Medical Biochemistry Exam 2 Case Studies and Multiple Choice Questions with complete solutions.

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MEDICAL BIOCHEMISTRY EXAM 2 CASE
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STUDIES
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AND MULTIPLE CHOICE x x




QUESTIONS WITH
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2,4- xDinitrophenol x(DNP), xan xuncoupled xof xoxidative xphosphorylation, xwas xused xas xa
xweight-loss xagent xin xthe x1930s. xReports xof xfatal xoverdoses xled xto xit's xdiscontinuation

xin x1939. xWhich xof xthe xfollowing xwould xmost xlikely xbe xtrue xconcerning xindividuals

xtaking x2,4DNP? x- xcorrect xanswers.ANSWER: xBody xtemperature xis xelevated xas xa

xresult xof xhypermetabolism. xEXPLANATION: xThis xis xbecause xsince xATP xsynthesis xis

xinhibited xby xthis xuncoupler, xthe xenergy xfrom xthe xproton xgradient xcreated xby xthe

xelectron xtransport xchain xhas xto xgo xsomewhere, xso xit xis xeliminated xthrough xthe xbody

xas xheat. x
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Which xof xthe xfollowing xhas xthe xstrongest xtendency xto xgain xelectrons? x- xcorrect
xanswers.ANSWER: xOxygen. xEXPLANATION: xO2 xhas xthe xstrongest xaffinity xto xgain

xelectrons xas xit xis xthe xterminal xacceptor xin xthe xelectron xtransport xchain xand xhas xthe

xmost xpositive xreduction xpotential x(Eo) x
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Explain xwhy xand xhow xthe xmalate-aspartate xshuttle xmoves xnicotinamide xadenine
xdenuclearize xreducing xequivalents xfrom xthe xcytoskeleton xto xthe xmitochondrial xmatrix.

x- xcorrect xanswers.Margaret's xanswer: xthe xmalate-aspartate xshuttle xis xa xpart xof xthe

xmitochondrial xtransport xsystem. xNADH xfrom xthe xcytosol xis xoxidized xto xNAD+ xand

xoxaloacetate xis xreduced xto xmalate. xMalate xis xthen xtransported xacross xthe xinner

xmitochondrial xmembrane xby xthe xshuttle xwhere xit xis xoxidized xback xto xOAA xand

xNAD+ xis xreduced xto xNADH. xThis xis xdue xto xthe xfact xthat xthere xis xno xtransporter xfor

xNADH xacross xthe xinner xmitochondrial xmembrane. xThe xNADH xproduced xby xthis

xshuttle xcan xbe xoxidized xby xcomplex x1 xof xETC, xaka xNADH xdehydrogenase xand

xgenerates x3 xATP. xThis xwhole xprocess xis xunidirectional xand xcosts xno xATP. x
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, Carbon xmonoxide x(CO) xbinds xto xand xinhibits xcomplex xIV xof xthe xETC. xWhat xeffect, xif
xany, xshould xthis xrespiratory xinhibitor xhave xon xphosphorylation xof xadenosine

xdiphosphate xto xadenosine xtriphosphate? x- xcorrect xanswers.Margaret's xanswer: xSince

xcomplex xIV xof xETC xis xbeing xinhibited, xthat xmeans xthat xthere xis xno xway xto xmaintain

xthe xproton xgradient, xmeaning xthere xis xno xenergy xin xorder xto xphosphorylate xADP xto

xATP. xAs xa xreminder, xcomplexes xI xand xIV xare xproton xpumping xsites. x
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Which xof xthe xfollowing xstatements xbest xdescribes xglucose? x- xcorrect xanswers.It xis xa
xC-4 xepimer xof xgalactose. xThis xis xbecause xgalactose xand xglucose xonly xdiffer xin

xconfiguration xaround xcarbon x4 xand xare xinterconvertible xif xyou xuse xan xepimerase.

xGlucose xis xa xPYROSE xring xin xsolution. x
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A xyoung xman xentered xhis xphysician's xoffice xcomplaining xof xbloating xand xdiarrhea.
xHis xeyes xwere xsunken, xand xthe xphysician xnoted xadditional xsigns xof xdehydration. xHis

xeyes xwere xsunken, xand xthe xphysician xnoted xadditional xsigns xof xdehydration. xThe

xpatient's xtemperature xwas xnormal. xHe xexplained xthat xthe xepisode xhad xoccurred

xfollowing xa xbirthday xparty xin xwhich xhe xhad xparticipated xin xan xice-cream xeating

xcontest. xthe xpatient xreported xprior xepisodes xof xa xsimilar xnature xfollowing xthe

xingestion xof xa xsignificant xamount xof xdairy xproducts. xThis xclinical xpicture xis xmost

xlikely xdue xto xa xdeficiency xin xthe xactivity xof: x- xcorrect xanswers.Lactase, xas xthe

xphysical xsymptoms xsuggest xa xdeficiency xin xthe xenzyme xresponsible xfor

xcarbohydrate xdegradation. xThe xfact xthat xit xis xdairy xproducts xshow xthat xthe xenzyme

xis xmost xlikely xdeficient xin xlactase. x
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Routine xexamination xof xthe xurine xof xan xasymptomatic xpediatric xpatient xshowed xa
xpositive xreaction xwith xClinitest x(a xcopper xreduction xmethod xof xdetecting xreducing

xsugars) xbut xa xnegative xreaction xwith xthe xglucose xoxidase xtest xfor xdetecting xglucose.

xUsing xthis xdat, xwhich xsugars xcould xbe xpresent xin xthe xurine xof xthis xindividual? x-

xcorrect xanswers.Fructose, xgalactose, xlactose, xand xxylulose xcould xall xbe xpresent xin

xthe xurine xof xthis xpatient, xAKA xnot xsucrose xor xglucose. xClinitiest xis xa xnonspecific xtest

xthat xproduces xa xchange xin xcolor xif xurine xis xpositive xfor xreducing xsugars x(all

xincluding xglucose xbut xnot xsucrose). xGlucose xoxidase xtest xwill xdetect xonly xglucose

xand xno xother xsugars. xThe xnegative xglucose xoxidase xtest xand xa xpositive xreducing

xsugar xtest xmeans xthat xglucose xcannot xbe xthe xreducing xsugar xin xthe xurine. x
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1) xWhich xone xof xthe xfollowing xstatements xconcerning xgluconeogenesis xis xcorrect? x-
xcorrect xanswers.It xis ximportant xin xmaintaining xblood xglucose xduring xa x2-day xfast.

xDuring xa x2-day xfast, xglycogen xstores xare xdepleted xand xgluconeogenesis xmaintains

xblood xglucose. xThis xis xan xend xergo xif,, xaka xenergy-requiring xpathway xthat xoccurs

xprimarily xin xthe xliver, xwith xthe xkidneys xbecoming xmajor xglucose xproducers xin

xprolonged xfasting. xSince xthis xis xan xend xergo xif xprocess, xboth xATP xand xGTP xget

xhydrolyzed. x
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Which xreaction xin xthe xdiagram xbelow x(pg. x124) xwould xbe xinhibited xin xthe xpresence
xof xlarge xamounts xof xavid xin, xan xegg xwhite xprotein xthat xbinds xand xsequesters xbiotin?

x- xcorrect xanswers.The xcorrect xanswer xis xthe xrxn xof xpyruvate xbeing xconverted xto