Chapter 4Overview: Carbon—The Backbone of Biological MoleculesConcept 4.2: Carbon atoms can form diverse molecules by bonding to four other atomsThe Formation of Bonds with CarbonSlide 5LE 4-3Slide 7LE 4-4Molecular Diversity Arising from Carbon Skeleton VariationLE 4-5HydrocarbonsLE 4-6IsomersLE 4-7Slide 15LE 4-8Concept 4.3: Functional groups are the parts of molecules involved in chemical reactionsThe Functional Groups Most Important in the Chemistry of LifeSlide 19LE 4-9Functional GroupsExamples of Functional GroupsSlide 23LE 4-10aaLE 4-10abLE 4-10acLE 4-10baLE 4-10bbLE 4-10bcATP: An Important Source of Energy for Cellular ProcessesThe Chemical Elements of Life: A ReviewCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures for Biology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 4Chapter 4Carbon and the Molecular Diversity of LifeCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: Carbon—The Backbone of Biological Molecules•Although cells are 70–95% water, the rest consists mostly of carbon-based compounds•Carbon is unparalleled in its ability to form large, complex, and diverse molecules•Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compoundsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms•Electron configuration is the key to an atom’s characteristics•Electron configuration determines the kinds and number of bonds an atom will form with other atomsCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Formation of Bonds with Carbon•With four valence electrons, carbon can form four covalent bonds with a variety of atoms•This tetravalence makes large, complex molecules possibleCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape•However, when two carbon atoms are joined by a double bond, the molecule has a flat shapeLE 4-3LE 4-3MolecularFormulaStructuralFormulaBall-and-StickModelSpace-FillingModelMethaneEthaneEthene (ethylene)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•The electron configuration of carbon gives it covalent compatibility with many different elements•The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living moleculesLE 4-4LE 4-4Hydrogen(valence = 1)Oxygen(valence = 2)Nitrogen(valence = 3)Carbon(valence = 4)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsMolecular Diversity Arising from Carbon Skeleton Variation•Carbon chains form the skeletons of most organic molecules•Carbon chains vary in length and shapeLE 4-5LE 4-5LengthEthanePropaneButane2-methylpropane(commonly called isobutane)BranchingDouble bondsRings1-Butene 2-ButeneCyclohexane BenzeneCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsHydrocarbons•Hydrocarbons are organic molecules consisting of only carbon and hydrogen•Many organic molecules, such as fats, have hydrocarbon components•Hydrocarbons can undergo reactions that release a large amount of energyLE 4-6LE 4-6A fat molecule Mammalian adipose cells100 µmFat droplets (stained red)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsIsomers•Isomers are compounds with the same molecular formula but different structures and properties:–Structural isomers have different covalent arrangements of their atoms–Geometric isomers have the same covalent arrangements but differ in spatial arrangements–Enantiomers are isomers that are mirror images of each otherAnimation: IsomersAnimation: IsomersLE 4-7LE 4-7Structural isomers differ in covalent partners, as shown in this example of two isomers of pentane.Geometric isomers differ in arrangement about a double bond. In these diagrams, X represents an atom or group of atoms attached to a double-bonded carbon.cis isomer: The two Xsare on the same side.trans isomer: The two Xsare on opposite sides.L isomer D isomerEnantiomers differ in spatial arrangement around an asymmetric carbon, resulting in molecules that are mirror images, like left and right hands. The two isomers are designated the L and D isomers from the Latin for left and right (levo and dextro). Enantiomers cannot be superimposed on each other.Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•Enantiomers are important in the pharmaceutical industry•Two enantiomers of a drug may have different effects•Ex: Thalidomide . One reduced morning sickness and other caused birth defects.•Ex: L-Dopa aliviates Parkinson’s disease and its isomer D-Dopa is inactive.LE 4-8LE 4-8L-Dopa(effective againstParkinson’s disease)D-Dopa(biologicallyInactive)Copyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsConcept 4.3: Functional groups are the parts of molecules involved in chemical reactions•Distinctive properties of organic molecules depend not only on the carbon skeleton but also on the molecular components attached to it•Certain groups of atoms are often attached to skeletons of organic moleculesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Functional Groups Most Important in the Chemistry of Life•Functional groups are the components of organic molecules that are most commonly involved in chemical reactions•The number and arrangement of functional groups give each molecule its unique propertiesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings•Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules •Ex: the molecules of the female hormone estradiol and the male hormone testosterone have both the same basic 4 carbon rings. They only differ in the functional groups attached.LE 4-9LE 4-9EstradiolTestosteroneMale lionFemale lionCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsFunctional Groups•Atoms or clusters of atoms that are covalently bonded to carbon backbone•Give organic compounds their different propertiesCopyright © 2005 Pearson Education, Inc. publishing as Benjamin CummingsExamples of Functional GroupsHydroxyl