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1、8885d_c03_07512/23/0310:16AMPage75mac111mac111:reb:––chapter3++AMINOACIDS,PEPTIDES,ANDPROTEINS3.1AminoAcids75acids,covalentlylinkedincharacteristiclinearsequences.3.2PeptidesandProteins85Becauseeachoftheseaminoacidshasasidechainwithdistinctivechemicalpro
2、perties,thisgroupof20pre-3.3WorkingwithProteins89cursormoleculesmayberegardedasthealphabetin3.4TheCovalentStructureofProteins96whichthelanguageofproteinstructureiswritten.3.5ProteinSequencesandEvolution106Whatismostremarkableisthatcellscanproduceproteins
3、withstrikinglydifferentpropertiesandactivi-tiesbyjoiningthesame20aminoacidsinmanydiffer-entcombinationsandsequences.FromthesebuildingThewordproteinthatIproposetoyou...Iwouldwishtoblocksdifferentorganismscanmakesuchwidelydiversederivefromproteios,becausei
4、tappearstobetheproductsasenzymes,hormones,antibodies,trans-primitiveorprincipalsubstanceofanimalnutritionthatporters,musclefibers,thelensproteinoftheeye,feath-plantspreparefortheherbivores,andwhichthelatterers,spiderwebs,rhinoceroshorn,milkproteins,antib
5、i-otics,mushroompoisons,andmyriadothersubstancesthenfurnishtothecarnivores.havingdistinctbiologicalactivities(Fig.3–1).Among—J.J.Berzelius,lettertoG.J.Mulder,1838theseproteinproducts,theenzymesarethemostvar-iedandspecialized.Virtuallyallcellularreactions
6、arecatalyzedbyenzymes.roteinsarethemostabundantbiologicalmacromol-ProteinstructureandfunctionarethetopicsofthisPecules,occurringinallcellsandallpartsofcells.Pro-andthenextthreechapters.Webeginwithadescrip-teinsalsooccuringreatvariety;thousandsofdifferent
7、tionofthefundamentalchemicalpropertiesofaminokinds,ranginginsizefromrelativelysmallpeptidestoacids,peptides,andproteins.hugepolymerswithmolecularweightsinthemillions,maybefoundinasinglecell.Moreover,proteinsexhibitenormousdiversityofbiologicalfunctionand
8、arethe3.1AminoAcidsmostimportantfinalproductsoftheinformationpath-waysdiscussedinPartIIIofthisbook.ProteinsaretheProteinArchitecture—AminoAcidsmolecularinstrumentsthroughwhichgeneticinforma-Proteinsarepolymersofaminoacids,
