Exam_1_2003_Spring

Exam_1_2003_Spring - BCH 4024 INTRODUCTION TO BIOCHEMISTRY...

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Unformatted text preview: BCH 4024 INTRODUCTION TO BIOCHEMISTRY AND MOLECULAR BIOLOGY DR. R. DONALD ALLISON FIRST EXAMINATION: FEBRUARY 13, 2003 Please PRINT your last name neatly on the answer sheet, followed by your initials. Fill in your Social Security Number legibly and accurately. Care has to be exercised in doing this. If you are unsure of how to properly encode your number and name onto the answer sheet, ask a proctor for assistance. If the answer sheet is filled in incorrectly, your sheet will be lost in the computer! Mark the most nearly correct answer on the sheet by completely filling-in the apprOpriate box with the correct type of pencil. If you do not have the correct type of pencil, one can be provided for you. Each question is worth two points. You have two hours to work on the examination. At the end of that time, all answer sheets will be collected. If you need assistance, PLEASE RAISE YOUR HAND AND WAIT IN YOUR SEATF OR A PROCTOR. AT NO TIME SHOULD YOU RAISE YOUR EXAMINATION OR YOUR ANSWER SHEET OFF OF YOUR DESK! Before the start ofthe examination, remove all notes, books, etc., from your desk. Please have at least one seat between you and any classmate. DO NOT OPEN THE EXAMINATION UNTIL YOU ARE TOLD TO DO SO BY THE PROCTOR. Take a breath, relax, and do your best. Divalent cations are found in all living organisms. Which of the following specific divalent cations is found in all living organisms? A) so“ .1321. W“ K C) Mg2+ D") Ni2+ E) Sn2+ Which of the following bond energies is significantly larger than the others? A)_/Si—O "13) 0-0 C) or: D) C—H E) N—C The electrostatic attraction (that is, the bond energy) between opposite charges in a biomolecule (such as a protein) is greatly affected by the microenvironment around those charges. Which of the following would you expect to be true? A) Raising the temperature would tend to decrease the distance (and increase the bond \ \energy) between the opposite charges. B) “ Lowering the dielectric constant can result in a decrease in the distance between the ’two charges. C) Raising the surface tension of the microenvironment will decrease the bond energy. D) An increase in the overall osmotic pressure will lower the bond energy. E) None of the above The sodium chloride concentration in human blood is roughly 0.15 M. Thus, human blood will have compared to pure water. A) lower osmotic pressure B) higher vapor pressure ,C) elevated freezing point D); higher boiling point E) (any two of the above) 5) 6) ./ _ B), The pH of the solution is 490. Which of the following statements is true? A) The pKa of water (i.e, pKw) is seven (7). '13)“ Water is a strong Lewis acid. " C),/ Water is a proton acceptor in an aqueous solution of acetic acid. D) Zwitteiions of amino acids can neither give nor take up protons. E) If the pH of a solution of acetic acid is equal or close to the pKa value of acetic acid, then the concentration of acetate must be significantly larger than the concentration of the conjugate acid. To a 100 mL solution of 0.4 M isoleucine hydrochloride (i.e., the totally protonated form of isoleucine) is added 32 mL of 1.0 M NaOH. What is the final pH value? (Assume isoleucine has pKa values of 2.32 and 9.76.) A) 1.72 B) 2.22 5C)? 2.92 D) 9.16 E) 10.36 Lactic acid (CH3 CH(OH)COOH) has a pKa value of 3.90. If the conjugate base (i.e., the anionic form) had a concentration ten times larger than the concentration of totally protonated form of lactic acid, which of the following would be true? A) A determination of pH could not be made until the concentration and/or volume is . provided. C) Lactate will be a strong buffer if the concentration was greater than ten times. D) The pH of the solution is 2.90. E) None of the above Which of the following is true concerning the pKa of the side chain of a lysine that is part of the amino acid sequence of a protein? A): The lysine side chain can form a salt bridge with a histidine side chain. ’13) The pKa of the side chain will be lower if the microenvironrnent surrounding the side chain is less polar than water. C) The lysine side chain will be a good buffer at pH 5.8. D) The lysine side chain can act as a good Lewis acid at pH 7.0. E) None of the above are true. The amino acids listed below refer to questions 9 through 14. A) sarcosine B) cysteine C) arginine D) glycine E) proline Which of the above amino acids best fits the following description? 9. has the least conformational constraint on the fold of a protein’s main-chain ("l 10. could form a salt bridge with aspartic acid L 1 1. is not found in proteins i l j}- 12. you would least expect to find in an a—helix l a" c -" 5}: l3. side-chain most likely undergoes oxidation '2" I? 14. side-chain forms a covalent bond with the protein main-chain 1.4, ’3 Refer to the diagram below to answer questions 15 through 19: o 0' o NH2 \\ / \\ / c c o l I CH2 A CH2 1 / a c C' a \CqH/ O\ NH/ H\COO' | \ CH7 B @1- SH 15. Which of the following statements is true about the main-chain torsion angle between the N — Cot bond (indicated by the arrow A): A) It is termed the alpha angle. B),__ 1t is termed the beta angle. «’It is termed the phi angle. D) It is termed the psi angle. E) It is termed the omega angle. 16. Which of the following statements is true about the main-chain torsion angle between the C 0!. — C ’ bond (indicated by the arrow B)? a) It is termed the alpha angle b) It is termed the beta angle. p) It is termed the phi angle. Cd_)_:-'lt is termed the psi angle. c) It is termed the omega angle. 17. What amino acid side-chain is located at position I? a) tyrosine b) lysine arginine id) C'aspartic acid " e1) glutamic acid 18. What amino acid side-chain is located at position II? 7 a); cysteine serine c) methionine d) leucine e) threonine 19. What amino acid side-chain is located at position III? a) serine b) glutamine we} methionine ;: asp aragine e) threonine _———-————-—____——_—___—__ 20. Which of the following amino acids is not charged? i a)/)isoleucine l3) arginine c) lysine d) glutamic acid e) aspartic acid 21. Considering only their side chain, which of these amino acids is the most basic? a) histidine b) leucine EL alanine (ti/)jlysine he) isoleucine 22. Which amino acid are you mostly likely to find in a tight turn of a folded protein? a) tryptophan b) phenylalanine c) proline d) tyrosine e glycine F“. 23. All of the following general statements are true of the peptide bond of the main-chain of a protein, except for one statement. Which statement is not true? Peptide bonds are essentially planar. : I b); The peptide bond nearly always has the cis configuration except sometimes with proline ,1 / residues which can have a trans configuration 33“ _ a) c) The peptide bond has some double bond character (40%) due to resonance which occurs with Cr amides. d) The peptide bond torsion angle is referred to as omega. I a l t, ' x "5)“; The peptide bond is longer than what is general seen in a C-N‘ bond f l \_. 34. Which of these terms best defines a secondary structural element in a protein? a) the peptide bonds b) the hydrophobic interactions fol the disulfide bonds (’dLIthe phi, psi torsion angles "6) van der Waals interactions 25. Which of the following statements is not true about ion exchange chromatography? a) The amino acids lysine and arginine have side-chain groups that are ionizable. At a pH = pl of a protein, the protein will not bind to an ion exchange resin. At a pH above its pl, a protein will have a net negative charge. d) Negatively charged exchangers bind positively charge ions. (er) EAt a pH below its p1, a protein will have a net negative charge. \, / . 26. 27. 28. 29. Which of the following statements is not true about gel filtration chromatography? A) "k; <: E) Separation of proteins occurs based on their size. Separation of proteins is due to exclusion or inclusion from a gel matrix. Proteins elute from the column in order of decreasing molecular weight. Proteins elute from the column in order of increasing molecular weight. All of the above are true. The reaction rate of a particular reaction is accelerated by the presence of an enzyme. This acceleration is due primarily to: A) B) C) 12).. Te :-: an increase in AH a decrease in AG a decrease in AGo an increase in AH and a decrease in AS a decrease in AGactivan-on A progress curve is a plot of vs. A) B). (e); D) E) velocity; time enzyme concentration; time product concentration; time substrate concentration; enzyme concentration velocity; substrate concentration An enzyme has recently been isolated from a patient’s liver and has been found to obey Michaelis—Menten kinetics. The Vmax value was found to be 14.8 umoles per minute, and velocity was reported to be 9.4 umoles/min when the substrate concentration was 8.8 mM. What is the value of the Michaelis constant? A) 1.57 mM 3.96 mM' f’ (3),: 506 mM "’b) 7.40 mM E) 13.86 mM (MEGA/C, PLGT UTE?) X 30. What is the slope of the line below? A? QUE an m/ was Discs/83%;), A) 'Vmax B -Km ) 'Vmax/'Km ) ‘Km/Vmax E) 'Vmame \e 31. A certain enzyme acts on a number of sugars. From the kinetic parameters below, which is the most effective and efficient substrate for this enzyme? sugars K5, Vmax ribose 50 mM 1 umol/min mannose 1 mM 3 umol/rnin glucose 10 mM 5‘ umollrnin sucrose 5 mM 20 umol/min galactose 20 mM 40 umol/min A) ribose B) mannose C)» glucose sucrose E) galactose 32. An inhibitor is found that binds to both to the free enzyme and the enzyme-substrate binary complex. The inhibitor is most likely A) irreversible [53.1 _ competitive '\ C) .' noncompetitive uncompetitive E) feedback Which of the following plots would be observed for an uncompetitive inhibitor? The solid line represents data in the absence of the inhibitor. The dashed line is in the presence of the inhibitor. 34. The effectiveness of an inhibitor or pharmaceutical is gauged by the magnitude of the Ki ' value. For the example below, how would you graphically determine the Ki value? I +I/ A) Replot the inhibitor concentration as a fimction of velocity. B) Replot 1/V as a function of [S]. C) Replot the slopes as a function of the inhibitor concentration. D) Replot the vertical intercepts as a function of the inhibitor concentration. E) none of the above 35. Which of the following best describes the steady-state assumption in the derivation of the rate expression for a one-substrate one—product enzyme? é) d[P]/dt = O (a) d[EX]/dt = 0 0) [Ea] = [E] + {BK} D) [P]o = 0 E) none of the above 36. An inactive precursor of an enzyme is frequently called 2101): A) isozyme B) hysteretic protein .C.) allosteric protein / 4. u, D? zymogen E) inducible protein 37. Two enzymes catalyze the same reaction, have the same Vnm values, but have different Km values. Using the answers in problem 36, the individual enzymes are likely —A* n, ' f l 38. 39. 40. 41. 42. A two—substrate, two—product enzyme utilizes an ordered bi bi kinetic mechanism: 5 ,1? A+E Eaémgfizflogmggm _..3. T.- Which of the following would be true? A) A competitive inhibitor will bind to EAB? B An uncompetitive inhibitor will bind to E. 7 If P binds to EA, the resulting complex, BAP, is called an abortive complex. D Abortive complexes can only form in random mechanisms. E) In the reverse reaction, EQ is an abortive complex. Hysteretic enzymes involve: A) binding of substrates to more than one binding site. B enzymes displaying hyperbolic kinetics @ enzymes exhibiting a slow conformational change D) only negative cooperativity E) none of the above Which of the following vitamins is associated with a coenZy‘me participating in amino transfer reactions? A thiamin pyridoxine C) pantothenate D) riboflavin E) biotin Which of the vitamins in problem 40 binds very tightly to avidin? A) thiamin B) pyridoxine C) pantothenate D riboflavin biotin The Wemicke—Korsakoff Syndrome is associated with a deficiency of: A) riboflavin B) tocopherol C ascorbate ? D) thiamin E) pantothenate 43. Extrinsic factor is a protein associated with the transport of: A) vitamin B Vitamin B12 C) vitamin C D) folic acid E) lipoic acid 44. Adenylate kinase ("AL uses phosphocreatine to generate ATP. \ B); has a AG“ value of O. C) reacts AMP with ADP. D) interconverts ATP and GTP E) is located in the cytosol. 45. Below is a table from your notes (and your textbook). It represents the AG“ values for the reactions ROP032” + H20 e R—OH + HOP032' Use the table below to determine the AG‘“ value for: phosphocreatine + ADP = creatine + ATP R—OPng' phosphoenolpyruvate —61.9 kJ/mol phosphocreatine —43. 1 pyrophosphate —3 3 ATP —30.5 ADP -30.5 glucose— 1 -phosphate —20.9 AMP ~ 1 4.2 glucose-é—phosphate —l 3 .8 (HINT: Recall that when a reaction is written in the reverse direction, the AG“ value will be exactly the same, except with the opposite sign.) A) -31.4 kJ/rnol ,_B)._—28.9 kJ/mol (MET-412.6 kJ/mol D) +12.6 kJ/mol E) +31.4 kJ/mol 46. Which of the following is a pentose‘? A) mannose B) glyc eraldehyde Q fructose RD.» ribose E) cellobiose 47. Which of the following is the thermodynamically favored form of D-glucose at room temperature in aqueous solution: (Ho A OH > 0H 0H CHZOH CHon 8’) 0 0H \ OH Ho H oH cnzo C) [/0 Ho 0H 0H cilon j) > Ho O 0H 6H 0H CHZOH E ) 0 0H “0 6H 48. Which of the following is true of two epimers? A) They are always anomers of each other. B) They rotate the plane of polarized light in equal but opposite directions. (/5) They have different chemical and physical properties. "‘D) Both cannot exist in a cell at the same time. E) Two of the above are true. 49. Which of the following carbons, in a sugar you have never seen, is the reducing carbon? @ J Hoch’g “HQ/0H o (/79 0/7Z @ “'9 0H @ H0 H /’ @ 014 A) 1 B) 2 C) 3 (D)? 4 ‘13)“ 5 50. Which of the following disaccharides contains galactose as one of its sugars? g) mannose tj AB);- lactose f C) sucrose D) gentiobiose E) cellobiose ...
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Exam_1_2003_Spring - BCH 4024 INTRODUCTION TO BIOCHEMISTRY...

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