences for the major elements of organic moleculesSlide 8Slide 9ElectronegativityHydrogen bondingIonic BondsSaltsMolecular shapes due to hybrid orbitalsSlide 15Introduction to BiochemistrySlide 17Variations in carbon skeletonsTypes of IsomersThe pharmacological importance of enantiomersSlide 21Slide 22Functional groupsFunctional GroupsIntroduction to BiochemistryThe Structure and Function of Large Biological MoleculesThe Synthesis and Breakdown of PolymersSlide 28CarbohydratesCarbohydrates serve as fuel and building materialDisaccharidesPolysaccharidesPolysaccharidesStructural PolysaccharidesCelluloseLipids are a diverse group of hydrophobic moleculesThe synthesis and structure of a fat, or triacylglycerolExamples of saturated and unsaturated fats and fatty acidsPhospholipidsPhospholipid bilayersSteroidsIntroduction to BiochemistrySlide 43PolypeptidesAmino Acid PolymersFour Levels of Protein StructureSlide 47Slide 48Slide 49Slide 50Sickle-Cell Disease: A Change in Primary StructureSlide 52Nucleic AcidsNucleic acids store and transmit hereditary informationThe Structure of Nucleic AcidsNucleotide MonomersNucleotide PolymersThe DNA Double HelixThe DNA double helix and its replicationA Chemical Connection to Biology•Biology is a multidisciplinary scienceLiving organisms are subject to basic laws of physics and chemistry•Matter consists of chemical elements in pure form and in combinations called compounds•Organisms are composed of matter•Matter is anything that takes up space and has mass•Matter is made up of elements •An element is a substance that cannot be broken down to other substances by chemical reactions•A compound is a substance consisting of two or more elements in a fixed ratioA compound has characteristics different from those of its elementsFig. 2-3SodiumChlorineSodiumchlorideEssential Elements of Life•About 25 of the 92 elements are essential to life•Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter•Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur•Trace elements are those required by an organism in minute quantitiesIntroduction to Biochemistry•Valency and Chemical bondselectronegativitytypes of chemical bondsWater•Carboncarbon skeletonsIsomers•Polymerization and macromoleculesmonomers and polymers•Biologically important macromoleculesCarbohydratesLipidsProteinsNucleic AcidsIntroduction to Biochemistry•Valency and Chemical bondselectronegativitytypes of chemical bondsWater•Carboncarbon skeletonsIsomers•Polymerization and macromoleculesmonomers and polymers•Biologically important macromoleculesCarbohydratesLipidsProteinsNucleic AcidsEnergy Levels of Electrons•Potential energy is the energy that matter has because of its location or structure•The electrons of an atom differ in their amounts of potential energy•An electron’s state of potential energy is called its energy level, or electron shellFigure 2.8 Energy levels of an atom’s electronsValences for the major elements of organic moleculesHydrogen(valence = 1)Oxygen(valence = 2)Nitrogen(valence = 3)Carbon(valence = 4)HONCFig. 4.4•Valence electrons are those in the outermost shell, or valence shell•The chemical behavior of an atom is mostly determined by the valence electrons•Elements with a full valence shell are chemically inertFig. 2-9Hydrogen1HLithium3LiBeryllium4BeBoron5BCarbon6CNitrogen7NOxygen8OFluorine9FNeon10NeHelium2HeAtomic numberElement symbolElectron-distributiondiagramAtomic mass2He4.00FirstshellSecondshellThirdshellSodium11NaMagnesium12MgAluminum13AlSilicon14SiPhosphorus15PSulfur16SChlorine17ClArgon18ArThe formation and function of molecules depend on chemical bonding between atoms•Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms•These interactions usually result in atoms staying close together, held by attractions called chemical bonds •A covalent bond is the sharing of a pair of valence electrons by two atoms•In a covalent bond, the shared electrons count as part of each atom’s valence shellElectronegativity•Electronegativity is an atom’s attraction for the electrons in a covalent bondThe more electronegative an atom, the more strongly it pulls shared electrons toward itselfoOxygen = 3.5oNitrogen = 3.0oSulfur & Carbon = 2.5oPhosphorus & Hydrogen = 2.1•In a nonpolar covalent bond, the atoms share the electron equally•In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equallyUnequal sharing of electrons causes a partial positive or negative charge for each atom or moleculeHydrogen bonding•A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atomIn living cells, the electronegative partners are usually oxygen or nitrogen atomsIonic Bonds•Atoms sometimes strip electrons from their bonding partnersAn example is the transfer of an electron from sodium to chlorineAfter the transfer of an electron, both atoms have charges•A charged atom (or molecule) is called an ionA cation is a positively charged ionAn anion is a negatively charged ion•An ionic bond is an attraction between an anion and a cation11 protons10 electrons17 protons18 electronsSalts•Compounds formed by ionic bonds are called ionic compounds, or salts•Salts, such as sodium chloride (table salt), are often found in nature as crystalsMolecular shapes due to hybrid orbitals•A molecule’s shape is very important to its functionDetermined by the positions of its atoms’ valence orbitals•Biological molecules recognize and interact with each other with a specificity based on molecular shapeMolecules with similar shapes can have similar biological effectsFig. 2-18(a) Structures of endorphin and morphine(b) Binding to endorphin receptorsNaturalendorphinEndorphinreceptorsMorphineBrain cellMorphineNatural endorphinKeyCarbonHydrogenNitrogenSulfurOxygenIntroduction to Biochemistry•Valency and Chemical bondselectronegativitytypes of chemical bondsWater•Carboncarbon skeletonsIsomers•Polymerization and macromoleculesmonomers and polymers•Biologically important