Comprehensive - GKB-2009ExamQuestions Questions from 2009...

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Unformatted text preview: GKB-2009ExamQuestions Questions from 2009 exams 1) Which of the following best describes the entry of mannose into glycolysis? a. phosphorylated at C-1; UMP moiety transferred from UDP-glc; epimerized at C- 4; released from UMP moiety on next transfer as GlP b. phosphorylated at C—6; epimerized at C-2 to produce G6P c. phosphorylated at C—6; isomerized to produce F6P d. phosphorylated at C-1; UMP moiety transferred from UDP—glc; epimerized at C- 2; released from UMP moiety on next transfer as GlP e. hydrolysed into two glucoses, they enter normally 2) Which of these reactions never occurs in a human being? a. m—ketoglutarate + NAD" + CoASH asuccinyl-CoA + NADH + H+ + C02 b. glycogenm + phosphate “glucose-l-P + glycogenm-” c. maltose —>2 glucose d. succinate + FAD Hfumarate + FADHz e. pyruvate + NADH + H+-> C02 + ethanol + NAD+ 3) Conversion of galactose to glucose is accomplished by a. mutase b. kinase c. hydrolase cl. epimerase e. isomerase 4) Which enzyme catalyses a reaction with an enediol intermediate? a. Phosphoglucomutase b. Phosphoglucose isomerase c. Phosphofructokinase d. Aldolase e. None of the above 5) If glucose labelled at the 01 position with 1"'C passes through glycolysis, on which carbon of pyruvate will the radiolabel be found? a.1 b.2 GKB-2009ExamQuestions c. 3 d. It will be found on multiple carbons. e. It's impossible to predict. 6) Which of the following compounds contains a "high-energy" bond and is used to produce ATP by substrate-level phosphorylation in glycolysis? 3- cog I 1 C— 0P03" II 7) In skeletal muscle cells, the NADH that is produced by glycolysis under anaerobic conditions (vigorous exercise) is regenerated to NAD+ by the conversion of: a. pyruvate —>Iactate b. lactate qpyruvate c. acetaldehyde «rethanol d. glyceraldehyde-3-phosphate —+1,3-bisphosphoglycerate e. phosphoenolpyruvate *pyruvate GKB-2009ExamQuestions 8) During glycolysis, the steps between glucose and formation of the triose phosphates a. produce two ADP and two NAD+ molecules b. consume two ATP molecules c. produce two ATP and two NADH molecules d. consume two NADH molecules e. consume two ATP and two NADH molecules 9) The reaction below is catalyzed by yeast alcohol dehydrogenase. Which of the following corresponds to X and Y? O OH CH3<“:H + x 01113331412 + Y a. X: NAD+H+ Y= NADH" b. x = NADH + H+ Y = NAD+ c. x = NADPH + H+ Y = NADP” cl. x = NADH+ Y = NAD + H+ e. x = NAD+ v = NADH + H+ 10) In which of the following metabolic conversions is ATP "consumed" during glycolysis? a. 1,3-Bisphosphoglycerate —v3-phosphog|ycerate b. Glucose —»glucose—6-phosphate c. 2-Phosphoglycerate —>3-phosphoglycerate ci. GIucose-6-phosphate efructose-S—phosphate e. Fructose-1,6—bisphosphate edihydroxyacetone phosphate + glyceraldehyde-3- phosphate 11) Experimental evidence indicates that glyceraldehyde-3-phosphate dehydrogenase contains a critical residue in its active site, as shown by its inactivation by iodoacetamide. a. lysine b. aspartate c. cysteine d. alanine GKB-2009ExamQuestions e. methionine 12) Phosphofructokinase is allosterically inhibited by high concentrations of a. glucose b. ATP c. pyruvate d. fructose-6-phosphate e. None of the above 13) The enzymes that catalyze glycolysis are located in the a. cytosol b. mitochondrial matrix c. inner mitochondrial membrane d. endoplasmic reticulum e. nucleus 14) Which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose? a. phosphoglucose isomerase b. hexokinase c. phosphoglucose mutase cl. aldolase e. glucose-6-phosphatase 15) Which of the following is TRUE about competitive inhibitors? a. A. Competitive inhibitors lower the Km and the Vmax of the enzyme. b. 8. Competitive inhibitors structurally resemble the substrate and so they bind to the active site and become covalently attached to the enzyme. c. C. Transition state analogs often make better competitive inhibitors than do substrate analogs. cl. A and C are both true. e. A, B and C are all true. GKB-2009ExamQuestions 16) Which of the following methods of altering enzyme activity depends on the activity of protein kinases and protein phosphatases? a. Allostery. b. Product inhibition. c. Feedback inhibition. e. Covalent modification. 17) For a reaction A + B —+C, if the concentration of B is much larger than [A] so that [B] remains constant during the reaction while [A] is varied, the kinetics will be: a. zero-order b. enzymatic c. sigmoidal d. pseudo-first-order e. unimolecular 18) Irreversible enzyme inhibitors are also called: a. product inhibitors. b. covalent substrates. c. allosteric effectors. d. Ping Pong inhibitors. e. inactivators. 19) A Lineweaver-Burk plot is also called: a. a double-displacement plot b. a Michaelis-Menten plot c. a double reciprocal plot d. a sigmoidal plot e. a linear plot 20) A compound that reduces the concentration of enzyme available for substrate binding is called: a. a transition-state analog b. an allosteric effector GKB-2009ExamQuestions c. a non—competitive inhibitor d. an enzyme inactivator e. a competitive inhibitor 21) Protein kinases are involved in a. the digestion of drugs to potentially toxic byproducts b. the degradation of enzymes to the component amino acids c. the phosphorylation of a wide variety of proteins d. the metabolism of drugs to water-soluble, excretable compounds e. all of the above 22) Which one of the following mechanisms is NOT known to play a role in the reversible alteration of enzyme activity? a. Alteration of the synthesis or degradation rate of an enzyme. b. Activation by cleavage of an inactive zymogen. c. Allosteric response to a regulatory molecule. cl. Covalent modification of the enzyme. e Interactions between catalytic and regulatory subunits. 23) Which of the following statements about phosphorylation of enzymes is FALSE? a. Phosphorylation is a reversible covalent modification. b. The phosphorylation of enzymes is one mechanism via which hormones elicit an intracellular response. c. The phosphorylation of an enzyme results in a change in its conformation, thereby increasing its activity. d. The phosphorylation of enzymes is catalyzed by other enzymes called kinases. 24) Which of the following statements is INCORRECT with respect to covalent modification of an enzyme via phosphorylation? a. Ser, Thr or Tyr residues can be phosphorylated. b. Phosphorylation may either decrease or increase enzyme activity. c. Phosphorylation results in a change in the tertiary structure of the enzyme. 6 GKB-2009ExamQuestions d. Covalent modification via phosphorylation is irreversible. e. Phosphorylation modifies the size, shape and charge of the phosphorylated amino acid. 25) Which of the following is always involved in biological oxidation-reduction reactions? a. Inner mitochondrial membrane. b. Transfer of electron(s). c. Oxygen. d. Formation of water. 26) Which of the following phosphorylated compounds would be considered a "low-energy" intermediate in metabolism, relative to the others? a. Phosphoenolpyruvate b. ATP c. 1,3-Bisphosphoglycerate d. Glucose—6-phosphate e. Phosphocreatine 27) Which one of the following compounds is/are NOT used to synthesize ATP via a substrate-level phosphorylation reaction? 1) 1,3-bisphosphoglycerate 2) glucose-6-phosphate 3) phosphoenolpyruvate 4) 3-phosphoglycerate 5) phosphocreatine a. 2, 4, and S b. 1, 3, and 5 c. 2 and 4 cl. 5 28) Which of the following correctly describes a catabolic pathway? a. Catabolic pathways may require an input of energy. 7 GKB-2009ExamQuestions b. Catabolic pathways may reduce NAD‘“. c. Catabolic pathways synthesize larger molecules from smaller precursors. d. Both A and B are correct. e. Both B and C are correct. 29) Which of the following terms accurately describes an enzyme-catalyzed pathway that can both reduce electron carriers and extract usable chemical energy from fuel molecules? a. Metabolic b. Catabolic c. Anabolic d. Amphibolic e. None of the above 30) Why is acetyl-CoA considered a high energy molecule? a. Large amounts of ATP are released upon oxidation. b. It contains a thioester bond. c. It contains an ester bond. d. Large amounts of ATP are released upon deacetyiation. 31) In the graph shown which of the following statements is TRUE concerning the ”plateau" region of the curve? Reaction velocity. v Substrate concenlratlon. [S] GKB-2009ExamQuestions a. All the available substrate has been converted to product. b. The enzymes active site is saturated. c. The enzyme is in the tense state. d. A and C. e. A and B. 32) Which two curves in the graph best illustrate the change in the activity of an enzyme that occurs upon adding a competitive inhibitor? Reaction Velocity v Substrate Concentration [S] a. 3 without inhibitor to 2 with inhibitor b. 2 without inhibitor to 1 with inhibitor c. 4 without inhibitor to 3 with inhibitor d. 3 without inhibitor to 4 with inhibitor e. 1 without inhibitor to 2 with inhibitor 33) While is always involved in reactions that require the transfer of 2 electrons, can participate in reactions that transfer either 1 or 2 electrons. 9 GKB-2009ExamQuestions a. FAD; NAD” b. flavin; niacin c. 02; NAD+ d. NAD”; FAD e. MAN; 02 34) Where does ATP hydrolysis rank among the standard free energies of phosphoryl group transfer of all biological molecules? a. ATP hydrolysis has nearly the largest negative free energy change. b. ATP hydrolysis has an intermediate free energy change. c. ATP hydrolysis has nearly the smallest negative free energy change. d. ATP hydrolysis has the largest negative free energy change. 35) Which amino acid is most likely to act as a covalent catalyst in an enzyme active site? a) Met b) Ala c) Ile d) Ser 36). Which statement best describes the model of "induced fit"? a) Enzyme-substrate binding induces a conformational change in the enzyme, such that the binding site better conforms to the shape of the substrate. b) Enzyme-substrate binding induces an increase in the reaction entropy. c) Enzyme-substrate binding induces formation of the transition state, which reduces the free energy of the reaction. d) Enzyme-substrate binding induces enzyme specificity. 37). A well-designed enzyme active site provides which of the following features? a) A. Complementarity of shape and chemical nature to the substrate(s). b) B. Proximity and correct orientation of substrates and catalytic groups. c) C. Complementarity of shape and chemical nature to the transition state. d) Both A and B but NOT C are correct. 10 GKB-2009ExamQuestions e) A, B and C are all correct. 38). Consider Figures 1 and 2. Choose the statement that is TRUE. Free Reaciants Free -..__ __ ._.. energy wig?" (G) Products AGraaciion ______ AGIeachon Products Fieaclants Reaction coordinate Reaction coordinate a) Figure 1 shows a greater activation energy barrier. b) Both reactions are spontaneous reactions but Figure 1 has a negative delta Greaction. c) Figure 2 represents a fast reaction while Figure 1 represents a slow reaction. d) Figure 1 represents a spontaneous reaction while Figure 2 does not. 39). Which of the following statements about catalytic mechanisms of enzymes is TRUE? a) Enzyme catalytic mechanisms always require the formation of covalent intermediates. b) Enzyme catalytic mechanisms always require specific positioning of substrates and catalytic. c) Enzyme catalytic mechanisms always require the use of acidic and basic R groups. :3) Enzyme catalytic mechanisms always require prosthetic groups and R groups. 40). Which of these amino acid groups would not make a good nucleophilic catalyst? 1 1 GKB-2009ExamQuestions a) imidazole b) methyl c) hydroxyl d) sulfhydryl e) amino 41). Which of the following amino acid residues would not provide a side chain for acid-base catalysis? ) histidine ® leucine c) serine d) lysine e) aspartic acid 42). is a serine protease that has a specificity pocket that binds small hydrophobic side chains. a) lysozyme b) chymotrypsin c) trypsinogen d) trypsin e) elastase 43). Curved arrows are conventionally used to illustrate the movement of: a) electron pairs. b) single electrons. c) protons. d) anions. e) all of the above. 44). The catalytic mechanism of bovine pancreatic RNase A relies upon acid/base catalysis involving the amino acid a) histidine b) aspartic acid 12 GKB-2009ExamQuestions c) arginine d) imidazole e) lysine /5/). The 'catalytic triad' in chymotrypsin consists of: a) three amino acids: SER, HIS, and ASP b) three amino acids: CYS, HIS, and ASP c) substrate, transition state, and product d) three amino acids: SER, HIS, and GLU e) enzyme, substrate, and metal-ion cofactor )5). In the lysozome reaction the subsite D NAM is in the conformation. ' a) staggered b) boat c) chair d) half-chair e) furanose MThe oxyanion hole in serine proteinases illustrates which of the following mechanisms of enzyme action? a) Preferential transition state binding. b) Induced fit in substrate binding. c) Reduction of the activation energy barrier. d) The role of serine side chains in proteolysis. 48). D-glucose has 4 asymmetric carbon atoms. How many epimers does it have in the D-configuration? a)0 b)3 c)4 d)8 49). Which of the structures is a glucopyranose? 13 GKB—2009ExamQuestions C D a) A b) B c) C d) D e) None of the above. 50). Which statement best explains why nonpolar substances have low solubility in water? a) They are much denser than water. b) They cannot form hydrogen bonds to water. (3) They are much larger than water. Cl) They have strong mutual attractions. 14 GKB-2009ExamQuestions 51). Consider a dialysis procedure in which an aqueous solution is separated from pure water by a membrane that is permeable to both water and solutes. Which statement is true? a) Dialysis cannot separate molecules based upon their relative sizes. b) The membrane can be fine-tuned to selectively allow large molecules instead of smaller molecules to diffuse through it. c) The random movement of molecules, called diffusion, proceeds only until the concentration is the same on each side of the dialysis membrane. d) The tendency of solutes to diffuse from a region of high concentration to a region of lower concentration is thermodynamically favored. 52). The pK of acetic acid is 4.76. Which statement is true at pH 5.0? a) [A'] > [HA] b) [A'] >> [HA] C) [A'] = [HA] d) [A'] < [HA] 53). At the first horizontal inflection point in the titration curve of phosphoric acid, which statement is true? a) [H2P04—] = [HP042-] b) [H3PO4] = [H2P04'] C) [H3P04] > [H2P04_] d) [H2P04'] > [HPO4'] 54). Which is the weakest interaction? a) An ionic interaction between a carboxylic acid and an amine. b) A hydrogen bond between two water molecules. c) A van der Waals interaction between two methyl groups. d) A covalent bond between the 0 and H atoms of water. 55). The pH at the midpoint of an acid/base titration is: a) equal to the pK of the corresponding acid b) equal to the pK of the correSponding base c) equal to 14 minus the pK of the corresponding acid d) equal to 14 plus the pK of the corresponding base e) none of the above 56). If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain? a) 50 ,3 b) 150 ' 15 R GKB-ZOOQExamQuestions c) 75 d) 25 57). Nucleotides contain phosphate groups bonded to the: a) C3‘ or C5' atoms b) C3 or C3‘ atoms c) C5 or N9 atoms cl) C3 or N9 atoms e) none of the above 58). The most common tautomeric form of the purine and pyrimidine bases in nucleic acids is the: a) enol form b) imino form c) keto form d) ester form e) none of the above 59). DNA sequencing using the Sanger method requires: a) template, primer, DNA polymerase, mRNA, dNTPs, ddNTP b) template, primer, DNA polymerase, dNTPs, ddNTP c) template, primer, DNA polymerase, rRNA, dNTPs, ddNTP d) template, primer, DNA polymerase, mRNA, dNTPs e) none of the above 60). By convention, the sequence of nucleotide residues in a nucleic acid is written starting with the end. a) left to right; 5‘ b) right to left; 5' c) right to left; 3' d) top to bottom; 3' e) left to right; 3' 61). Free nucleotides are almost always associated with in cells. a) fatty acids b) Mg2+ counterions c) CI' counterions 16 GKB-2009ExamQuestions d) proteins e) cholesterol 62). Transfer RNA molecules are involved in: a) translation b) transcription c) gene shuffling d) recombination e) duplication 63). Which one of the following sequences of five amino acids would most likely be located in the interior of a globular soluble protein? a) Glu-Asn-Ser-Thr-Gln b) Tyr-Phe—GIu-Asn-Leu c) Val-Ala-VaI-Glu—Val cl) Met-Cys—Pro-His-Tyr e) Met—Phe—Pro—Ile—Leu 64). At pH 7, arginine (sz are e—carboxylate 1.82, int-amino 8.99, guanidino 12.48) would be charged as follows: a) 0 m-carboxylate, 0 lat-amino, +1 guanidino, +1 net charge b) +1 u-carboxylate, 0 m-amino, -1 guanidino, 0 net charge c) -1 m-carboxylate, 0 e-amino, +1 guanidino, 0 net charge cl) —1 ol—carboxylate, +1 u-amino, +1 guanidino, +1 net charge e) +1 u-carboxylate, —1 cat-amino, -1 guanidino, —1 net charge 32). The peptide shown has the amino acid sequence: 0:0 I on ci'H2 H 0 CH: H 0 OH, H o l. 34 . .I. a: . .l l H— CH CH 1 H” \N/ \c/ \CH” ‘14" ‘0’ \CH/ \0- H 4.. a. a: 4.. l a! . CH / /' 9 CH3\CH3 CH3 \CH2 l l CH2 CH3 | of” CH, l *NI-lz a) Thr—Asp-Leu-Gln-Arg b) Val-Asp-Ile-GIu—Arg 17 GKB—2009ExamQuestions c) Val-Ser-IIe-Glu-Lys d) Lys—Glu-Ile-Ser-Val e) Ade-Gua-Cyt-Thy-Ura 65). The salting in of proteins can be explained by: a) proteins attracting primarily salt anions. b) proteins attracting primarily salt cations. c) releasing hydrophobic proteins from nonpolar tissue environments. d) hydration of the salt ions reducing solubility of proteins. e) salt counter-ions reducing electrostatic attractions between protein molecules. 66). Which physical characteristic is not commonly used in protein separation? as)» charge bi) size 15;) stereochemistry idx) polarity é) solubility 18 ...
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