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1、13NATURE’SGIANTMOLECULES:THEPLANTKINGDOM13.1Introduction13.2SimpleCarbohydrates(SmallMolecules)13.3Cellulose13.4Cotton13.5Paper13.6Starch13.7OtherCarbohydratePolymers13.8Lignin13.9Bitumens13.10OtherNaturalProductsfromPlants13.11PhotosynthesisGlossaryReviewQuestionsBibliographyAnswerstoReviewQuest
2、ions13.1INTRODUCTIONNaturalpolymers(giantmolecules)arewellknownandhavebeenessentialforhumanlifeforthousandsofyears.Starch,cellulose,lignin,andrubberarepolymersGiantMolecules:EssentialMaterialsforEverydayLivingandProblemSolving,SecondEdition,byCharlesE.Carraher,Jr.ISBN0-471-27399-6Copyright#2003Jo
3、hnWiley&Sons,Inc.307308NATURE’SGIANTMOLECULES:THEPLANTKINGDOMoftheplantkingdomandareessentialforfoodandshelter.Thesepolymersareproducedatanannualrateofmillionsoftons.NaturalrubberwillbediscussedinChapter12.Polymersoftheanimalkingdom,namely,proteins,nucleicacids,chitin,andglycogen,whicharealsoesse
4、ntialproducts,areproducedatannualratesofoveramilliontons.Someofthesenaturallyoccurringgiantmoleculesareclassifiedasbiopolymers,buttheirbehaviorfollowsthesamelawsasthosefollowedbysyn-theticpolymers.ThesenaturallyoccurringgiantmoleculesoftheanimalkingdomarediscussedinChapter14.Whilethetopicsofnuclei
5、cacidsandproteinsaredealtwithinthenextchapter,theyarealsoessentialplantmaterial.Forinstance,nucleicacidsarethegenematerialforbothplantsandanimals.13.2SIMPLECARBOHYDRATES(SMALLMOLECULES)In1812,Gay-Lussacshowedthatcarbohydrates,suchasstarchandcellulose,con-tained45%carbon,49%oxygen,and6%hydrogenbyw
6、eight.Afterdividingthesepercentagesbytheappropriatemassnumbers,oneobtainstheempiricalorsimplestformulaofCH2O.Hence,Gay-Lussaccalledstarchandcellulose‘‘wateredcarbon’’orcarbohydrates.BothstarchandcellulosearepolymersofD-glucose,buttheydifferinthemannerinwhichthesebuildingblocksorrepeatingunitsarej
7、oinedtogetherinthesegiantmolecules.Asshownbythechemicalandskeletalformulasforglyceraldehyde(2,3-dihy-droxypropanal),thissimplecompoundandallhigher-molecular-weightaldo-carbohydratescontainhydroxyl(OH)andcarbonyl(CO
