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Unformatted text preview: 10/16/2006 12:41 FAX 512 471 6135 BIOCHEM DIV —> ELECTR RESERVE .001 CH 369 October 12. 2006 Exam Two mum“ at... ................... ‘ Questions [-5] are each worth 1 pt. Osteoelnsts in bone tissue are rich in carbonic nnhydrose [I and enzyme function: is necessary for bone development. The onteoclairt muat acidity the extracellular environment for bone development. Several ion exchangers are involved in this process. Based on 8-43e. Answer the following questions N11. or if m . Honour - ' No it Halli 'mfilqt— ‘ "\ufillfl’tiglhr a. 'n fir+ l Belle-to screen-5:1 1 camper—"imam e H 5.5 EIKEF'IBI'IE’BI' 1. ' h is the eon-eel reaction catalyzed by carbonic onhydrnse II in the osteoclnsts: O: + 1-an ...:. H“ + HCO:' 13) H" + l-ICOJ' "-3- tlzCOs C) H1003 -—3=' C0: + H20 D) none of the above are correct 2. a. the Na-I-IK-I- transporter, which of the following are true a he Na+ will move out1 the K+ will move in B) The Ne—l- will move in, the K-l- will move out _ .- 3. For the Cl-Il-ICOJ- transporter, which of‘ the followi 1 . * true A) The Cl- will move out. the HC03' will move inihc (01- will move in, the HCOa' will more out _,,_—- mom...— 4. For the Na+iH+ transporter. which of thc followi : - true: A) The Nor will move out, the H+ will move in “he No+ will move in, the l'l-l- will move out 5. These ion exchangers are examples of A) syrnports B) diFfiJsion C) uniports.nlipor1_|l E} none ofthe above TmelFalse. 1 pt each 6. N-linked oligosaceharides, such as N—acctyl galactosaminc. are alluchcd lo the side chain @31‘ W True ahte 6? 711111113? ucids are thougm to be bad because the they Increase the level oi ”had" cholesterol (LDLS) leading to heart disease. rue F also 5% 1+ 0+ Chara l- L) B especificity pocket for trypsin contains a negatively charged amino acid. MWL L'lj 5 l 6 C0 A me 13 False Q 9. or] coagulation is an example of a protease cascade l’er enzyme activation. rue False *1.er 11] Since the components of biological membranes can pass fluidly from one side to the other, [he outer and inner surfaces of cells have similar compositions. True alse ®f Version I 10/16/2006 12:42 FAX 512 471 6135 BIOCHEM DIV a ELECTR RESERVE .002 ii. The action potential is able to travel in both directions depending upon where along the axon it starts. Ag Trim Wigs: L“ Duh-3 \ gauche“... [I St: l2. 'ans fatty acids are made by hydrogenation of unsaturated Fatty acids in oils to improve their slielflife. true 13) False l3. Allosteric regulators only inhibit enzyme reactions. A. True False l4. ' neurotransmitter neelylcholine is released into the synaptic cleft as a response to an increase in the intracellu‘oncentration. THE B False 15. An enymatie catalyst differs from a chemical catalyst in that the enzymatic catalyst is consumed in the reaction. :5: £"“%fiMb ire-Man‘s Lo Dr'efltmk Wife»- [6. The catalytic triad of ehymotrypsin contains Asp. His and "gilt. ‘33-!" ‘ True alse l7. drogen bonding of the oxyanion with protein backbone groups stabilizes the transition state during the enzymatic reaction of ehymotrypsin‘ the 13) False rue l8. " e activation energy is the Free energy of the transition state minus the Free energies of IJ'Ie reactants. False l9, ' ee thioesters have less resonance stability than oxygen esters. their hydrolysis is more exergonie than hydrolysis of'oitygen esters. I'llC B) False "JD 20 most potent enzyme inhibitors ofien resemble the transition state of a substrate. False 21. Proximity and orientation can account for all of thc increase in the reaction rate seen with the addition of an enzyme catalyst. oft”; Meal/rem "I“: ”fit-i Wooden" 22. One‘s ABO blood type is determined by the presence ot‘a terminal galactose or Nuacetylated galactose in the oligosacchuride component of ones red d cell glycoproteins. ‘ true El) False Multiple Choice, 1 pt each. Choose the BEST answer. 23. ipetitive inihibitors have the following effects orl KM and anx; hey alter the value of KM but not Vim \u-i" D) none of the above B) they alter the value of Vim but not KM at E) all of the above C) they alter the value of both KM and Vm“ K. 24. Which vitamin can act both as a 1' receptor and a hormone? A) Vitamin K B) Vitamin C itamin A D) all of the above E) none ofthe above 25‘ In contrast to inorganic eataiy zynies have an intricately shaped surface called the A) Substrate B) Catactor ctive site D} Apoenzynie E) Holoenzyrne 26. ADP regulation ofphosphotructoltinase activity is a type ol": ; suicide substrate inhibition D) competitive inhibition @ allosterie regulation E) none oi‘ the above transition state inhibition 1") all ot'thc above VersiOn T'i Page 2. 10/16/2006 12:42 FAX 512 471 6135 BIOCHEM DIV a ELECTR RESERVE I003 27. Enzyme control is accomplished in which of the following ways in a cell? A) Genetic control ‘I_ Compartmentalization B) Covalent modification All of the above are correct. C) Aiiosteric regulation 28. Which ofthe Following amino acids is e ot'participating in covalent catalysis? WA) Tyr L"5) Lys C) Mp1 D) asp , B F) A. C: G) A. D H) none of the above i) all of the above 29. Depolarization of‘a membrane: A) is called action potential "f A and 13 B) results in a negative membrane potential 7': A and C 1.4 C) can stimulate the Opening cation channels pr' All of the above 30. The main type(s) of enzymatic catalysis islare: A) acid/base El) covalenteatalysis C) metal ion catalysis®lofthe above E) none of the above 31. Which of the following maerotnoleeules provide the most metabolic energy? A) oucleichgids, proteins, triacylglycerols D) nuelefi'aclds. polysaccharides. triacylglycerols fl)! proteins. polysaccharides. triacyigiycerois v” E) none or the above nucleicjllids. proteins. polysaccharides 32. The initial velocity (vii) oi" an enzyme-catalyzed reaction A) decreases as me substrate cancentration increases D) is independent of the pH of the solution is lowest when the enzyme is saturated with substrate E) all of the above is dependent upon the substrate concentration 33. integral membrane proteins that act to lose and link membranes are called' A) myelin sheaths B) porins C) sphingolipids D) aiioi’the above®one ofthe above ‘5an 34. The masimum velocity: A) has the symbol Vina): V! D A and B B) can be expressed as equal to ltz[E]Tat high [S] 1/" A. E. and C C) occurs when all enzyme is in the saturated form V" 35. An allosterie enzyme A) has only one active site 7"- D) catalyzes more than one reaction within a metabolic pathway X 13 is always regulated by covalent modification '7'- E) all ol" the above has more than one polypeptide chainlr" 36. Which of the following residues would you expect in the membrane spanning portion " integral membrane protein? A) LHand Val 13) Leu and ill; C) CM and A§fi D) Alband Val E) A and El and D , P. v 37. .3 ouble bonds in naturally occurring Fatty acids are usually .......__..-.._.,.. isomers. IVs 13) Trans (2‘) Equal cis and traits D) none of the above 38. What is the effect ofeholestcrol in a membrane? A) increases membrane fluidity by preventing acyl chain packing.“ @3001 of the above El) Reduces membrane fluidity by limiting acyl chain movements.» D) Neither ofthe above 3'9. When considering the effect of‘ the active site of an enzym ' l ofthe following play an important role in enzyme catalysis: A) proximity-’13) orientations-rift) exclusion ot'solven @‘ l ofthe above E) none ofthe above 40_ The enzyme turnover oun'tb ' - cribed bythe rate constant___w_flw. A) Va 0) Km C) K. 8E) none of the above 4-1. The active site of an enzyme A) is termed only after phosphorylation events “r" B) is directly involved in binding of ailosteric inhibitors *1 resides in a few adjacent amino acid residues in the primary sequence ot‘the polypeptide chain)“: binds competitive inhibitors V!“ 1:) none of the above 42, The steady state For enzyme kinetics assumes X _-. The amount of product will decrease during the reaction. E, The rate of Formation of [EB] is eauai to the rate of consumption of [5] over the course of the reaction?! The rate of fon‘oation of [ES] exceeds the rate of consumption of [3] over the course ot‘ the reactions: D) [S] will increase during the reaction. )6. Version I Page} 10/16/2006 12:42 FAX 512 471 6135 BIOCHEM DIV —> ELECTR RESERVE I004 43. The lock and key model of enzyme activity proposes that A) Each enzyme can react with only a single specific substrate" B Each enzyme has a cofactor that promotes the catalytic activity. ’2 CEbEach enzyme binds its substrate(s) because the active site and substrate(s) have complementary structures V“! 0th A and B are correct. E) Both 3 and C are correct, F) nonc ot'thc above 44. Which ol'thc following is a propertyy/ofcnzymcs? A) Capable of being regulated B) Reaction rates ans/high in comparison to uncatalyzed reactions. P” C) Highly specific 45‘ Most tissues pref 1 5c as the primary fuel. A) amino acids ‘Iucose C) triacylglycerols D) none oFthe above E) all ol’the above 46. In addition to enzymes. what othgypes of proteins demonstrate saturatio- - '.-"{ A) Ligand-binding proteins $0 of the above B) Certain types of membrane transport proteins 1"" r ' none of the above C) Oxygen binding proteins we“ I. ide products ofthe reactions are rare. H”- a. II ot‘thc above are correct. 47. Channels that allow ions ove down a concentration gradient are called: A) active transporters assivc transporters C) antiport transporters D) symport transporters E) none of the above 48. Mixed inhibitors have the li‘ollowing et‘liccts on KM and Vum: A) They alter the value of KM but not Vm " D) none or the above They alter the value of VW but not KM "- E) all of the above “hey alter the value ol" KM and Vum pr" :19. Feedback inhibition is a feature of‘wbat type oi’e tic control?I A) Genetic control B) Covalent modification wile-stem: regulation D) Compartmentaliaation E) Both l3 and C,‘ are correct, 50. Which animal organ receives the f nutrients and actively stores, catabolizes, or releases them back into the bloodstream? A) stomach 13) large intestine ver D) none ot'the above E) all of the above 51. h ofthe following will increase membrane fluidity? cducing fatty acid scyl chain lcngth if" D) A and 6 Increasing fatty acid acyl chain saturation V E) All of the Above C) Reducing membrane temperature '54! Questions 52-62 are each worth 2 pts each. Multiple choice. Pick the BEST single answer for the multiple choice questions. 52. l-i‘ the enzyme concentration For a biochemical reaction is increased IOU-fold, the equilibrium constant for the reaction will A) increase IOU-fold 3': D) change inversely with the enzyme concentration 1"- remain the same E) none at" the above increase in proportion to the enzyme concentration X 53. Human cell Surface proteins are labeled with a red fluorescent marker and mouse cells are labeled with green fluorescent maker. The cells are induced to fuse forming a hybrid ccll. What is the expected result? . . L - 1. @mmedimely following l-‘usion= the cell is an even mixture cited and green)“z '5"- P'it'w“ L“ E" d‘i’S 9‘ him. After incubation for 1 hr at 37 “C, the cell is an even mixture of red and green?" ) Alter incubation for 1 hr at i5 ”C, the cell is an even mixture ofred and green. )1. tht-vvJa'rca we. “,3? .9“); d erl’lUUC‘Sh ml. l5” LO D) None of the above E) All ot'the above all M» launch“. mew-e mar-Ni“ sat.- crawl Vcrsion 'l Page 4 10/16/2006 12:43 FAX 512 471 6135 BIOCHEM DIV —i ELECTR RESERVE .005 Use the diagram to answer the following questions (54-57): fl 5 BA .5 “E 0.2 -a e u { _;,_ o.I *4 -2 t E 4 mM Substrate 54. Curve C depicts the effect of a different inhibitor of the system described by curve A. This second inhibitor A‘ is a competitive inhibitor D) decreases the Ku 's a non-competitive inhibitor E) C and D increases the Vm F) none of the above 55. The value oi’Vm For the enzyme depicted by curve A ' y 3 l O A) 0.1 micrOmoli’min/mg El) l Inicromol/min/[email protected]/min/mg D) [1ij E) 2 mM 0‘ 56. value ol‘KM For the enzyme depicted by curve A is l S @5 mM B) 1 mM C) 2 mM D) l micromol/min/mg E) l0 micreImoI/min/n-Ig I2 =- 0 4' 57. ve l3 depicts the etTeet of an inhibitor on the system deacribed by curve A. This inhibitor “is a competitive inhibitor D) decreases the KM is a non-competitive inhibitor E) C and D C) increases the me F) none of‘ the above The plot represents the relationship between substrate concentration and velocity for a single enzyme in the ahsence(e|1rve x) and presence (eurw: y).ol‘a compound that binds nllosterlenlly to the enzyme. Use the figure below to answer Questions 58-59. NVMacfifl. Chung Km 9303.91 QLMVX [Substrate] 58. In the presence of the allosterie compound A) KM and Vs.“ both increase ? KM decreases and V...“ increases B) KM and Van“ both decrease M decreases and V...“ stays the same C) KM increases and deecreases 59. The allosteric compound is A) a competitive inhibitor Fl) a non-competitive inhibitor C) an irreversible inhibitor. activator E) none ofthe above 60. Pure chymotrypsin is stored in a dilute solution of hydrochloric acid, why? Based On 6-32. A The acidic solution keeps bacteria and fungi from growing in the solution lhe acidic solution keeps an amino acid In the. active site protonated inhibiting activity. The acidic solution keeps the carboxy terminus protonated to keep the protein folded correctly Lf‘iafi EC 3(15 D) none ofthe above re,” H {Loire-1'37 1.3.41} -cs— F" trawl? 51. glucose-(impliosphate~t-l-120 a»: glucose -I- Pi AG”'= -13.s kJ/rnol 1' i3" 5 555‘) R pct P 4- ”Kw 4'22 (EM {3 "i“ ADP 4- Pi {n} A'I‘P+ H20 AG“'- +305 kJ/rnol — 2.0. E; Emmi—A. — — —— —--—-— .1 13- TATE P . . , . i”iim".l excess 4- me “=5 554*" ’ What Is the AG" 1’ ‘ rrnatIon oFglucOse-tS-phosphute In the first step at glycolysis‘? Q A) +1637 kJ/mo ) - .7 Miami C) +443 kJ/Inol D) «44.3 kamol E) none are correct Version it Page 5 10/16/2006 12:43 FAX 512 471 6135 BIOCHEM DIV -I ELECTR RESERVE I006 62. The active sites of enzymes eliminate the energy barrier of'thc solvent molecules through a precess known as electrostatic catalysis This means that the active sites exclude water molecules. However. some enzyme mechanisms including chymotrypsin use water during the catalysis. How is this possible considering the mechanism ol‘ehymotrypsin'? s The Water molecules "hide" in the active site by bonding to odIer hydrophilic residues): * he water is only allowed to enter after another molecule exits. The water is at such a high concentration it forces its way into the active site. 3‘ D) All ofthe above E) None ot'the above Questions 63-71 are each worth 3 pts. Use the following infurmation to answer questions 63-67. Read all questions before answering any. Based on 6-40. An enzyme was recently purified and characterized from rabbit brain. It is an aspartyl aminopeptidase. which hydrolyzes peptide bonds to the carboxyl side of til-terminal nspartate residues. As II medical scientist you are interested in this enzyme III; II potential target for drug therapy. so you want tn know moi-I.- about the active site and substrates of tlltI enzyme. You synthesize II variety of peptides and determine their let-M . The enzyme cleaves the substrate between AAl-AAZ. It is believed that both the AAZ and AM! residues have adjacent specificity pockets. Peptide (Ml-m-AAs-AM} lemon") Ash- . -Ala-Leu C1533.) Jr— As AlarLeu F3543. rt" Asp- "-AIa—Lcu Asp Phe-Leu I” Asp-Aia-Lys-Leu . I Asp-Ala—Asp-Lcu 2.3 MPH-J 63. Which best describes the characteristics oFthc spccitlpékct f . Mm: acids The pocket Is better able to accomodate prl 61y chorg .. #Thc pocket Is better able to accomodate larg-gavnd small non-polar amino acids.\/ C The pocket is better able to uecomodute only small polar amino acids. D) The pocket is better able to accomodate all amino acids. E) new of the above. fimUO-fll} 64. Because you isolated this enzyme from rabbit brain. you think that it might have a neurological role in the Formation or degradation ofncuropeptides. You note that aspartame, an artificial swcctncr that is a dipcutidc (Asp-FlIe-O-Me). might be a substrate for this enzyme. Aspartame has has! a significant number of side effects reported including neurological ones. Aspartame. as a substrate of your aminnpcritidasC. could interfere with neurological function as a competitive inhibitor of the enzyme. thus reducing the : I'lity ut'tlle enzyme to either activate via proteolysis or eliminate by degradation neuropeptidos resulting in neurological symptoms I'L'IC False This is a. plausible. ionic-L baits-ii cw Clfipcqusyw acne. “ (assessors H 65. You want to measure the activity ofyour enzyme with aspartame to test your hypothesis and find the following results; Juli-'7 Substrate its“ K... W. dipeptlde 1 (good substrate) 43 0.1 mM l _ ll it? it: anr 4‘3 (.3 . .r-_' . ii" . aspartamc 4 100 mM 12"“ 4,5,5, $258“ $4,: bu PM “LO Ugh “CEL- L‘E LESW D! I 0+ You conclude from these results that aspartarne would be an effective inhibitor under physiological conditions. W3 A Truc y: Qimllw. Wall's -alse 0" P chili-3h El Ou-zabfilcl. “Hi Oi» You decide to chnL and overexpress your asparlyl aminopeptidase' In E. Coli. The enzyme irrIm E cnli has similar kinetic characteristics as the enzyme h-‘om \l rabbit brain. The exact mechanism" Is unknown. but it is speculated that two hisitine residues are precent' In the IIetive site. You mutagenize these two histidinr: residues and measure the catalytic aLtivityI ado Enzyme KM its... ell-”ii Km. 930 Wild Type (His292.I-ii5386) 4 532 l 3-5 X i\.I\J~h\ Mutant 1 (Lys 292. His 386) 326 4.5 gig. D Mutant 2 (Hit-.292, Lys 336) 6 408 5' '3 Mutant 3 (His 292. Arg 360) 500 0.02 E ifs Mutant 4 (Arg 292. His 336) 3 396 13;, 2. 66. Which mutant has a ca ' cfi'icicncy closest to the wild typc'l A) l B) 2 C) 3 E) none of the above _ Version | Pagcfi 10/16/2006 12:43 FAX 512 471 6135 BIOCHEM DIV + ELECTR RESERVE I007 67. Which ot'the mutants isatno - 'eient enzyme than the wild type? A) l B) 2 C) 3 D) 4 gene ofthe above The retina of the eye has special ECiiS, perieytes, that are deranged in the early stage nl'dinhetic retinopnthy that results in blindness, As a medical scientist you are interested in why these cells are damaged and note that perieytes have similarity to cells that possess a + -t ns orter scirr . You wish to determine if such a 5G]..T exists ill perleytes and il'exeess glucose transport into the cells may be the cause of the damage leading to blindness. Answer questions till-7|. Read all questiOns before answeringt Based on 3-421),; 63. You aI‘l‘leastll't.‘ the uptake of glucose into endothelial cell and pericytcs with increasing concentration ost-I- and get the following data: —w -—.m__‘ littdelltulml en'ltn E s -‘ fl 4—. _ i ' i-Mrlnyinn ii on g- 0.13 ' a D91 D 50 me 150 i-‘lllJ Gotten-union" ul Nn' mm [min] A rinse-dependent msnenuo lot the sodium-deported!“ uptake at clean-so L‘rv culleytus ima unauumtml cullll Which ofthe following statements concerning the date are correct: A) Endothelial cell uptake of glucose is inhibited by Na—l— of F) A and D B) Endothclial eell uptake of glucose is stimuluted by Na+"f G) B and E C) Endothelial cell uptake ot‘glueose is unaffected by Na-l- v" H) C.‘ and F D) Perieyte eell uptake of glucose is stimulated by Na+ v E and E E) Perieyte cell Uptake of glucose is inhibited by Nat y! Obi: and D 6*). Additional measurements of glucose uptake in perieytes are made in the absence and presence ofNa+ ions and the following kinetic dutn are obtained; Refer to the front cover of the exam if this Figure is too difficult for you to rend. -_ 0.5T: (If, i n no I/ l _ V ‘ JaLtfilhu UK. s * l s s - '33) MW e in: If KM 3" 0.25 of U "W 49'03’ PH smor— Me“ i H!” For" 555:." l' 1's a bush lira... ‘ rial roman ‘DLM‘E‘ all]. ...
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