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《第十四章 蛋白质和核酸（the fourteenth chapter protein and nucleic acid）》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、第十四章蛋白质和核酸（Thefourteenthchapterproteinandnucleicacid）Thefourteenthchapter:proteinandnucleicacidSection1-aminoacidsTheexistence,classificationandnomenclatureofalphaaminoacidsAminoacidisthehydrogenatomofthecarboxylicacidmoleculeisalkylamino(-NH2)substitutedderivatives,isthebasicunito
2、fprotein.Naturalaminoacidisfoundinabout200kindsofproteinaminoacidsconstituteabout30species,ofwhichtherearemorethan20kindsofcommonpeople,theseaminoacidscalledproteinaminoacids.Nootheraminoacidsinvolvedinproteinsknownasnonproteinaminoacids.Inadditiontoproline,morethan20kindsofcommona
3、minoacidsarealphaaminoacids,andtheirstructurescanbeexpressedbygeneralformula:Alphaaminoacidcanbedividedintoaliphaticalkylaminoacids,aromaticaminoacidsandheterocyclicaminoacids;accordingtomolecularamino(-NH2)andcarboxyl(-COOH)thenumberofdifferentaminoacidscanalsobedividedintoneutral
4、aminoacids(equaltothenumberofcarboxylandamino),acidicaminoacids(aminocarboxylnumberisgreaterthanthenumberofbasicaminoacids(amino),morethanthenumberofcarboxylgroups).Aminoacidsareusuallynamedbythenameaccordingtotheiroriginornature,suchasaminoacidwithsweetcalledglycine,serinefromthee
5、arliestsilknamed.Inuseforthesakeofconvenience,thecommonlyusedEnglishnameabbreviationsandsymbols(usuallythreeletters)orChinesecode.ForexampleGlyorGorglycine"Gan"wordtodenoteitsname.Aminoacidnomenclatureandothersubstitutedcarboxylicacidswiththesamename,theparentcarboxylicacidasthenam
6、e.Aminoacidsthatmakeupproteins,Thereareeightkindsofanimalsthatareunabletosynthesizethemselvesandmustbeobtainedfromfood.Theycausediseasewhentheyaredeficient.Theyarecalledessentialaminoacids.TheaminoacidsthatmakeupproteinsarefoundintableP17714-1Two.Structureandpropertiesofalphaaminoa
7、cids(1)thestructureofalphaaminoacidsAlphaaminoacidsexceptglycine,containingchiralcarbonatoms,withopticalactivity.ItsconfigurationisgenerallyL-(littleD-aminoacidmetabolisminsomebacteria).Thefollowingformulacanbesaid:TheaminoacidsoftypeL-arestructurallydifferentfromthoseoftypeD-amino
8、acids,buttheirphysiologica
