Sinh học - Chapter 04: Carbon and the molecular diversity of life

Carbon and the Molecular Diversity of LifeChapter 4Overview: Carbon: The Backbone of LifeLiving organisms consist mostly of carbon-based compoundsCarbon is unparalleled in its ability to form large, complex, and diverse moleculesProteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds© 2011 Pearson Education, Inc.Concept 4.1: Organic chemistry is the study of carbon compoundsOrganic chemistry is the study of compounds that contain carbonOrganic compounds range from simple molecules to colossal onesMost organic compounds contain hydrogen atoms in addition to carbon atoms© 2011 Pearson Education, Inc.Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atomsElectron configuration is the key to an atom’s characteristicsElectron configuration determines the kinds and number of bonds an atom will form with other atoms© 2011 Pearson Education, Inc.The Formation of Bonds with CarbonWith four valence electrons, carbon can form four covalent bonds with a variety of atomsThis tetravalence makes large, complex molecules possibleIn molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shapeHowever, when two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons© 2011 Pearson Education, Inc.Figure 4.3Name andCommentMolecularFormula(a) Methane(b) EthaneCH4Ball-and-Stick ModelSpace-FillingModel(c) Ethene (ethylene)C2H6C2H4StructuralFormulaThe electron configuration of carbon gives it covalent compatibility with many different elementsThe valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules© 2011 Pearson Education, Inc.Figure 4.4Hydrogen(valence  1)Oxygen(valence  2)Nitrogen(valence  3)Carbon(valence  4)Molecular Diversity Arising from Carbon Skeleton VariationCarbon chains form the skeletons of most organic moleculesCarbon chains vary in length and shape© 2011 Pearson Education, Inc.Figure 4.5(a) LengthEthane1-Butene(c) Double bond position2-ButenePropane(b) Branching(d) Presence of ringsButane2-Methylpropane(isobutane)CyclohexaneBenzeneHydrocarbonsHydrocarbons are organic molecules consisting of only carbon and hydrogenMany organic molecules, such as fats, have hydrocarbon componentsHydrocarbons can undergo reactions that release a large amount of energy© 2011 Pearson Education, Inc.Figure 4.6NucleusFat droplets(b) A fat molecule(a) Part of a human adipose cell10 mIsomersIsomers are compounds with the same molecular formula but different structures and propertiesStructural isomers have different covalent arrangements of their atomsCis-trans isomers have the same covalent bonds but differ in spatial arrangementsEnantiomers are isomers that are mirror images of each other© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Animation: Isomers Right-click slide / select “Play”Figure 4.7a(a) Structural isomersFigure 4.7b(b) Cis-trans isomerscis isomer: The two Xsare on the same side.trans isomer: The two Xsare on opposite sides.Figure 4.7c(c) EnantiomersCO2HCO2HCH3HNH2L isomerNH2CH3HD isomerFigure 4.5(a) LengthEthane1-Butene(c) Double bond position2-ButenePropane(b) Branching(d) Presence of ringsButane2-Methylpropane(isobutane)CyclohexaneBenzeneEnantiomers are important in the pharmaceutical industryTwo enantiomers of a drug may have different effectsUsually only one isomer is biologically activeDiffering effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules © 2011 Pearson Education, Inc.Figure 4.8DrugIbuprofenAlbuterolConditionEffectiveEnantiomerIneffectiveEnantiomerPain;inflammationAsthmaS-IbuprofenR-IbuprofenR-AlbuterolS-AlbuterolConcept 4.3: A few chemical groups are key to the functioning of biological moleculesDistinctive properties of organic molecules depend on the carbon skeleton and on the molecular components attached to itA number of characteristic groups can replace the hydrogens attached to skeletons of organic molecules© 2011 Pearson Education, Inc.The Chemical Groups Most Important in the Processes of LifeFunctional groups are the components of organic molecules that are most commonly involved in chemical reactionsThe number and arrangement of functional groups give each molecule its unique properties © 2011 Pearson Education, Inc.Figure 4.UN02EstradiolTestosteroneThe seven functional groups that are most important in the chemistry of life:Hydroxyl groupCarbonyl groupCarboxyl groupAmino groupSulfhydryl groupPhosphate groupMethyl group© 2011 Pearson Education, Inc.Figure 4.9-aSTRUCTURECHEMICALGROUPHydroxylNAME OFCOMPOUNDEXAMPLEEthanolAlcohols (Their specific namesusually end in -ol.)(may be written HO—)CarbonylKetones if the carbonyl group iswithin a carbon skeletonAldehydes if the carbonyl groupis at the end of the carbon skeletonCarboxylAcetic acidAcetonePropanalCarboxylic acids, or organic acidsFUNCTIONALPROPERTIES• Is polar as a result of the electrons spending more time near the electronegative oxygen atom.• Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars.• A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal.• Ketone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups).• Found in cells in the ionized form with a charge of 1 and called a carboxylate ion.NonionizedIonized• Acts as an acid; can donate an H+ because the covalent bond between oxygen and hydrogen is so polar:Figure 4.9aSTRUCTUREEXAMPLEAlcohols(Their specificnames usuallyend in -ol.)NAME OFCOMPOUNDFUNCTIONALPROPERTIES(may be written HO—)Ethanol• Is polar as a result of the electrons spending more time near the electronegative oxygen atom.• Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars.HydroxylFigure 4.9bCarbonylSTRUCTUREEXAMPLEKetones if the carbonylgroup is within acarbon skeletonNAME OFCOMPOUNDFUNCTIONALPROPERTIESAldehydes if the carbonylgroup is at the end of thecarbon skeletonA ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal.AcetonePropanalKetone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups).CarboxylSTRUCTUREEXAMPLECarboxylic acids, or organicacidsNAME OFCOMPOUNDFUNCTIONALPROPERTIESAcetic acid• Acts as an acid; can donate an H+ because the covalent bond between oxygen and hydrogen is so polar:• Found in cells in the ionized form with a charge of 1– and called a carboxylate ion. NonionizedIonizedFigure 4.9cAminoAminesGlycineSTRUCTUREEXAMPLE• Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms):NAME OFCOMPOUNDFUNCTIONALPROPERTIES• Found in cells in the ionized form with a charge of 1.NonionizedIonizedFigure 4.9dSulfhydrylThiols (may bewritten HS—)STRUCTUREEXAMPLE• Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein structure.NAME OFCOMPOUNDFUNCTIONALPROPERTIES• Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair. Straight hair can be “permanently” curled by shaping it around curlers and then breaking and re-forming the cross-linking bonds.CysteineFigure 4.9eFigure 4.9fPhosphateSTRUCTUREEXAMPLENAME OFCOMPOUNDFUNCTIONALPROPERTIESOrganic phosphatesGlycerol phosphate• Contributes negative charge to the molecule of which it is a part (2– when at the end of a molecule, as at left; 1– when located internally in a chain of phosphates).• Molecules containing phosphate groups have the potential to react with water, releasing energy.Figure 4.9gMethylSTRUCTUREEXAMPLENAME OFCOMPOUNDFUNCTIONALPROPERTIESMethylated compounds5-Methyl cytidine• Addition of a methyl group to DNA, or to molecules bound to DNA, affects the expression of genes.• Arrangement of methyl groups in male and female sex hormones affects their shape and function.ATP: An Important Source of Energy for Cellular ProcessesOne phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups© 2011 Pearson Education, Inc.Figure 4. UN04AdenosineThe Chemical Elements of Life: A ReviewThe versatility of carbon makes possible the great diversity of organic moleculesVariation at the molecular level lies at the foundation of all biological diversity© 2011 Pearson Education, Inc.