Practice Exam - Midterm 1
Practice Exam - Midterm 1 BCH 369
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This 13 page Bundle was uploaded by Stephanie Rebong on Sunday May 8, 2016. The Bundle belongs to BCH 369 at University of Texas at Austin taught by GRABNER, GAIL in Spring 2015. Since its upload, it has received 27 views. For similar materials see FUNDAMENTALS OF BIOCHEMISTRY in Biochemistry at University of Texas at Austin.
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Date Created: 05/08/16
Page 1 BCH 369 Exam 1 September 29, 2015 Name: __________________________________________ eID ________________ Section I (20 points): 1 point each 1. The strongest non-covalent intermolecuar forces are: A) van der Waals forces D) Dipole-dipole interactions B) London dispersion forces E) Ionic interactions C) Hydrogen bonds 2. Under what conditions would an amine group be mostly charged? A) pH = pK B) pH < pK C) pH > pK 3. Which of the following could be unicellar? A) Prokaryotes C) Either prokaryotes or eukaryotes B) Eukaryotes D) Neither prokaryotes nor eukaryotes 4. Which of the following would represent the reaction coordinate for an endergonic reaction? A) A B) B 5. Which of the following amino acids could bind to the specificity pocket of Trypsin? A) Gly B) Lys C) Asp D) Gln E) Val 6. Isozymes are __________ A) multiple enzymes that share the same catalytic function. B) enzymes that catalyze varied reactions. C) a group of enzymes that aid in anabolism (synthesis). D) enzymes that catalyze reverse reactions to those of main enzymes. Scrambled version C Page 2 7. In SDS gel electrophoresis A) proteins are separated based on their molecular weight B) only proteins with aromatic amino acids may be separated C) the largest proteins move the farthest D) all of the above 8. Which of the following is NOT an element of protein secondary structure? A) Alpha helix B) Peptide bond C) Beta sheet D) Polypeptide loop E) All of the above are elements of protein secondary structure. 9. Which of the following statements is TRUE about the way that hemoglobin and myoglobin bind oxygen? A) Hemoglobin has a linear oxygen saturation curve while myoglobin has a hyperbolic curve. B) Hemoglobin has a sigmoidal oxygen saturation curve while myoglobin has a linear. C) Hemoglobin has a hyperbolic oxygen saturation curve while myoglobin has a linear curve. D) Hemoglobin has a sigmoidal oxygen saturation curve while myoglobin has a hyperbolic curve E) None of the above is true. 10. Which of the molecules below contains a carboxylate group? (a) (b) (c) (d) A) (a) only D) (a), (c), and (d) B) (b) only E) All (a-d) C) (a) and (b) + 11. What is the [H ] for saliva (pH ~6.6)? A) 2.5 x 10 M7 B) 3.2 x 10 M C) 4.0 x 10 M D) 2.5 x 10 M E) 4.0 x 10 M 12. Which of the following assembles by association of multiple protofilaments? A) Myosin B) Actin C) Tubulin D) Keratin E) Collagen 13. Which of the following proteins contain a high percentage of a modified Pro residue? A) Keratin B) Collagen C) Tubulin D) Actin E) Myosin Scrambled version C Page 3 14. In order to find planets that may host life, Astrophysicists analyze distant solar systems using light emission spectrometry in which light is scattered through a prism and distinct spectral lines reveal the elements from which these lines are generated. If trying to find potential life-hosting worlds, which elements would you expect astrophysicists are looking for in highest abundance in these distant solar systems? A) O, Ca, Na, N, H B) O, C, N, H C) Si, N, O, Fe, H D) H, O, S, He, N 15. Which amino acid would most likely associate with the inner part of the lipid bilayer? A) V B) E C) H D) D E) K 16. The tertiary structures of myglobin,α-hemoglobin andβ-hemoglobin are nearly identical and are therefore nearly identical in primary structure. A) True B) False 17. Which of the following is not a serine protease? A) Chymotrypsin B) Trypsin C) Elastase D) Collagenase 18. What is the sign of the entropy change when dry ice sublimates? A) Positive▯ B) Negative C) No change 19. Which of the following techniques is useful in determining the primary structure of peptides? A) Ion exchange chromatography D) Edman sequencing B) X-ray crystallography E) Both C and D C) Mass spectrometry 20. Using what you have learned about acidic functional groups, which form of this compound is likely to predominate in the cell at pH 7.4? A) Pyruvic acid B) Pyruvate C) Neither will predominate -- there will be equal amounts of each Section II (62 points): 2 points each 21. Beta sheets consist of tight, right hand turns which causes the protein to fold back onto itself and allows for the characteristic hydrogen bonding. Which amino acids would likely be found at these turning points? A) E, K B) G, P C) L, I D) R, K E) S, T 22. What is the pH of a solution of 1.0 x 1NaOH? A) 4 B) 7 C) 8 D) -4 E) 14 Scrambled version C Page 4 23. What types of bonds are present in DNA? A) Peptide bonds D) Both A and B B) Phosphodiester bonds E) Both B and C C) Glycosidic bonds 24. Given the information below, which protein will migrate to the cathode at pH 8.0? Protein▯ pI Myoglobin▯ 6.8 Cytochrome c▯ 9.3 Carbonic anhydrase▯ 4.9 A) Myoglobin B) Cytochrome c C) Carbonic anhydrase 25. The enzyme that catalyzes the reaction below would be classified as a(n) A) Oxidoreductase D) Hydrolase B) Lyase E) Isomerase C) Ligase 26. Movement of the oxyanion further into the active site, where it can be preferentially bound, stabilizes the transition state of the chymotrypsin mechanism. A) True B) False 27. Calculate the ratio of imidazole to the imidazolium ion (pK 7.00) in a solution of pH 7.4 (structure below). A) 2.5 to 1 B) 1 to 2.5 C) 0.4 to 1 D) 1 to 0.4 Scrambled version C Page 5 28. The molecule shown below is a substrate for trypsin. Which bond will be hydrolyzed? A) 1 B) 2 C) 3 D) 4 29. The reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase is given below. To which class does the enzyme belong? A) Transferase D) Hydrolase B) Isomerase E) Lyase C) Oxidoreductase 30. Based on the reaction below, how would the enzyme catalyzing this reaction be classified? A) Oxidoreductase D) Ligase B) Hydrolase E) Transferase C) Lyase 31. What level of protein structure contains the information needed for proper protein folding? A) Primary B) Secondary C) Tertiary D) Quaternary E) A and B Scrambled version C Page 6 32. Enkephalin is an endogenous opioid peptide neurotransmitter. Based on the structure of the peptide at physiological pH (below), what is the sequence of the peptide? A) T-G-G-P-L B) Y-G-G-F-L C) F-G-A-Y-I D) Y-A-A-Y-I E) W-G-G-I-V 33. What is the net charge on the following peptide at pH 5? V-E-R-Y-H-A-R-M-F-Y-L A) +2 B) +1 C) 0 D) -1 E) -2 34. In the reaction mechanism of the glycolytic enzyme aldolase, an active site tyrosine residue accepts a proton from the substrate. In this form the side chain of Tyr must be _________ and it is acting as a(n) __________ catalyst. A) protonated; acid B) deprotonated; acid C) deprotonated; base D) protonated; base 35. Hexokinase undergoes a large conformational change in order to exclude water from the active site. Would chymotrypsin undergo such a change upon binding its substrate? A) Yes B) No 36. Which of the following proteins contain polypeptide chains that associate in a coiled-coil interaction? A) Actin B) Keratin C) Myosin D) Aand B E) B and C 37. You are given data that shows the ΔG of the reaction below to be approximately -31.5 kJ/mol. In the laboratory, you measure an enthalpy value of -4.3 kJ/mol and an entropy value of +73.4 J/mol. At what temperature must this reaction take place in order to reach the experimentally determinedΔG value? Phosphoenolpyruvate + ADP + P --> Pyruvate + ATP i A) 100 C B) 371 C C) 298K D) 371K E) 97K 38. How many H-bond acceptor atoms are present in the molecule below? (Note: These are individual atoms NOT groups.) A) 2 B) 3 C) 4 D) 5 E) 6 Scrambled version C Page 7 39. According to the table below, which of the listed elements would likely be the strongest H-bond acceptor? A) C B) F C) H D) N E) O 40. Rank the following compounds with increasing solubility in water. A) (a) < (d) < (c) < (b) < (e) D) (a) < (d) < (d) < (c) < (b) B) (d) < (a) < (e) < (b) < (c) E) (d) < (e) < (a) < (b) < (c) C) (d) < (e) < (a) < (c) < (b) 41. In the following reaction of succinate to form fumarate A) Succinate is oxidized and FAD is reduced D) Succinate is reduced and FAD is reduced B) Fumarate is oxidized and FAD is reduced E) Succinate is oxidized and FAD is oxidized C) Succinate is reduced and FAD is oxidized Scrambled version C Page 8 42. The structure of acetylsalicylic acid (aspirin) is shown below. Is aspirin more likely to be absorbed (pass through a lipid membrane) in the stomach (pH ~2) or in the small intestine (pH ~8)? A) Stomach C) Absorbed in both stomach and small intestine B) Small intestine 43. The following structure is an amino acid derivative found in collagen structures. Based on your knowledge of amino acid structure, what is the name of this derivative? A) Hydroxylysine D) Hydroxyproline B) Lipocysteine E) Selenocysteine C) Pyrrolysine 44. For marine mammals that spend a significant amount of time under water, retaining sufficient oxygen in muscle tissue is essential for their survival. Based on your understanding of the oxygen binding functions of myoglobin (Mb) and hemoglobin (Hb), how would you expect the ratio of Mb to Hb to compare between humans and marine mammals? A) The ratio of myoglobin to hemoglobin in humans and marine mammals would be identical. B) The ratio of myoglobin to hemoglobin would be higher in humans than in marine mammals. C) The ratio of myoglobin to hemoglobin would be higher in marine mammals than in humans. D) Not enough information to tell 45. Phosphoric acid (H PO3) h4s 3 ionizable protons (pK 2.151 pK 6.82, 2K 12.38). 3hich two phosphate species would be used to prepare a buffer solution at pH 11? A) H P3 an4 H PO 2 4- D) H P2 an4 PO 4 3- B) H P2 an4 HPO 42- E) H P3 an4 HPO 42- C) HPO 42- and PO 43- Scrambled version C Page 9 46. Why is it important that the heme prosthetic group be buried in a hydrophobic pocket in 2 -binding proteins? A) The heme group is entirely hydrophobic and therefore cannot be solvent exposed. B) O is uncharged and hydrophobic and therefore needs this type of environment in order to bind. 2 C) The heme iron is readily oxidized to Fe , which cannot bind O 2 D) The heme group would bind H O i2stead of O if 2t were solvent exposed. 47. In humans, Sporatic Fatal Insomnia (sFI) is a disease characterized by difficulty falling asleep, difficulty walking, gradual weight loss and excessive tear production. sFI rapidly progresses to the loss of consciousness and eventually death. sFI is thought to result from the aggregation of misfolded proteins in the cell. Which of the following interactions contributes the most to the aggregation of these protein structures? A) van der Waals D) disulfide B) ionic E) hydrogen bonding C) covalent 48. Bisphosphoglycerate promotes the oxy-state of hemoglobin. A) True B) False 49. Hundreds of hemoglobin variants are known, but one of the better-known variants is sickle-cell hemoglobin (Hb S). It is the aggregation of deoxy-Hb S that results in the sickling of the cell. The protozoan that causes malaria, Plasmodium falciparum, slightly decreases the pH of the red blood cells it infects. Are Plasmodium-infected cells more or less likely to undergo sickling in individuals with the Hb S variant? A) More likely B) Less likely C) Equally likely 50. What type of interactions are responsible for the characteristic strength of keratin fibers? A) van der Waals D) A and B B) Disulfide bonds E) A, B and C C) Hydrogen bonds 51. Collagen molecules contain cross-links of the amino acid side chains of A) C B) Y C) S D) K E) P Section III (18 points): 3 points each 52. Phosphoenolpyruvate donates a phosphate groups to ADP to produce pyruvate and ATP. The ΔG value for this reaction at 25 C is -63 kJ/mol and the value ofΔS is 190 J/K-mol. What is the value ofΔH and is the reaction exothermic or endothermic? A) +6.4 kJ/mol, exothermic D) +119.6 kJ/mol, endothermic B) -6.4 kJ/mol, exothermic E) -119.6 kJ/mol, exothermic C) -119.6 kJ/mol, endothermic Scrambled version C Page 10 53. One liter of 0.150 M Tris buffer (pK 8.30) is prepared and adjusted to pH 8.40. What is the pH when 2.00 mL of 3.00 M HCl is added to this buffer? A) 8.05 B) 7.05 C) 8.29 D) 8.75 E) 7.85 54. About 24 His residues in hemoglobin (Hb) are involved in binding protons produced by cellular metabolism. In this manner, Hb contributes to buffering in the blood. One important contributor is His146 on the β chain of Hb, whose side chain is in close proximity to the side chain of Asp94 in the deoxy form of Hb but not in the oxy form. What kind of interaction occurs between Asp94 and His146 in deoxy-Hb? In what way does the proximity of Asp94 alter the pK of His? A) Asp94 & His146 form a hydrogen bond; Asp94 increases the pK of His146 B) Asp94 & His146 form an ion pair; Asp94 decreases the pK of His146 C) Asp94 & His146 form an ion pair; Asp94 increases the pK of His146 D) Asp94 & His146 form an dipole-dipole pair; Asp94 decreases the pK of His146 E) Asp94 & His146 form a hydrogen bond; Asp94 decreases the pK of His146 55. Rnase A is a digestive enzyme that hydrolyzes RNA into its component nucleotides. The pK values of the catalytic His residues are 5.4 and 6.4. The first step in the mechanism is shown below. Assign the appropriate pK values. What is the pH optimum for this reaction? A) His12 pK 5.4; His119 pK 6.4; pH optimum ~5.4 B) His12 pK 6.4; His119 pK 5.4; pH optimum ~5.9 C) His12 pK 5.4; His119 pK 6.4; pH optimum ~6.4 D) His12 pK 5.4; His119 pK 6.4; pH optimum ~5.9 E) His12 pK 6.4; His119 pK 5.4; pH optimum ~5.4 Scrambled version C Page 11 56. You isolate a solution of three unknown proteins X, Y, and Z from a cell, but you wish to study each protein individually. Given the following molecular weights and isoelectric points, which would be the best method to elute ONLY protein Z FIRST from the solution? Protein▯ MW(D)▯ pI X▯ 45,000▯ 8.0 Y▯ 45,150▯ 6.3 Z▯ 44,950▯ 4.2 A) Use size exclusion chromatography to separate the proteins by molecular weight. B) Use DHEA-cellulose ion exchange chromatography beginning at pH 9.0 and gradually lower the pH to 5.2. C) Use CM-cellulose ion exchange chromatography beginning at pH 9.0 and gradually lower the pH to 5.2. D) Use CM-cellulose ion exchange chromatography beginning at pH 3.2 and gradually raise the pH to 5.2. 57. Like all equilbrium constants, the value ofK is temperature dependent. K is 1.47 x 10 -14at 30 C. W W What is "neutral" pH at this temperature? A) 7.00 B) 6.92 C) 13.8 D) 6.00 E) 14.0 Scrambled version C Page 12 Answer Key - Exam1Fa15 1. E 2. B 3. C 4. A 5. B 6. A 7. A 8. B 9. D 10. D 11. A 12. C 13. B 14. B 15. A 16. B 17. D 18. A 19. E 20. B 21. B 22. B 23. E 24. B 25. B 26. A 27. A 28. D 29. C 30. E 31. A 32. B 33. A 34. C 35. B 36. E 37. D 38. D 39. B 40. B 41. A 42. A 43. D Scrambled version C Page 13 44. C 45. C 46. C 47. A 48. B 49. A 50. D 51. D 52. B 53. C 54. C 55. D 56. D 57. B Scrambled version C
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