ACS BIOCHEMISTRY EXAM QUESTIONS
AND CORRECT VERIFIED ANSWERS
Henderson-HasselbachA2EquationA2-A2Ans--pHA2=A2pKaA2+A2logA2([A-]A2/A2[HA])
FMOCA2ChemicalA2SynthesisA2-A2Ans--
UsedA2inA2synthesisA2ofA2aA2growingA2aminoA2acidA2chainA2toA2aA2polystyreneA2bead.A2FM
OCA2isA2usedA2asA2aA2protectingA2groupA2onA2theA2N-terminus.
SaltingA2OutA2(Purification)A2-A2Ans--
ChangesA2solubleA2proteinA2toA2solidA2precipitate.A2ProteinA2precipitatesA2whenA2theA2cha
rgesA2onA2theA2proteinA2matchA2theA2chargesA2inA2theA2solution.
Size-ExclusionA2ChromatographyA2-A2Ans--
SeparatesA2sampleA2basedA2onA2sizeA2withA2smallerA2moleculesA2elutingA2later.
Ion-ExchangeA2ChromatographyA2-A2Ans--
SeparatesA2sampleA2basedA2onA2charge.A2CMA2attractsA2+,A2DEAEA2attractsA2-.A2MayA2ha
veA2repulsionA2effectA2onA2likeA2charges.A2SaltA2orA2acidA2usedA2toA2removeA2stuckA2protei
ns.
Hydrophobic/ReverseA2PhaseA2ChromatographyA2-A2Ans--
BeadsA2areA2coatedA2withA2aA2carbonA2chain.A2HydrophobicA2proteinsA2stickA2better.A2Elut
eA2withA2non-H-bondingA2solventA2(acetonitrile).
AffinityA2ChromatographyA2-A2Ans--
AttachA2aA2ligandA2thatA2bindsA2aA2proteinA2toA2aA2bead.A2EluteA2withA2harshA2chemicalsA2
orA2similarA2ligand.
SDS-PAGEA2-A2Ans--UsesA2SDS.A2GelA2isA2madeA2fromA2cross-
linkedA2polyacrylamide.A2SeparatesA2basedA2offA2ofA2massA2withA2smallerA2moleculesA2m
ovingA2faster.A2VisualizedA2withA2CoomassieA2blue.
SDSA2-A2Ans--
SodiumA2dodecylA2sulfate.A2UnfoldsA2proteinsA2andA2givesA2themA2uniformA2negativeA2ch
arge.
IsoelectricA2FocusingA2-A2Ans--
VariationA2ofA2gelA2electrophoresisA2whereA2proteinA2chargeA2matters.A2InvolvesA2electrod
esA2andA2pHA2gradient.A2ProteinA2stopsA2atA2theirA2pIA2whenA2neutral.
FDNBA2(1-fluoro-2,3-dinitrobenzene)A2-A2Ans--FDNBA2reactsA2withA2theA2N-
terminusA2ofA2theA2proteinA2toA2produceA2aA22,4-
,dinitrophenolA2derivativeA2thatA2labelsA2theA2firstA2residue.A2CanA2repeatA2hydrolysisA2toA2
determineA2sequentialA2aminoA2acids.
DTTA2(dithiothreitol)A2-A2Ans--ReducesA2disulfideA2bonds.
IodoacetateA2-A2Ans--AddsA2carboxymethylA2groupA2onA2freeA2-
SHA2groups.A2BlocksA2disulfideA2bonding.
HomologsA2-A2Ans--SharesA225%A2identityA2withA2anotherA2gene
OrthologsA2-A2Ans--SimilarA2genesA2inA2differentA2organisms
ParalogsA2-A2Ans--SimilarA2"paired"A2genesA2inA2theA2sameA2organism
RamachandranA2PlotA2-A2Ans--ShowsA2favorableA2phi-
psiA2angleA2combinations.A23A2mainA2"wells"A2forA2α-helices,A2ß-sheets,A2andA2left-
handedA2α-helices.
GlycineA2RamachandranA2PlotA2-A2Ans--
GlycineA2canA2adoptA2moreA2angles.A2(H'sA2forA2R-group).
ProlineA2RamachandranA2PlotA2-A2Ans--
ProlineA2adoptsA2fewerA2angles.A2AminoA2groupA2isA2incorporatedA2intoA2aA2ring.
α-helicesA2-A2Ans--AlaA2isA2common,A2GlyA2&A2ProA2areA2notA2veryA2common.A2Side-
chainA2interactionsA2everyA23A2orA24A2residues.A2TurnsA2onceA2everyA23.6A2residues.A2Dist
anceA2betweenA2backbonesA2isA25.4Å.
HelixA2DipoleA2-A2Ans--
FormedA2fromA2addedA2dipoleA2momentsA2ofA2allA2hydrogenA2bondsA2inA2anA2α-helix.A2N-
terminusA2isA2δ+A2andA2C-terminusA2isA2δ-.
ß-sheetA2-A2Ans--EitherA2parallelA2orA2anti-
parallel.A2OftenA2twistedA2toA2increaseA2strength.
Anti-parallelA2ß-sheetA2-A2Ans--AlternatingA2sheetA2directionsA2(CA2&A2N-
terminiA2don'tA2line-up).A2HasA2straightA2H-bonds.
ParallelA2ß-sheetA2-A2Ans--SameA2sheetA2directionsA2(CA2&A2N-
terminiA2lineA2up).A2HasA2angledA2H-bonds.
ß-turnsA2-A2Ans--TightA2u-turnsA2withA2specificA2phi-
psiA2angles.A2MustA2haveA2glyA2atA2positionA23.A2ProlineA2mayA2alsoA2beA2atA2ß-
turnA2becauseA2itA2canA2haveA2aA2cis-omegaA2angle.
, LoopsA2-A2Ans--
NotA2highlyA2structured.A2NotA2necessaryA2highlyA2flexible,A2butA2canA2occasionallyA2mov
e.A2VeryA2variableA2inA2sequence.
CircularA2DichroismA2-A2Ans--
UsesA2UVA2lightA2toA2measureA22°A2structure.A2CanA2beA2usedA2toA2measureA2destabilizati
on.
Disulfide-bondsA2-A2Ans--BondsA2betweenA2twoA2-
SHA2groupsA2thatA2formA2betweenA22°A2andA23°A2structure.
ß-mercaptoethanolA2-A2Ans--BreaksA2disulfideA2bonds.
α-keratinA2-A2Ans--formedA2fromA22A2α-
helicesA2twistedA2aroundA2eachA2other.A2"CoiledA2coil".A2Cross-
linkedA2byA2disulfideA2bonds.
CollagenA2-A2Ans--RepeatingA2sequenceA2ofA2Gly-X-
Pro.A23A2strandedA2"coiledA2coil".A2ContainsA2glyA2core.
MyoglobinA24°A2StructureA2-A2Ans--SymmetricA2homodimer,
HemoglobinA24°A2StructureA2-A2Ans--Tetramer.A2DimerA2ofA2dimers.A2α2ß2A2tetramer.
α/ßA2ProteinA2FoldingA2-A2Ans--LessA2distinctA2areasA2ofA2αA2andA2ßA2folding.
α+ßA2ProteinA2FoldingA2-A2Ans--TwoA2distinctA2areasA2ofA2αA2andA2ßA2folding.
MechanismA2ofA2DenaturantsA2-A2Ans--HighlyA2soluble,A2H-
bindingA2molecules.A2StabilizeA2proteinA2backboneA2inA2water.A2AllowsA2denaturedA2state
A2toA2beA2stabilized.
TemperatureA2DenaturationA2ofA2ProteinA2-A2Ans--MidpointA2ofA2reactionA2isA2Tm.
CooperativeA2ProteinA2FoldingA2-A2Ans--FoldingA2transitionA2isA2sharp.A2MoreA2reversible.
FoldingA2FunnelA2-A2Ans--
ShowsA23DA2versionA2ofA22DA2energyA2states.A2LowestA2energyA2isA2stableA2protein.A2Rou
ghA2funnelA2isA2lessA2cooperative.
Protein-ProteinA2InterfacesA2-
A2Ans--"Core"A2andA2"fringe"A2ofA2theA2interfaces.A2CoreA2isA2moreA2hydrophobicA2andA2isA
2onA2theA2insideA2whenA2interfaced.A2FringeA2isA2moreA2hydrophilic.
AND CORRECT VERIFIED ANSWERS
Henderson-HasselbachA2EquationA2-A2Ans--pHA2=A2pKaA2+A2logA2([A-]A2/A2[HA])
FMOCA2ChemicalA2SynthesisA2-A2Ans--
UsedA2inA2synthesisA2ofA2aA2growingA2aminoA2acidA2chainA2toA2aA2polystyreneA2bead.A2FM
OCA2isA2usedA2asA2aA2protectingA2groupA2onA2theA2N-terminus.
SaltingA2OutA2(Purification)A2-A2Ans--
ChangesA2solubleA2proteinA2toA2solidA2precipitate.A2ProteinA2precipitatesA2whenA2theA2cha
rgesA2onA2theA2proteinA2matchA2theA2chargesA2inA2theA2solution.
Size-ExclusionA2ChromatographyA2-A2Ans--
SeparatesA2sampleA2basedA2onA2sizeA2withA2smallerA2moleculesA2elutingA2later.
Ion-ExchangeA2ChromatographyA2-A2Ans--
SeparatesA2sampleA2basedA2onA2charge.A2CMA2attractsA2+,A2DEAEA2attractsA2-.A2MayA2ha
veA2repulsionA2effectA2onA2likeA2charges.A2SaltA2orA2acidA2usedA2toA2removeA2stuckA2protei
ns.
Hydrophobic/ReverseA2PhaseA2ChromatographyA2-A2Ans--
BeadsA2areA2coatedA2withA2aA2carbonA2chain.A2HydrophobicA2proteinsA2stickA2better.A2Elut
eA2withA2non-H-bondingA2solventA2(acetonitrile).
AffinityA2ChromatographyA2-A2Ans--
AttachA2aA2ligandA2thatA2bindsA2aA2proteinA2toA2aA2bead.A2EluteA2withA2harshA2chemicalsA2
orA2similarA2ligand.
SDS-PAGEA2-A2Ans--UsesA2SDS.A2GelA2isA2madeA2fromA2cross-
linkedA2polyacrylamide.A2SeparatesA2basedA2offA2ofA2massA2withA2smallerA2moleculesA2m
ovingA2faster.A2VisualizedA2withA2CoomassieA2blue.
SDSA2-A2Ans--
SodiumA2dodecylA2sulfate.A2UnfoldsA2proteinsA2andA2givesA2themA2uniformA2negativeA2ch
arge.
IsoelectricA2FocusingA2-A2Ans--
VariationA2ofA2gelA2electrophoresisA2whereA2proteinA2chargeA2matters.A2InvolvesA2electrod
esA2andA2pHA2gradient.A2ProteinA2stopsA2atA2theirA2pIA2whenA2neutral.
FDNBA2(1-fluoro-2,3-dinitrobenzene)A2-A2Ans--FDNBA2reactsA2withA2theA2N-
terminusA2ofA2theA2proteinA2toA2produceA2aA22,4-
,dinitrophenolA2derivativeA2thatA2labelsA2theA2firstA2residue.A2CanA2repeatA2hydrolysisA2toA2
determineA2sequentialA2aminoA2acids.
DTTA2(dithiothreitol)A2-A2Ans--ReducesA2disulfideA2bonds.
IodoacetateA2-A2Ans--AddsA2carboxymethylA2groupA2onA2freeA2-
SHA2groups.A2BlocksA2disulfideA2bonding.
HomologsA2-A2Ans--SharesA225%A2identityA2withA2anotherA2gene
OrthologsA2-A2Ans--SimilarA2genesA2inA2differentA2organisms
ParalogsA2-A2Ans--SimilarA2"paired"A2genesA2inA2theA2sameA2organism
RamachandranA2PlotA2-A2Ans--ShowsA2favorableA2phi-
psiA2angleA2combinations.A23A2mainA2"wells"A2forA2α-helices,A2ß-sheets,A2andA2left-
handedA2α-helices.
GlycineA2RamachandranA2PlotA2-A2Ans--
GlycineA2canA2adoptA2moreA2angles.A2(H'sA2forA2R-group).
ProlineA2RamachandranA2PlotA2-A2Ans--
ProlineA2adoptsA2fewerA2angles.A2AminoA2groupA2isA2incorporatedA2intoA2aA2ring.
α-helicesA2-A2Ans--AlaA2isA2common,A2GlyA2&A2ProA2areA2notA2veryA2common.A2Side-
chainA2interactionsA2everyA23A2orA24A2residues.A2TurnsA2onceA2everyA23.6A2residues.A2Dist
anceA2betweenA2backbonesA2isA25.4Å.
HelixA2DipoleA2-A2Ans--
FormedA2fromA2addedA2dipoleA2momentsA2ofA2allA2hydrogenA2bondsA2inA2anA2α-helix.A2N-
terminusA2isA2δ+A2andA2C-terminusA2isA2δ-.
ß-sheetA2-A2Ans--EitherA2parallelA2orA2anti-
parallel.A2OftenA2twistedA2toA2increaseA2strength.
Anti-parallelA2ß-sheetA2-A2Ans--AlternatingA2sheetA2directionsA2(CA2&A2N-
terminiA2don'tA2line-up).A2HasA2straightA2H-bonds.
ParallelA2ß-sheetA2-A2Ans--SameA2sheetA2directionsA2(CA2&A2N-
terminiA2lineA2up).A2HasA2angledA2H-bonds.
ß-turnsA2-A2Ans--TightA2u-turnsA2withA2specificA2phi-
psiA2angles.A2MustA2haveA2glyA2atA2positionA23.A2ProlineA2mayA2alsoA2beA2atA2ß-
turnA2becauseA2itA2canA2haveA2aA2cis-omegaA2angle.
, LoopsA2-A2Ans--
NotA2highlyA2structured.A2NotA2necessaryA2highlyA2flexible,A2butA2canA2occasionallyA2mov
e.A2VeryA2variableA2inA2sequence.
CircularA2DichroismA2-A2Ans--
UsesA2UVA2lightA2toA2measureA22°A2structure.A2CanA2beA2usedA2toA2measureA2destabilizati
on.
Disulfide-bondsA2-A2Ans--BondsA2betweenA2twoA2-
SHA2groupsA2thatA2formA2betweenA22°A2andA23°A2structure.
ß-mercaptoethanolA2-A2Ans--BreaksA2disulfideA2bonds.
α-keratinA2-A2Ans--formedA2fromA22A2α-
helicesA2twistedA2aroundA2eachA2other.A2"CoiledA2coil".A2Cross-
linkedA2byA2disulfideA2bonds.
CollagenA2-A2Ans--RepeatingA2sequenceA2ofA2Gly-X-
Pro.A23A2strandedA2"coiledA2coil".A2ContainsA2glyA2core.
MyoglobinA24°A2StructureA2-A2Ans--SymmetricA2homodimer,
HemoglobinA24°A2StructureA2-A2Ans--Tetramer.A2DimerA2ofA2dimers.A2α2ß2A2tetramer.
α/ßA2ProteinA2FoldingA2-A2Ans--LessA2distinctA2areasA2ofA2αA2andA2ßA2folding.
α+ßA2ProteinA2FoldingA2-A2Ans--TwoA2distinctA2areasA2ofA2αA2andA2ßA2folding.
MechanismA2ofA2DenaturantsA2-A2Ans--HighlyA2soluble,A2H-
bindingA2molecules.A2StabilizeA2proteinA2backboneA2inA2water.A2AllowsA2denaturedA2state
A2toA2beA2stabilized.
TemperatureA2DenaturationA2ofA2ProteinA2-A2Ans--MidpointA2ofA2reactionA2isA2Tm.
CooperativeA2ProteinA2FoldingA2-A2Ans--FoldingA2transitionA2isA2sharp.A2MoreA2reversible.
FoldingA2FunnelA2-A2Ans--
ShowsA23DA2versionA2ofA22DA2energyA2states.A2LowestA2energyA2isA2stableA2protein.A2Rou
ghA2funnelA2isA2lessA2cooperative.
Protein-ProteinA2InterfacesA2-
A2Ans--"Core"A2andA2"fringe"A2ofA2theA2interfaces.A2CoreA2isA2moreA2hydrophobicA2andA2isA
2onA2theA2insideA2whenA2interfaced.A2FringeA2isA2moreA2hydrophilic.
