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Exam2 - IICIHEIHIZICIICIT 1'3244 FAii 51247'18135...

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Unformatted text preview: IICIHEIHIZICIICIT 1'3244 FAii 51247'18135 ElIEIEHEl-l IIII'Ii' UT AUSTIN + ELEETHEINIE HESEH I002r’010 EXAM 2 CH 369 October 11, 2007 Name: eID 1-46 1 pt each Choose the one alternative that best completes the statement or answers the question. i. A membrane is impermeable to charged molecules and does not allow passage of ions because of: A) the hydrophilic nature of the membrane D) all of the above B) the thickness of the membrane E) none of the above C) the hydrophobic nature ofthe membrane 2. In unsaturated fatty acids found in biological membranes, the double bond is usually the A) trans configuration 13) ois configuration C) none of the above 3. Amino acids involved in covalent catalysis include all of the following EXCEPT: A) cysteine E) serine C) lysine D) arginine E) histidine 4. In cooperative substrate binding. the velocity versus substrate curve has a(n) A) hyperbolic shape D) positive, linear slope B) negative, linear slope E) none of the above C) sigmoidal shape 5. Which of the following is thermodynamically unfavorable? A) Lateral diffusion B) Transverse diffusion 6. Acid-base catalysis is the partial transfer of a proton from a base or partial abstraction of a proton from an acid that lowers the free energy of the transition state. A) True El) False 7. [on channels can open in response to which of the following A) Binding of a specific ligand B) Changes in membrane potential C) Changes in pH D) All of the above 8. Competitive inhibitors generally are most effective when they resemble the substrate, rather than the transition state. A) True B) False 9. What is the effect of cholesterol in a membrane? A) Reduces membrane fluidity by limiting acyl chain movement. El) Increases membrane fluidity by preventing acyl chain packing. C) Both ofthe above D) None of the above It). The role ofVitamin A is in A) blood clotting B) vision C) calcium deposition in bones D) all of the above E) none of the above 1. The carbohydrate portion of a glycoprotein is found: A) on the anterior side of the cell membrane D) all of the above E) on the interior side of the cell membrane E) none of the above C) spanning the cell membrane 12. A Schif‘l’ base is an imine that forms between a primary amine and which of the following? A) ketone B) aldehyde C) al] of the above D) none of the above Version 3 WHSIEUCIT 10244 FAX 512|1T18135 ElIEIEHEl-‘I IIII't' UT AUSTIN + ELEETHEINIE HESER .0033’010 13. An enzyme class that makes double bonds is A) isonicrase B) ligase C) hydrolase D) transferase E) none of the above 14. In a simple enzyme-catalyzed reaction, as substrate concentration increases the reaction velocity: A) increases logarithmically at higher substrate concentration B) increases at a lower rate at higher substrate concentrations C) continues to increase linearly at higher substrate concentrations D) none of the above E) all of the above 15. Movement of the oxyanion further into the active site, where it can be preferentially bound, stabiliZes the transition state of the chyrnotrypsin mechanism. A) True B) False 16. One's ABO blood type is determined by the presence of a terminal galactose or N—acetylated galactose in the oligosaccharide component of one‘s red blood cell glycoproteins. A) True 13) False 17. The sodiumnglueose transporter is an example of a(n) A) symport B) antiport C) uniport D) none of the above 18. Amino acids that participate in acid~base catalysis include all EXCEPT: A) arginine B) cysteine C) lysine D) aspartic acid E) tyrosine 19. Which of these characteristic(s) is/are found in naturally occurring fatty acids in mammals? A) most, but not all fatty acids contain an odd number of carbon atoms B) they are found free and un—associated with other molecules C) they are amphipathic D) if unsaturated, they occur in the trans configuration 20. Which of the following is are common intermediates of carbohydrate, lipid, and amino acid metabolism? A) pyruvate E) aoetyl Co-A C) glyceraldehydc-3-phosphate D) all of the above 21. In the induced fit model of substrate binding, the enzyme undergoes a conformational change upon binding such that it surrounds the substrate. A) True B) False 22. Which of the following is (are) found in a glycerophospholipid‘i' A) esterified fatty acid group D) all of the above 13) phosphate derivative as the head group E) none of the above C) glycerol backbone 23. NAD+ carries two electrons. A) True B) False 24. Together the effects of proximity and orientation can account for most of the increase in reaction rate seen with the addition of a catalyst. A) True B) False 25. Since thioesters have less resonance stability than oxygen esters, their hydrolysis is more exergonic than the hydrolysis of an oxygen ESTEI'. A) True 13) False Version 3 Page 2 WHEIEUCI? 10:44 Fhil 5124?1|3135 BIDEHEl-l DI'v' UT AUSTIN + ELEETHEINIE HEEEH IUUMUW 26. 27. 28. 29. 30. 31. 32. 33. Phosphofi'uctokinase is allosterically regulated by A) ADP. which is a positive effector increasing the activity. B) Phosphoenol pyruvate (PEP), which is a positive effector increasing the activity. C) the binding of ADP and PEP at the active site. D) A and B E) B and C F) All of the above. A newly discovered single-reactant, single product reaction in a metabolic pathway is found to have a standard fi'ee energy change of 2.6 kJ/mol. What is the free energy change at 37“ degrees C when the concentration of reactant is 4 mM and the concentration of product is l5 mM? A) +2.2 lemol B) —O.S kJ/mol C) +3.0 kJ/mol D) +6.0 kJ/mol KM is formally defined as the substrate concentration at lf2 anx. but what is another, less formal meaning giVen to KM? A) approximates the dissociation constant of [ES] and is used as a measure of the affinity of an enzyme for a substrate B) measure of the number of reactions by an active site per unit time C) measure of the rate of the reaction D) none of the abmre Which phospholipid would you choose to make a membrane that would be fluid at very cold temperatures? A B C its A) B B) C C) A D) none of the above Concerning the effect of mixed inhibitors on a reaction A) the Vmax increases D) A and C B) the Vmax decreases E) El and C C) the apparent Km may increase or decrease Which ofthe following essential amino acids are missing in corn? A) Leucine B) Phenylalanine C) Tryptophan D) Histicline E) All of the above What characteristic of enzymes makes them ideal catalysts for biological systems? A) Decreasing the activation energy of the reaction. E) Promoting the formation of the transition state. C) Increasing the local concentration of reactant molecules. D) all of the above E) none of the above Vitamin D A) requires UV light for synthesis D) all of the above B) may be obtained from the diet E) none of the above C) is a steroid derivative Version3 Page 3 10HSH200T10245 FMi 5124?18135 Matching regarding Michaclis~Menten kinetics: a. [S] {liken-competitive C. kflfll D. Km E. velocity F. initial velocity G. maximal velocity H. hyperbolic l. sigmoidal J. competitive 34. A co I - nund that affects the anu but not the KM is a A) C) o) E) F) o) H) 35. The symbol for tb u ichaelis constant is A) B) C) E) F) G) H) 36. The velocity at the start of the A) B) C) D) E) The equatio A) B) (:5; D) G) H) 37. E) F) G) H) 38. period, is called the A) B) C) D) F) G) H) 39. A) B) C) D) E) F) G) 40. When enzyme is saturated with subst A) B) C) D) E) F) 41. Jen PC a C) Use the figure belmv to answer the following questions: H) D) E) F) G) H) A)B B)C C)E D)A 43. A)C B)A C)E D)D E)EandD 44. A) D B)C C) B,C D) A,C EJA F) 45. A) [BLVD B) 1N0, l/[S] C) l/[S]. INe BIDEHEl-i IIII'u' UT AUSTIN inhibitor. 1) J) '1) J) tion. or VB, is called the I) J) = Vim/[Eh- describes the turnover number. 1) J) I) J) The plot of substrate concentration versus Vo results in a "l curve. l) l) I) .l) 1) J) . Which line(s) correctly identif‘ aeompetitive inhibitor? G) D F) none ofthe above Which line(s) or point(s) correctly identifies the Vmax‘? Which point(s) or line(s) correctly identifies the Km? A.B G) B The y axis and x axis, respectively, represent in this figure: D) Va. [3] E) none of the abova VersionB Page 4 + ELEETHEINIE HESEH Iflflfiffllfl The progress of a reactiug measured as the disappearance of substrate or the appearance of product over a specific time the reaction approaches E . is equal to KM, the reaction velocity is Iqual to half the maximum velocity. lflflElfiZICIICIT 1'3245 Fhii 51247'18135 ElIEIEHEl-l DII'i' UT AUSTIN + ELEETHEINIE HESEH Iflflfir’fllfi 46. (7—11)1s it necessary to know [E]r in order to determine Vmu? A) No B) Yes 47- 64 2 pts each 47. The standard free energy (136”) A) varies with acncentration D) all of the above B) is a constant E) none of the above C) is determined at 37° C 43. AG A) cannot be used to predict direction of a reaction D) all of the above 13) is a constant E) none of the above C) varies with temperature and concentration 49. The scissile bond is the bond being cleaved during a proteolytic reaction. A) True B) False (7—32) Aspartate transcarbalnylase (A'I'Case) catalyzes the formation of N-carbamoylasparatc from carhamoyl phosphate and aspartare as the first step of the multli-step synthesis of CTP. Kinetic analysis of ATCase yields the following data. READ ALL QUESTIONS and then answer the following queStions about kinetic behavior of ATCase. with ATP a ion 3 '5‘ {5 on my in ATP ‘.—'l as are a Carbamoyl phosphate + Aspanarc i, E with CTP NCarbamoylaspartste —D- —} —-3-- U UMP —"' —-F UTP —I' CTP IAalun‘nItL'lluiM') 50. Would you expect that CTP would be an allosteric inhibitor or activator of ATCase? A) no effect B) activator C) inhibitor 51. What is the role of ATP in the allosteric regulation of ATCasc? A) The KM decreases in the presence of ATP and increaSes the affinity of the substrate B) ATP has no effect on the reaction C) The KM increases in the presence of ATP and decreases affinity of the substrate 52. Based on the information in the graph, is ATCase an allosteric enzyme? A) No a) Yes READ ALL OF THE. NEXT 5 QUESTIONS IN ORDER AS INDICATED BEFORE. ANSWERING ANY. Based on 9-16. 53. READ THIRD: Suppose the synthesis of palmitoyI-CoA were coupled with ATP hydrolysis to AMP and PPi. The standard free energy for the hydrolysis of the B—phosphate linkage of ATP is 42.2 kl - mol-l. O 0 II II I'lac—(Ulith—LJFU + (MA .3. A'I'I" _-_—_I- llgt'I—ICI'IJJ1.—C.'—H—K:I.>A+ AM'II’ 1' l'l', Is This coupled reaction favorable“? A) cannot determine from data B) Yes C) No Version3 Page 5 WHEIHEUCIT 10245 FAX 51247'18135 ElIEIEHEl-l IIII'u' UT AUSTIN + ELEETREINIE HESER IUUTHUW 54. 55. SIS. 57. READ FIFTH: What is the overall AG‘“ for this reaction; 0 U II II [he—(CH9. ‘-ti-—tJ + one + m2 =Htt:—iet-rn. .—c—s—cm + as”: + 21:, A) -35.5 kamol )3) —34.2 lei/Incl C) 62.5 kJ/mol D) -33.5 kJImol READ FIRST: Palmitate is activated in the eel] by forming a thioester bond to coenzyme A. The 436‘“ for the synthesis of D H th—tCJ-lz‘lH—C—O' +£3.31. = 0 || palmitoyl-CoA from palmitate and coenIryme A is +315 k] - mol-l. |'|.y"-l""lfll'la)n—C— 5—0m + 112.0 Is this reaction be Favorable? A) No B) cannot determine from the data C) Yes READ FOURTH: Now atlppose the synthesis of palmitoyl-CoA were coupled with ATP hydrolysis to AMP and hydrolysis of' pyrophosphate. PM to 2E. The A0“ For hydrolysis of pyrophosphatase is 63.5 kJ/rnol. ‘i’ ii l‘l,t.i—ICl-I_.J. .—c—o + um. ---- A'I‘)’ =tIs.1~tc:l-In..—c—s—um + mm + 2 in Is this coupled reaction favorable? A) No B) Cannot be determined from the data. C) Yes READ SECOND: Suppose the synthesis of' palmitoylaCoA were coupled with ATP hydrolysis to ADP. The standard free energy for the hydrolysis of the y—phosphate linkage of ATP is -30.5 kl - moi-1. U U . . II. . _. || high—(Limp. —(.—U + (“A + ATP .— k‘l_.(.I—l(:l‘l_l)1..1—(:_5"'CUA + may 4- l": Is this coupled reaction favorable? A) cannot determine from the data [3) Yes C) No Read all questions in indicated order. Based on 660. 53. 59. 60. READ THIRD. You carry out mutagenesis of the putative active site and obtain the following Km data: I{-I1'I kfll'll His-Lys-Ser 5 520 His-Lys-Ala 302 6.6 His-Lys-Thr 8 467 His-Lys-Asn 20 l 50 Do these data support your theory that the His-Lys-Ser is the catalytic tried for this new class ofproteases'? A) No B) cannot determine from these data C) Yes READ FIRST. You have isolated a new class of proteases that are specific for cleaving after acidic residues. Initial structural studies show that the active site contains a catalytic triad of His—LysaSer. Given your knowledge of the ehymotrypsin protease catalytic tried and mechanism. do you think that this is a possible new catalytic triad? A) No B) Yes READ SECOND. For your new protease you inspect the structure and determine the location of the specificity pocket. What amino acid(s) do you expect to be in the pocket to provide substrate specificity? A) tyr or phe E) lys or arg C) glu or asp D) ser or flu Versioufil Page 6 torisraoor 10:43 Frill 5124?18135 ElIEIEHEl-l DI'v' UT AUSTIN + ELECTREINIE HESER IOCIBs-“CI‘ICI (based on 8-44) You have isolated a new type of choline transport protein implicated in movement of choline into liver cells. Using mouse models and a fluorescent labeled choline analog. you have measured the uptake of choline into liver cells. With the following results. 7 ___ _ __ .E u a-fl—r— —._. t? . ll . 4 ' g a CH e 2 I: '§ ._ HD—(CHflr-dil—CH; p __ _._ ._l_;n ”.20" CH, [Chollnel (an) Choline [’Hl Gllulmll unlrille by chllHMEle I-lmnalucmd sell- Read the questions in the indicated order and answer the following questions. 61. 62. 63. 64. READ THIRD. Choline concentrations in the plasma are 4-10 uM range. Does the transporter function fully at this concentration? A) No B) Cannot tell from data C) Yes READ FEURTH. This compound might be expected to transport of choline. .| Ill”, ch-Cl'Lz—NLCHJ—Cl'l, CH; CH“ 'lt-trumhylmnmomum I'l'PM A) inhibit B) not effect C) stimulate READ SECOND. What are the approximate Vmax and KM respectively for this transporter? A) 5. 50 B) cannot determine from data C) 50.5 D) 7. 35 E) 35, 7 READ FIRST. Can MichaeliSHMenten-liko behaviours be used to determine the affinity ofthe transporter for choline and the maximal rate of transport? A) No B) Yes 65-70 3 pts each 65. 66. 67. There are few examples of inhibitors that decrease Vrnnx but do not affect KM, these inhibitors A) are called non-competitive B) affect keg: C) affect the catalytic function. but not the binding of substrate D) all of the above E) none of the above The drug lenown as Botox is a preparation of botulinum toxin. How does this account for its use by plastic surgeons to alleviate facial wrinkles? A) SNAREs function by forming ot—helical bundles to fuse synaptic vesicles with the plasma membrane 3) botulinum toxin targets SNAREs for degradation by proteoiysis. C) SNAREs are necessary for transmission of signals from facial nerves to muscles via synaptic. D) all of the above E) none of the above (7-15) The enzyme hexokinase acts on 6 carbon sugars in carbohydrate metabolism. From the data in the table, answer the following question. Substrate Km anx fructose 7 x 10“ 1.8 glucose 1 x 10“ 1.0 The higher KM of fructose indicates it has a lower affinity than glucose, but the V...“ indicates that once bound, fructose is converted to product faster than glucose. A) True B) False Version 3 Page 7 WHEIEUCIT 10:43 Filii 512|1T18135 ElIEIEHEl-‘I IIII'u' UT AUSTIN + ELEETHEINIE HESER IUUEIUW 68. Place the following steps of the ehymotrypsin mechanism in the correct order: 1. Water enters the active site 2. Formation of tetrahedral intermediate, l-lis donates proton to Set 3. Removal of Set hydroXyl proton by His 4. Formation of tetrahedral intermediate, His donates proton to substrate 5. Departure of original substrate C-terrninal portion 6. Departure of original substrate N—terminal portion 7. Binding of substrate A) 7, 5, 3, 1,4,2,6 B) 7, 3,4, 5, 1,2,6 C) 7,4,3,2, 1,5,6 D) 7, 1,2,4, 3, 5,6 E) none ofthe above 69. (9-3) The AG°' for the formation ofUDP—glucose from glucose-l -phosphate and UTP is about zero. Yet the production of UDP—glucose is highly favorable. What is the driving force for this reaction? Glucose-l—phosphtlte + L'FI'P‘ = EDP—glucose + PP, A) the enzyme's active site D) UDP is a higher energy compound than UTP B) irreversible hydrolysis of PH E) all of the above C) glucose undergoes a conformational change F) none of the above 70. Place the steps of the Na,K-ATPasc transport cycle in the correct order: l. TWo extracellular K-l- ions bind 2. ATP binds 3. Protein conformation occurs, Na+ ions dissociate 4. Three intracellular Na+ ions bind 5. ATP phosphorylates protein 6. Protein conformation occurs, K+ dissociate 7. Protein dephosphorylates A) 4,16,11,75 B) l.2.6,4,3,7,5 C) l,2.5,3.4.7,6 D) 2,4,5,3,l,7,6 E) 2,1,5,4,7,6,3 F) 4,2.5,3.],7.6 VersionEl Page 3 10x133200? 10243 FAX 5124?1B135 BIDEHEI'u'I DI'v' UT AUSTIN + ELECTRDNIE HESER INCH-“010 Answer Key Fwsmw+uHH Lu) J: mnnn>mmm>n>om>mw>mbwhhmfiqfiuDomw>U>>m>u>un>>>>mmn>mnmumwnumn 1$=mfimom Version] Pagc 9 ...
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