Chapter 02 Chemical Basis of Life (1)

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1、Chapter2TheChemicalBasisofLifeCellsBasisofMolecularDNA‐ProteinInteractionDispositionofAminoAcidResidues1.AtomsElements:substancessuchashydrogenorcarbonthatcannotbebrokendownorconvertedintoothersubstancesbychemicalmeans.Matterismadeofcombinationofelements.Atom:Thesmallestp

2、articleofanelementthatstillremainsitsdistinctivechemicalpropertiesisanatom.Thecharacteristicsofsubstancesotherthanpureelementsdependonwhichatomstheycontain,andthewaytheseatomsarelinkedtogetheringroupstoformmolecules.InsideTheAtomCloudofOrbitingElectronsNucleusCarbonAtomPr

3、otonsandNeutronsElectronicStructureofAtomsNNaTheElectronShellThearrangementofelectronsTheOutermostElectronShell1stshell2electrons2nd8electrons4thshell18electrons3rd8electrons5thshell18electronsTheOutermostElectronShellFilledorunfilledelectronshellsAnatomismoststablewhenit

4、soutermostelectronshellisfilled.TheoutermostelectronsdeterminehowatomsinteractIonicBond:formedbythegainandlossofelectrons.CovalentBond:formedbythesharingofelectrons.ElementsinLivingOrganismsOrganismsLivinginElementsShellsElectronUnfilledandFilledMostAbundantAtomsinOrganis

5、msElectronsneededElementIIItoachievestabilityHydrogen(H)1Carbon(C)4Nitrogen(N)3Oxygen(O)2These4elementsmakeup96.5%ofanorganism’sweight.2.ChemicalBondsCovalentBondsInteractionsbetweenatomsthatmakeupamoleculedependingonsharedelectronsNoncovalentBondsInteractionsbetweenmolec

6、ulesordifferentpartsofalargebiologicalmoleculedependingonattractiveforcesbetweenatomshavinganoppositecharge.CovalentBondsAmoleculeisaclusterofatomsheldtogetherbycovalentbonds,inwhichelectronsaresharedbetweenatoms.Thesharedelectronscompletetheoutershellsofbothatoms.Covalen

7、tBondsInteractionsbetweenatomsthatmakeupamoleculedependingonsharedelectrons.CovalentBondsCovalentBondsCovalentBondsTypesofCovalentBondsSingleBondDoubleBondTripleBondQuadrupleBondCovalentbondsvaryinstrength,posessparticulargeometries.TypesofCovalentBondsPolarCovalentBondsT

8、heelectronsbetweentwounlikeatomsaresharedunequally.PolarandNonpolarCovalentBondsPolarCovalentBon