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ProteinsandNucleicAcidsSept.14,2017
ProteinFunction
Proteinfunction
•Structure=cytoskeleton,connectivetissues• Transport=ionchannels(Na+,K+),nerveimpulses
•Cellsignaling=insulin,antibodies,communicationinbody
•Regulation =enzymes
DailyLives… Hair,antibodies,spiderwebs,eggwhites,tofu
Proteinsaremadeupof…
•Aminoacids•2primaryfunctionalgroupswithcentralcarboninthemiddle•20aminoacids•8areessential,cannotmakeinourbodies
Sidechains
4types:1.Polar(hydrophilic)
2.Nonpolar(hydrophobic)3.Acidic(negative)4.Basic(positive)
Howareaminoacidslinkedtogether?
Dehydrationsynthesis
1. CarboxylgroupwillinteractwithAminogroup
2. OxygenandtwoHydrogensformwater
3. Carbonneedsbondtosomethingà N
4. Peptidebond
PeptideBond=AmideBond(Amidefunctionalgroup)
Structuredictatesfunction?
SickleCellDisease
• Abnormalhemoglobin(hemoglobinS) intheirredbloodcells• Cancauseblockage• Deprivationofoxygen
Proteinscanbe…
•Roughlylinearinshape(strands/sheets)•Rounded/sphericalinshape(globularprotein)
Stagesofproteinformation
1.Primary – sequence2.Secondary – alpha-helixorbeta-pleated
3.Tertiary – 3Dstructure4.Quaternary – twoormore(notall
proteins)
PrimaryStructure
•Theuniquesequenceofaminoacidsinapolypeptidechain•Governedbynucleotidesequence(DNA)
Structure
Thesequenceofaminoacidsdeterminesapolypeptidesthree-dimensionalconformationà itsfunctionalcharacteristics
N- andC-terminus/Residue
Secondarystructure
•Coilsandfoldsinapolypeptidechaincausedbyhydrogenbondsbetweencarboxylandaminogroups
2Types
•Alpha-helix•Helicalshape
•Beta-pleated•Chainslieparallel
TertiaryStructure
•Supercoilingofapolypeptidethatisstabilizedbyside-chaininteractions
StabilizedbyR-groupinteractions
Attractionandrepulsionforces,andtheprotein’senvironment,forcesittoundergoadditionalfolding
1. Hydrogenbonds – polarsidechains2. Ionicbonds– oppositelychargedsidechains
3. VanderWaals – nonpolarRgroups4. Proline– Rgroupattachestotheaminoacidà Kink
5. Cysteine– cysteineresiduesformstrongdisulfidebridgeinteractions6. Hydrophobic/hydrophilicinteractions
QuaternaryStructure
•Whenaproteinismadeupoftwoormoretertiarypolypeptides
Denaturation
Achangeinthethree-dimensionalshapeofaproteincausedbychangesintemperature,pH,ionicconcentration,orotherenvironmentalfactors
Think:Howwilldenaturingaproteinaffectit’sfunction?
NucleicAcids
Whatarenucleicacids?
•Nucleicacidsareinformationalmacromolecules•Usedbyallorganismstostorehereditaryinformationthatdeterminesstructuralandfunctionalcharacteristics
2Types/Whatdotheydo?
1. DNA(deoxyribonucleicacid) =storestheinstructionsforcreatinganorganisms
2. RNA(ribonucleicacid) =readstheinformationinDNAandtransportstototheprotein-buildingapparatusinthecell
Whatarenucleicacidsmadeof?
Nucleotides =subunit(monomer)ofDNAandRNA1. Nitrogenousbase2. 5-carbonsugar3. Phosphategroup
DNAandRNA5-carbonsugar
5nitrogenousbases
Pyrimidine(singlering)•Thymine/uracil•Cytosine
Purines(double-ring)•Adenine•Guanine
Structure
Strand =seriesofnucleotideslinkedtogetherforminganucleotidepolymer
•RNAcoilsintoahelix,butsinglestranded•DNAalsohelical,butcomposedoftwostrands
Howarestrandscreated?
Dehydrationsynthesis•Covalentbondbetweenphosphate groupofonenucleotideandhydroxyl groupattachedtocarbon-3ofthesugaronanothernucleotide•CreatesaPhosphodiesterbond
HowaretwoDNAstrandsheldtogether?
• Heldtogetherbyhydrogenbondsbetweennitrogenousbasesonadjacentstrands• DNAstrandsareantiparallel=twoadjacentnucleotidepolymersrunninginoppositedirectionstooneanother
Hydrogenbond
Notrequiredforquizà Energyintermediates
Nucleotidesarealso usedtomakeimportantintermediatesinacell’senergytransformation
• ATP(adenosinetriphosphate)a=usedtodrivevirtuallyallenergy-requiringreactionsinacell• NAD+andFAD=ATPderivativesusedintheproductionofATP• NADP+=coenzymeinphotosynthesis
QuickCheck
Whycanaproteinbecalledapolypeptide,butapolypeptidecannotbecalledaprotein?
Howisthe3-dimensionalshapeofproteinsformed?
Howisapeptidebondformedbetweentwoaminoacids?
Namethreefunctionsofproteinsinalivingorganisms.
Whichelementisfoundinnucleicacids,butneitherincarbohydratesnorproteins?
Whatdoesanucleotideconsistof?
DifferentiatebetweenDNAandRNA.
WhattypeofbondsholdthenitrogenousbasesofDNAtogether?
TextbookProblems
ProteinsPg.50#19,20,21,22,23,24,25,26
NucleicAcidPg.56#18,19