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Chemistry 333 Principles of Biochemistry

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Chemistry 333 Principles of Biochemistry Chemistry333 Principlesof Biochemistry Fall2009 SecondExam October29, 2009 NAME: f,to5E vo rfl/lF ,Y tQfrr, ffcnHffiSt 1. / 6 points 2. ! $ points 3. 12points 4. ! 18 points 5. l6 points 6. 14 points 7. I 6 points ! 14 points 9. 124points 10. / 2 points (EXTRACREDIT) TOTAL: /100points 1. cl-D-mannoseis a sweet-tastingsugar. B-D-mannose,on the other hand, tastes bitter. A pure solution of q-D-mannose loses its sweet taste with time as it is converted into the B-anomer. Drawthe a and B anomersof D-mannoseand EXPLAINwith words and/or pictureshow the B-anomeris formedfrom the q-anomer. (6 points) CU>o11 $ \ L'-Q I tL6-'(Pc- tI Ko*-t-t{ K--? -o{+ *flunnop 0-p [ -? -oF{ Lqrp* A. It is a trimercomposed of D-glucose(1't position)and D-mannose(2nd position)and D-galactose(3'd position) B. The linkageis betweenglucose and mannose is B(1) 3). c. The linkagebetween mannose and galactose is o(1 ) 6). D. The anomericcarbon NOT involved in anyof the linkagesis in the B configuration. ClilpoL* LWtr+ 3. Considerthe Michaelis-Mentenplot shownbelow: (12 points) A. Labelthe 2 typesof inhibitorshown by puttingthe type of inhibitorin the box belowthe line.(A is thetop boxand middleline and B is the bottombox and lowestline) B. What effect (increase,decrease, stay the same) does the inhibitordepicted below have on Vr"r. InhibitorA:Sl""4p +*- SqV,"q-- \.(l fnhibitorB: \JZ C^-AA 3"U C. \Mat effect (increase,decrease, stay the same) does the inhibitordepicted below have on Kr. fnhibitorA:In Ll|^p&!5e9 rnhibitorB:S.|""?p Jt* 3a,YW- U Co*ga+r{rue- vi nmol/min Nl.^^ f I \()v\ - (--o {+\Ae- tsl(mM) 4 4. ProteinStructure: (1g points) A. what is meantby the "primarystructure" of a protein? {1 f,, \hA Urc aJ,,-5*1y cthn,a,.noc*J- U 4..I\ B. Wl'tichlevel(s) of proteinstructure depend qnly upd/nydrogenbonding between atomsof the peptidebackbone? kL% Cz4 c. what levelof structureincludes q-helices and B-sheets? (>")f -,-1>@ Sl.-..--!--'a- D' How is the structureof an q-helixh-aintained?(Be SPECIFICabout interactions!) ru€ 5. (6 points) A- \Mat two carbohydratemonomers make up lactose? LWvL 8*"-*<- B. \Mat specific linkagejoins these monomers? C. \My is lactosedigestible to mosthumans? tt)ot^^'--t* QvtlqwL 95 t ,J, I (t \ h."-t-ft" Li\L ltz's bc \.lea-.- 0- 1\\-6\nb ft^.-e1a 6. Which of the followingamino acids would be most likely to be found buriedin the interior of a typical protein, and which would be more Iikely to be found on the protein's surface? Gircle the appropriateanswer in each case. (4 points) Amino acid Probablelocation Phe @ outside Glu inside @ Leu (@ outside Lys inside ryffi U+lr'r+ t t[ 7. (6points) A. Drawthestructureorsucrose. -fr"i _LX:{l <f-'--,-'*-<,p(rd$"^.t-" wc[ o* i B. Definea"reducing sugar." ffifl-,f',r* -) Explainwhy sucr&e glucose G not a reducingsugar, euin.ihough both o o",^- \ andfructose are reducing sugars. t+O l+ - N ' c. reducingsugars are not? a)L q 3+A\r "l^n- 8p^,5 k s\-j.-n'=h+ ,rr\^i.k; }< ,, XcI" $rruL ) e.de:6, r,r\'tU-1-hvd''"!'Ulthld 8. A compoundhas beendeveloped by drug companiesthat inhibitsthe enzymeHIV protease, which is necessaryfor the proper maturationof the virus. The kineticsof the enzymewith and without the proteaseinhibitor saquinavirare shown in the plot below. (14points) I lV, *ecrms enz. .r | 0 '' ltmolesprod. t4s1,M"rx lo{ HIV proteaseis knownto obey Michaelis-Mentenkinetics under the conditions where K'1- 1 mM, % - 167 mmol producUsec/mgenzyme, and the substrate concentrationis 0.5 mM. Calculatethe V'""*of HIV protease. I Vo 7 V*- frl [u+= K,^^+[sJ 0,E +l [,s 2. Vr", S{:^^e 1r,* so.wL \ 3. \Mat typeof inhibitoris saquinavir? 9. MultipleChoice (2 pointseach) (24 points) 1. Amyloseis differentfrom amyolopectinbecause it is A. Composedof glucoseresidues B. lt hasmore glucose residues (yis-,A. highlybranched D. lt is unbranched E. lt containsno threedimensional structure 2. Belowis the structurefor a cyclic D-monosaccharide. Which is the anomericcarbon atom? A. 1 .- r\\ \7 *oE*, p- oII c.3 l,/ \l D.4 ,N+-{ruh,o" OH OI{ E.5 3. An enzymeshows MichaelisMenten Kinetics. What would be the effectof an uncompetitiveinhibitor when analyzedby a Lineweaver-Burk(double reciprocal)plot? A. Vr., woulddecrease, the K, wouldnot change B. Vr., wouldnot change, the K, woulddecrease ,a\ (9r., woulddecrease, the K, woulddecrease D. Vr., wouldnot change, the K, wouldnot change E. V.r, woulddecrease, the K, wouldincrease 4. Which is true aboutthe side chainsof residuesin an a-helix? A. Theypoint toward the centerof the helix. B^They extendabove or belowthe pleats. ,rf: ' lL7ney pointoutward and are perpendicularto the helixaxis. D. Theydo nothydrogen bond with each other. E. Theyhave no effecton the stabilityof the helix. 5. How does an enzyme's K, compare to its affinity for substrate? Thegreater the K.",the higherthe affinity. The lowerthe Kr, the higherthe affinity. C. The relationshipdepends on whetheran inhibitoris presentor not. D. The relationshipdepends on the enzyme'sVr"r. E. The two have nothingto do with one another. 6. In the presence of alcohol dehydrogenase,the rate of reduction of acetaldehydeto ethanol increases as you increase the concentration of acetaldehyde.Eventually the rate of the reaction reaches a maximum, where further increases in the concentration of acetaldehyde have no effect. Why? "rn ( A. |ll of the alcoholdehydrogenase molecules are boundto acetaldehydemolecules \-/ B. at highconcentrations of acetaldehyde,the activationenergy of the reaction decreases C. theenzyme is no longerspecific for acetaldehyde D. at highconcentrations of acetaldehyde,the AGo'of the reactiondecreases E. the enzymeis denatured 7. Whichstatement about enzymecatalyzed reactions is NOTtrue? A. enzymesform complexes with their substrates. B. enzymeslower the activationenergy for chemicalreactions. ,/a\ ( C. /nzymes changethe thermodynamicsof chemicalreactions. \-/ D. manyenzymes change shape slightly when substrate binds E. reactionsoccur at the "activesite" of enzymes,where a precise3D orientationof aminoacids is an importantfeature of catalysis. 8. In the induced fiUtransition state analog model of substrate binding to enzymes, A. the substratechanges its conformationto fit in the activesite the activesite changes its conformationto fit the substrate thereis a conformationalchange in theenzyme and the substratewhen the substratebinds D. thereis aggregationof severalenzyme molecules when the substrate binds E. multiplesubstrates fit intothe activesite at the sametime 9. In glycoproteins,the carbohydratemoiety is always attachedthrough the aminoacids: trp,asn, or cys ,r'nL t B. ) asn,ser or thr rc. g|y,ala or asp D. asnor glu E. gluor arg 10. Which is the Haworthproiection of B-D-tagatose? A. t. cH?oH l- C*O B. il. I ITO_C_H c. ilt. I HO*C-H r^'.- I ( D.) tv. H*C-OH I E. none of the above cl{zoH D-Tqgarose I HOCH" H 1,7-q \l [x s.) u ,L--0* oH g\..JcH"og l,/E \ tl OH OI{ rh[-{/o,o" OH Og rv *o?2o\o" qIIzOrr Kon olr/ H\JcH"oH OH HH l0 11- The pancreasis protectedfrom digestionby trypsin,a proteolyticenzyme that it produces,because A. theenzyme works only on denaturedproteins. B. theenzyme is specificfor plantproteins. c. theenzyme works onry at thesurface of membranes. ,rGa ( D. ) theenzyme is notactivated until it is proteolyticallymodified. \J E. proteinsof the pancreaslack bonds susceptible to cleavageby this enzyme. 12. The V'"' for the substrate to the right in the absence of inhibitor is: 0.5mmol/min 1 mmol/min 2 mmol/min D. 2mM E. 0.5mM lts Ilependencsof enzymsmle v {pmolltnin}as a funcfionaf *uhstrf,te cancentratisn$ fmM). Al*s shown is tfie dependencirof tfre rate in tfie p]lesencsof en inhbitnr, presentat a concentatlsn of Z mM. EXTRACREDIT: (2 points) 1. spellyour professor's last name correcily. (l point) ilrycyNA 2. Translatethe following amino acid sequence into one lettercode to reveala sentence.Write out the sentencewith soacesbetween the words!(1 points) Trp Glu Leulle LysGlu Asp Arg HisArg TyrCys Tyr Asn Ala SerAsp Ala TrpGly Ser. trJaL( re bL 14rycyPASDfr,-AG25 l1.
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