生化代谢整合

Chapter28VitaminsOBJECTIVEANDREQUIREMENT【StudentsShouldGainaMasteryof】1.functionoffolicacid,niacin,pantothenicacidandbiotin2..functionofvitaminB1,B2,B6,B12,3..functionofvitaminA,C,D,E,K4.classificationofvitamin【StudentsShouldGainaFamiliaritywith】1.deficiencyofvitaminandclinicalindications2.metabolismofvitamin3.toxicityofsomevitaminI.OverviewTheconceptofvitamine(Definitions)Vitaminsareorganicchemicalcompoundsnecessaryforgrowth,health,normalmetabolismandphysicalwell-being.Theycanbefoundinsufficientquantitiesinthefoodsyoueat.Youneedvitaminsonlyinsmallamounts.CharacterofVitamins

A.OrganicContaincarbon

B.Notsynthesizedbythebody

Essentialthatdietsupplyvitamins

C.Neededinsmallamounts 1.milligram(mg)quantities(1/1000ofa gram) 2.microgram(mg)quantities1/1,000,000 ofagram

D.Dietarydeficiency

disease

1.Diseasecuredbyrepletionofvitamin

VitaminscommonlylackingintheAmericandietVitaminA、VitaminC、VitaminD、VitaminE

E.

Derivedfromplantsandanimalsprimarily 1.Somevitaminscomefrommicrobes

a.VitaminK,B12 2.Vitaminsexistinseveralstates

a.NaturalvsSyntheticCharacterofVitamins11typesnesessaryforhumanbeingClassificationofVitaminsWaterSolubleVitaminsII.FolicAcid/FolacinStructurepteridinering-PABA-glutamateStabilityverysensitivetoheateasilyoxidizedleachedA.FunctionoffolicacidFolicacidtakepartinsinglecarbonmetabolismandprovidingone-carbonresiduesfornucleicacidsynthesisB.NutritionalanemiasFolateDeficiency

MegaloblasticAnemiadecreasedDNAsynthesisfailureofbonemarrowcellstodividenormalproteinsynthesisresultsinlargeimmatureRBC’scontrastwithmicrocytichypochromicanemiaFolateDeficiencyHomocysteineCoronaryHeartDiseaseriskfactor?genetichomocystinuria-prematureCHDhi[homocys]relatedtohiCHDrisklo[folate,B-12,B-6]relatedtohiCHDrisklointakeofB-vitrelatedtohiCHDriskDefectsinformationofneuraltube(brain&spinalcord)AnencephalyabsenceofcerebralhemispheresSpinabifidaFirsttwomonthsgestationFolateandNeuralTubeDefects(NTD)III.Cobalamin(vitaminB12)A.StructureofcobalaminanditscoenzymeformscobalaminemethylcobalaminetransportandcoenzymeformadenosylcobalaminestorageandcoenzymeformDigestion&AbsorptionofB12IntrinsicFactorgastricglycoproteinbindswithB12insmallintestineIF-B12complexbindstoB12receptorinileumforabsorptionB12absorptionrequiresfunctioningstomach,pancreas,andileumC.FolattraphypothesisB-12DeficiencyPerniciousanemiamegaloblasticanemiaMethyl-folatetrapDelayedorfailureofnormalcelldivisionduetoimpairedDNAsynthesisneuropathydefectivemyelinationprogressiveperipheralweakeningunresponsivetofolateupperlimittofolatesupplementation/enrichmentChemicalStructureIV.Ascorbicacid(vitaminC)Hydroxylationofprolineandlysine

（CollagenSynthesis）A.DeficiencyofascorbicacidSkin,teeth,strengtheningbloodvesselwalls,bindingcellsScurvy

BleedinggumspetechiaeeasybruisingimpairedwoundhealingandbonerepairjointpainanemiaVitaminC-ScurvyV.Pyridoxine(vitaminB6)FunctionofvitaminB6Nervefunction,metabolism,synthesisofredbloodcellsA.ClinicalindicationsforvitaminB6Thiaminpyrophosphate:coenzymeformPyrimidineringThiazoleringVI.Thiamine(vitaminB1)AbsorptionofB-1induodenumactivetransport(lowthiaminlevels)requiressodiumandfolicacidpassivetransport(hiB-1levels)phosphorylationtoactiveforminsidecells(TPP)transportedviaportalbloodnosignificantstorage,excesstourinePyruvate+CoA+NAD+------>CO2+acetyl-CoA+NADH+H+

A.ClinicalindicationsforvitaminB1ThiaminDeficiency:Nervoussystemfunction,metabolism

1.Beri-Berianorexia,fatigue,depressioneffectsoncardiovascularsystemnervoussystemWetBeriBerisymptomssimilartocongestiveheartfailurePittingedema-trunk,limbs,facelaboredbreathing,tachycardiarapiddeteriorationfatalcirulatorycollapserespondsrapidlytoB-1supplementsDryBeri-Berinoedemaprogressivewastingnumbingandweakeningofextremitieschronicinfections2.Wernick-KorsakoffsyndromeThisdisease,notablyfrequentamongchronicalcoholics,isduetoadeficiencyofvitaminB1Neurologicsymptomsincludeconfusion,memoryloss,impairedmovementsandperipheralneuropathy.

Immediateadministrationofthiamineisusuallysuccessfulintreatingthesymptoms,butsometimespermanentmemorylossoccurs.NicotinicAcid(Plantform)Nicotinamide(animalform)(reducedform)VII.Niacin(B-3)BiochemicalFunctionsofB-3Oxidation-ReductionReactions(NAD/NADHDehydrogenasesElectronTransportSystemInvolvedinenergyproductionPellegra(roughskin)

Firstreportedin1735byDonGasperCasal,aSpanishphysician,pellagrameans"roughskin."

Primarysymptomsincludethe"3Ds":dementia

(mentalsymptoms),dermatitis

(scalyskinsores),anddiarrhea.NiacinenrichmentofcerealgrainsanddietsadequateinproteinandcalorieseventuallyeradicatedpellagrafromtheUnitedStates.SeasonalepidemicsstilloccurinpartsofSoutheastAsiaandAfrica,however.DementiaandDiarrheaApellagraepidemicemergedduringthe1900sintheUnitedStates,whencorn(maize)begantoreplaceothersourcesofdietaryproteinamongtheruralpoor.Niacinincornistightlyboundtoprotein,andthuspoorlyabsorbed.VIII.Riboflavin(vitaminB2)Riboflavinistheprecursorforthecoenzymesflavinmononucleotide(FMN)andflavinadeninedinucleotide(FAD).Skin,metabolismIX.BiotinBiotinisthecofactorrequiredofenzymesthatareinvolvedincarboxylationreactions,e.g.acetyl-CoAcarboxylaseandpyruvatecarboxylase.X.PantothenicacidPantothenicacidisalsoknownasvitaminB5.Pantothenicacidisformedfromß-alanineandpantoicacid.PantothenateisrequiredforsynthesisofCoAMetabolismLipidsolublevitamins:

VitaminD VitaminA VitaminE VitaminKFatsolublevitaminsFatsolublevitamins,whicharestoredintheliverandfattytissuesofthebody,aregenerallyexcretedmuchmoreslowlythanwatersolublevitamins.Becausetheyarestoredforalongperiod,fatsolublevitaminsgenerallyposeagreaterriskoftoxicitythanwatersolublevitaminswhenconsumedinexcess.D.FunctionofvitaminADeficiencyofVitaminAInfectiousDiseasesNightBlindnessRough,bumpy,dryskinCellHealthandMaintenanceEpithelialcellslinetheoutside(skin)andexternalpassages(mucusformingcells)withinthebodyRetinoicacidinfluenceshowepithelialcellsdifferentiateandmatureWithoutvitaminA,cellswilldeteriorateLeadstofollicularhyperkeratosis(skindisorder)XII.VitaminDA.DistributionofvitaminDTencompoundscalledvitDTheVitaminD’s–D1,D2andD3ThemostimportantareD2(ergocalciferol)andD3(cholecalciferol)TheyexhibitantirachiticpropertiesB.MetabolismofvitaminD

Function:

Promotescalciumandphosphateabsorptionandmobilization;bonesandteethmetabolismVitD3isrequiredinthedietofgrowingchildren

andpregnantwomen.C.FunctionofvitaminDVitD3

activeform:

1,25dihydroxycholecalciferolFunctionsofVitaminDRegulatebloodcalciumlevelOsteoporosis:

ThinningofBonesDietaryfactorsthatbuildbonemassCalciumVitaminDVitaminKOtherpossibledietaryfactors:vitaminC,magnesium,potassium,manganese,zinc,copper,boronVitaminK:K1-phylloquinoneK2-menaquinoneA.Function:

bloodcoagulation,Biosynthesisofcalcium-bindingproteins.XIII.VitaminKVitaminKisnamedfor“koagulation”,orcoagulationinEnglish,becauseitaidsbloodclotting.α-tocopherolXIV.VitaminEVitaminE-associatedwithnormalreproductionandmuscledevelopmentVitaminErelatestofunctionofanimals’reproduction,itisneededforspermandovaproduction.Inaddition，italsohasfunctionofmuscledevelopment.ItsdeficiencycaninduceWhitemusclediseaseWeakmusclesRetainedplacentaReducedreproductionVitaminEmightimprovedairycows’performanceandqualityofmilk.

VitaminE,AnAntioxidant

.VitaminEresidesinthefattypartofcellmembranesprotectingthemfromfreeradicals.26、27、28章的教学组织与安排一、分组讨论1.每个班分成2组，原则上按照学号顺序（每组12-14人）2.每组就如何学习好26、27、28章内容展开讨论，如：必须要掌握哪些知识点？要熟悉哪些内容？要了解哪些知识？需要查阅哪些资料和文献？等等。分组后，哪个（些）组主要讲解26、27、28章的内容？如何讲授？怎样安排实施？等等。二、按照分组进行学生的大班讲授1.