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1、TextACarbohydratesManycarbohydrates（碳水化合物）canbeexpressedintheform[Cx（H20）y],butthisisnotanaccuratedescriptionoftheirstructure.Carbohydratesareinfactpolyhydroxy（多疑棊）aldehydes（醛）orketones（酮）andthetermalsoincludesanycompoundsthatcanbehydrolyzedtoformcarbohydrates.Thesimplestcarbohydratesarecalled
2、sugars（ormonosaccharides（单糖））andthesemaylinktogethertoformmorecomplexcarbohydrates,starches（orpolysaccharides（多糊））・Thediversityofdietarycarbohydratesnecessitatesdiscussionofseveralclassesofthesemolecules,rangingfromsimplesugarstohuge,branchedpolymers.1.MonosaccharidesMonosaccharidesorsimplesug
3、arsareeitherhexoses（6-carbon）（六碳糖）likeglucose（葡萄糖），galactose（半乳糖）andfructose（果糖），orpentoses（5-carbon）（五碳糖）likeribose（核糖）・Thesearethebreakdownproductsofmorecomplexcarbohydratesandcanbeefficientlyabsorbedacrossthewallofthedigestivetube（消彳匕道）andtransportedintoblood・Simplesugarsaremonosaccharides.
4、Thesearecharacterisedbyhydroxyl（疑基），aldehydeandketonegroups（功能团）.Monosaccharidesareeitheraldoses（醛糖）orketoses（酮糖）.Thealdo-andketo-prefix（前缀）identifiesthenatureofthecarbonyl（碳棊，碳酰）group,andthe-osesuffix（后缀）designatesacarbohydrate・InFischerprojections（费歇尔投影式）,ifthehydroxylgroupattheloweststereog
5、eniccentre（手相中心）,C5inthiscase,pointstotheright,itmaybelabelledaD-sugar,ifitpointstotheleft,itisanL-sugar.Thenumberofcarbonatomsisalsoindicated,soforexample,aldohexoseisthesix-carbonaldehydesugar,moreconunonlyreferredtoasglucose・Intramolecular（分子内），nucleophilicaddition（亲核加成）cantakeplacebetweena
6、hydroxylandacarbonylgroupofthesamemolecule,resultinginthefc）nnationofacyclichemiacetal（半写g醛）•Simplemonosaccharidesconsistofaldehydeorketonegroupsandbothprimaryandsecondaryhydroxylgroups,allofwhichareavailableforreaction.Analkaline（碱的，强碱的）solutionofcopper（铜）（Fehling'ssolution（斐林试剂））oxidises（氧化）
7、analdosetoanaldonate（醛糖蛊h）,andisitselfreducedtocopper,precipitating（沉淀）asredCu2O.Hydrogenation（红化作用）offructose,andcarbohydratesingeneral,involvesadditionofhydrogen（氢）tothedoublebond（双键）ofthecarbonylgroup.Theresultingproductshavean-itols
