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