Note:thistimetherealexamwillbedifferenttoa

substantialextentfromthispracticeexam.However,
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deviatingsignificantlyfromthispracticeexam.

Chem109C2stInClassExam
Nov.5th,2010
PracticeExam

Name:________________________

Permnumber:_________________

Name:____________________________________Permnumber:__________________
Question
1)multiplechoices(50pts)
2)reactions(12pts)
3)shortanswerquestions(33pts)
Total(90pts)

Yourscore

1.MULTIPLECHOICE.Choosetheonealternativethatbestcompletesthestatementoranswersthequestion(50pts)
1)Howdoenzymesdifferfromnonbiologicalcatalysts?
1)_______
A)TheyrequirelowerpHtobefunctional.
B)Theyrequirehigherpressuretobefunctional.
C)Theyaremorepolarthannonbiologicalcatalysts.
D)Theyhavespecificityforthesubstrate.
E)Theyhavelowermolecularweightsthannonbiologicalcatalysts.

2)Whichofthefollowingcoenzymesisrequiredfortheenzymecatalyzedreactionshownbelow?
2)_______

transketolase
Xylose-5-P+Ribose-5-P

Glyceraldehyde-3-P+Sedoheptulose-7-P
A)NADH
B)NADPH
C)PLC
D)THF
E)TPP

3)Whichofthefollowingvitaminsareradicalinhibitorsorantioxidants?
3)_______
A)vitaminsB2andB6
B)vitaminsCandE
C)niacin
D)vitaminsAandD
E)vitaminsB1andB12

4)Whichofthefollowingsetsofparametersareallalteredwhenareactioniscarriedoutinthe
presenceofacatalyst?
A)G,H,Keq

4)_______

B)H,S,krate
C)Ea,freeenergyofactivation,krate
D)G,krate,Keq
E)H,DS,Ea

5)Whichofthefollowingisnottrueabouttheenzymealdolase?
A)Theenzymeiscalledaldolasebecausethereversereactionisanaldolcondensation.
B)Itcatalyzesthecleavageofasixcarboncompoundintotwothreecarboncompounds.
C)ItcatalyzesthecleavageofD-fructose1,6-diphosphateintoglyceraldehyde-3-phosphate
anddihydroxyacetonephosphate.
D)ItcatalyzesthecleavageofD-galactoseintotwomoleculeseachcontaining3-carbons.
E)Itusesalysinesidechainaminogrouptoformaniminewiththesubstrateattheactive
site.

6)Whichofthefollowingresiduesarefoundattheactivesiteoflysozyme?
A)His57,Asp102

5)_______

6)_______

B)His57,Asp52
C)Glu35,His57
D)Asp102,Glu35
E)Glu35,Asp52

7)Aquinoneispartofthestructureofvitamin__________.
A)B12
B)K
C)C

7)_______
D)B1

E)B2

8)Whichofthefollowingarerequiredspeciesforbiotin-requiringenzymes?
A)Mg+2
B)HCO3-

8)_______

C)ATP
D)AandB
E)A,BandC

9)Whichofthefollowingisthebestdefinitionofacatalyst?
A)Itincreasestherateofachemicalreaction.
B)Itdecreasestherateofareaction.
C)Itdecreasesactivationenergy.
D)Itincreasesactivationenergy.
E)AandC

10)Generallyspeaking,whichofthefollowingoxidation-reductionreactionsutilizeNAD+and
NADP+asoxidationcoenzymes?

9)_______

10)______

A)alcoholsoxidizedtocarboxylicacids
B)alcoholsoxidizedtoaldehydes
C)alcoholsoxidizedtoketones
D)AandB
E)A,B,andC

11)Whichofthefollowingisnotneededforthepyruvatedehydrogenasesystem?
A)NAD+

11)______

B)biotin
C)lipoate
D)coenzymeA
E)FAD

12)Atwhatpositionofthepyridineringinthecoenzymebelowwilloxidation-reductionreactions
takeplace?

12)______

A)1

B)2

C)3

D)4

E)5

13)Whatdoesthemodeltermedlock-and-keystandfor?
A)TheN-terminalandtheC-terminalendsofaproteinfiteachotherlikeakeyfitsalock.
B)Thenonpolarsitesofproteinsfiteachotherlikeakeyfitsalock.
C)Thehydrogenbondsinthe-helixfiteachotherlikeakeyfitsalock.

13)______

D)Thesubstratefitstheactivesiteoftheenzymelikeakeyfitsalock.
E)Theaminoacidsinapeptidechainfiteachotherlikeakeyfitsalock.

14)Whichofthefollowingstatementsbestdescribeswhatcofactorsare?
A)Theyareorganicmoleculesderivedfromcompoundscommonlyknownasvitamins.
B)Theyareorganicmoleculescalledcoenzymes.
C)Theyareorganicmoleculesthatassistenzymesincarryingouttheircatalyticreactions.
D)Theyaremetalionsthatassistenzymesincarryingouttheircatalyticreactions.
E)alloftheabove

15)Whichofthefollowingstatementsisnottrueofcoenzymes?
A)Coenzymescatalyzechemicalreactionssimilartoenzymes.
B)Coenzymesmayfunctionasoxidizingandreducingagents.
C)Coenzymesplayavarietyofchemicalrolesexactlylikethoseplayedbytheaminoacidside
chainsofenzymes.
D)Coenzymesmayfunctionasnucleophilesorstrongbasesneededinareaction.
E)Coenzymesmayfunctionasactivatorsneededinareaction.

16)Whichofthefollowingis/aretrueaboutbase-catalysts?
A)Theyfacilitatetheformationofanegativelychargedtetrahedralintermediate.
B)Theyincreasetherateofareactionbyremovingaprotonfromareactant.
C)Theyincreasetherateofareactionbyprovidingapathwaywithamorestabletransition
state.
D)AandBonly
E)A,BandC

17)Whichofthefollowingrepresentsthefirststep(s)inthemechanisminvolvinggeneral-base
catalysisforthereactionshownbelow?

A)I

B)II

C)III

D)IV

E)V

14)______

15)______

16)______

17)______


18)WhataretheproductsobtainedfromthereactionofNADHwithFMNcatalyzedbyNADH
dehydrogenaseasshownbelow?

NADH
NADH+FMN
A)NAF+DHN
B)N2A2D2+FMNH2
C)NAD++FMNH2

18)______

?+?

D)NAF+DNH2
E)NAD++FMNH

19)Whichofthefollowingis/arewater-solublevitamins?
A)thiamine(vitaminB1)

19)______

B)pyridoxine(vitaminB6)
C)vitaminB12
D)riboflavin(vitaminB2)
E)alloftheabove

20)Whichofthefollowingstatementsis/aretrueaboutcatalysts?
A)Theyparticipateinthechemicalreaction,butarenotchangedorconsumed.
B)Theychangetheamountofproductformedinachemicalreaction.
C)Theycanbeusedonlyonce.
D)Theychangethestabilityofreactantsandproducts.
E)alloftheabove

21)Whichofthefollowingisnottrueaboutmetal-ioncatalysts?
A)Theycanmakealeavinggroupaweakerbaseandthereforeabetterleavinggroup.
B)Theycanmakeareactioncentermoresusceptibletoreceivingelectronsandstabilizea
developingchargeonthetransitionstate.
C)TheyactasLewisbases.
D)Theycoordinatewithatomswithnonbondedelectrons.
E)Theycanincreasetheelectrophilicityofareactioncenter.

22)WhichofthefollowingvitaminscatalyzesacyltransferreactionsandrequiresCoASHasa
coenzyme?
A)panthothenate
B)niacin
C)lipoate
D)thiamine
E)vitaminB12

23)Whichofthefollowingresiduesactsasageneral-acidcatalystinaldolasebutasageneral-base
catalystinchymotrypsin?
A)lysine
B)histidine
C)asparagine
D)cysteine
E)methionine

20)______

21)______

22)______

23)______


24)Apuresampleofthetrans-2-bromocyclopentanolenantiomershownbelowreactswithHCl.
Thereactionproceedsbywayofabromoniumion.Whatis/aretheproduct(s)ofthereaction?

24)______

A)IandIII

B)IIonly

C)Ionly
D)IIandIV

25)Whichofthefollowingisastepinthemechanismofthereactionshownbelow?

A)I

1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)

D
E
B
C
D
E
B
E
E
E
B
D
D

B)II

C)III

D)IV

E)V

25)______

14) E
15) C
16) E
17) A
18) C
19) E
20) A
21) C
22) A
23) B
24) A
25) B

2.Pleasewritedownthecoenzymesderivedfromthespecifiedvitaminsandthereactiontypetheycatalyzes(12pts).

corestructure/
reactingunit

Vitamine

coenzyme(s)
pleaselistallpossible

reactioncatalyzed

NAD+,NADH
NADP+,NADPH

reduction
oxidation

coenzymeB12

isomerization

biotin

carboxylation

pyridoxalphosphate(PLP)

decarboxylation
transamination
racemization
CCbondcleavage
,elimination
substitution

B3

B12
O

HN

NH

B6

OH

3.Foreachofthefollowingenzymecatalyzedreactions,filltheemptyboxesasindicated(16pts).

1)

3)

4)

2)

4.Brieflyanswerthefollowingquestions(12pts).
1)Aldolasecatalyzesthefollowingreaction,pleaseprovideareasonablemechanismtoexplainhowitoccursintheactive
site(note:youdonothavetodrawtheactivesite,insteadyoucanusethesidechainfunctionalgroupstopromotethe
reaction).

(seepage1093)

2)TherateofthefollowingreactionismuchfasterthanthesubstratewiththeNreplacedwithacarbon.Pleaseproposea
mechanismtoexplain.

HO

Cl

OH-, H2O

N Me
N Me

HO
Cl

HO
HO

HO
Cl
N Me
N Me

N Me
Cl
HOCl

Cl

3)Dehydrataseisapyridoxalrequiringenzymethatcatalyzesan,eliminationreaction.Proposeamechanismforthis
reaction.

O
O

hydrolysis
dehydratase

HO

PLP

NH3

NH4+

O
O

E
N

transimination
PiO

B:H

NH2

B-H

HO

HO

O
N

PiO
N
H

H
O

O
O

N
PiO
N
H

H
O

H2O

O
N
PiO
N
H

H
O

O
NH

E-(CH2)4NH2

H
O

N
H

E-(CH2)4NH2

tautomerization