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Starch
o Apolymerofglucosemonomers:majorstorageformofglucoseinplants
o Has(1-4)linkages(straightline)andafew(1-6)linkages(branching)
o Wecandigestthis,astheglucosemonomersareinalpha-configuration
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Glycogen
o Consistsofglucosemonomers:themajorstorageformofglucoseinanimals
o Has(1-4)linkages(straightline)andfrequent(1-6)linkages(branching)
o Wecanbreakthisdowntoreleaseglucosemonomers(alpha-configuration)
o Glycogenbranchesmorethanstarch
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Cellulose
o Isamajorcomponentofthetoughwallsthatencloseplantcells(notethegroupdistribution,linearityand
packingpotential)
o Mammalscannotdigestthis,asglucosemonomersareinbetaconfiguration
o CH2OHandOHalternatesoitcanstackneatlyandformtightstructures
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Glycoproteins
o Combinationofproteinsandcarbohydrates
o Usuallyfoundoncellsurfaces
o Combinationofcarbohydrateunitsandproteinchainscanoftenbeusedasuniqueidentifieroftypesofcells
o Bacteriaandviruseshaveuniquecell-surfaceglycoproteinsthatarerecognisedbyourimmunesystemtoward
offinfection
o Glycoproteinsalsopresentoncellsurfacesofeukaryoticcells,andcanbeusedtodifferentiatebetweencell
types
Chitin
o Foundintheexoskeletonofarthropodsandcellwallsoffungi
o Highlyresistanttoenzymaticdigestion
o Canbeusedassurgicalthread
GlycaemicIndex(GI)
o Isawayofmeasuringhowquicklyyourblood-glucoselevelrisesaftereatingcarbohydrate-containingfoods
o Thequickerthefoodisdigested,thefasteryourbloodglucoselevelrisesàhigherGI
o LowGIfoodsusuallycontainunrefinedcarbsthataredifficulttobreakdown
quickly
o LowGIfoodssatisfycravingsforlongerperiodsoftime,andbeenlinkedto
loweringriskfordiabetes
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DNAReplication
§ BacterialDNAreplication(schematic)
o DNAreplicationstartsatthe‘origin’
o Proceedsinbothdirectionsuntiltheentirechromosomehasbeencopied
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HelicaseuntwiststheDNAhelixtogivesinglestrandedDNA,butincreasescoilingaheadofthereplicationfork
Topoisomerase‘fixes’theincreasedcoilingintheDNAtemplate.Preventssupercoilingbytransiently(notlastinglong)
nickingbothstrandsandallowingthetwostrandstorotatearoundeachother
Single-strandedbindingproteinstabilizesthesinglestrandedtemplate
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DNAsynthesizedusingnucleotidebuildingblocks(ATP,TTP,CTP,GTP)
Alwaysproceedsin5’to3’direction
o Energyforpolymerizationissuppliedbyincomingtriphosphatenucleotide
o Nucleotidesareaddedtothe3’endofthegrowingdaughterstrand–theendatwhichtheDNAstrandhasa
freehydroxylgrouponthe3’carbonofthesugar
DNApolymerasescatalysesDNAsynthesis
ThetwoantiparallelDNAstrandsthatarebeingreplicatedarereferredtoasthe‘leading’andthe‘lagging’strand
o Leadingstrand:strandthatisreplicatedcontinuously(usingDNAprimase,polymeraseIII,polymeraseI)
o Laggingstrand:strandattheoppositeendofthereplicationfork.Goesfrom3’to5’.
Synthesisoftheleadingstrand
o TostartDNAsynthesis,DNAprimasesynthesizesanRNAprimer
o TheRNAprimeristhenextendedbyDNAPolymeraseIII
o TheRNAprimersareremovedbytheactionofthe5’exonucleaseactivityofDNApolymeraseI,withDNA
synthesizedintheirplaceatthesametime