BCHS 3304/ Exam I. September 26,

Transcription

1 Name: 5.5.# BCHS 3304/ Exam I September 26, Instructions: 1. There are 13 pages to this exam. Count pages prior to beginning exam. You may use the back pages of the exam as scratch paper. 2. This is a Scantron exam. All answers should be transferred to a scantron sheet using a #2 pencil. 3. Write your name in the appropriate box marked NAME on the front and the back side of the Scantron sheet. If your name is not clearly legible, you will be awarded 0 points for this exam. 4. Write your social security number next to your name on the back side of the scantron sheet. If your social security # is not clearly legible, you will be awarded 0 points for this exam. 5. Write BCHS 3304 in the box marked SUBJECT, EXAM I in the box marked TEST NO., and 26/09/02 in the box marked DATE. 6. Answer all questions. 7. When finished, turn in complete Scantron sheet and the copy of the exam to your instructor Questions 1-10: True or Faulse? Answer A if the following statement is True or B if the following statement is False 1. The skeletal models show only the molecular framework. 2. In a hydrogen bond, an atom is shared by two hydrogen atoms. 3. Water is a non-polar molecule.

2 4. All twenty L amino acids found in proteins have similar hydrogen-bond capabilities. 5. Frederick Sanger determined the amino acid sequence of insulin, showing that a protein has a precisely defined amino acid sequence. 6. Supersecondary structure in proteins refers to clusters os secondary structure. 7. Cyanogen bromide is a protease which cleaves after just one specific residue. 8. NMR spectroscopy can reveal the structure of proteins in crystals. 9. The distal histidine near the heme of hemoglobins is designated E7. 10.The oxygen affinity of myoglobin is regulated by organic phosphate BPG. Questions 11-50: Select the correct answer 11.Which of the following is not a feature of the a-helix <> a. the axial distance between adjacent amino acids is 2.5 A b. the side chains extend outward in a helical array c. there are 3.6 amino acid residues per turn of helix d. the helix is stabilized by hydrogen bonds e. all the main-chain CO and NH groups are hydrogen bonded 12. Most enzyme-catalyzed reactions occur in a. picoseconds b. nanoseconds c. microseconds d. milliseconds e. seconds 13. In a hydrogen bond,

3 a. A hydrogen atom is shared by two other atoms b. A hydrogen atom is shared by two carbon atoms c. The typical hydrogen-bond length is 4.2 A d. A hydrogen is covalently linked to two other atoms e. The hydrogen and the other atoms of the bond are always colinear 14.Name the following amino acid coo- I +H N-C-H 3 I CH I 2 C cf' "NH 2 a. Glutamate b. Aspartate c. Arginine d. Asparagine e. Methionine 15.Whichof the followingaminoacidcontainsan aromaticr group a. Tryptophan b. Leucine c. Cysteine d. Lysine e. Aspartate 16.Which of the following properties is common to a-helical and B-pleated sheet structures of proteins? a. Rodshape

4 b. Hydrogen bonds between main-chain CO and NH groups c. Axial distance between adjacent amino acid of 3.5 A d. The minimum number of participating amino acid residues is three e. The side chains extend outward in a helical array 17.Which of the following amino acids are likely to be found on the inside of a water-soluble protein? a. His b. Arg c. Asp d. Thr e. lie 18.Which of the following statements is not true? a. An acidic protein will have a pi greater than 7 b. A basic protein will have a pi greater than 7 c. The pi is the ph value at which the sum of all charges of a protein is zero d. At a ph value equal to its pi, a protein will not move in the electric field of an electrophoresis experiment e. All of the above 19.SOS-polyacrylamide gel electrophoresis and the isoelectric-focusing method for the separation of proteins have which of the following characteristics in common? Both a. Separate native gels b. Separate proteins according to their mass c. Require ph gradient d. Are carried out on supporting gel matrices e. can be used to calculate the molecular mass of a protein

5 20.Which of the following is a structural feature of myoglobin? a. All the prolines are found within a helices b. The surface of the molecule consists mainly of nonpolar residues c. Seventy-five percent of the amino acids are in a helices d. The heme group is bound on the surface of the protein e. The interior of the molecule is hollow so that it can accommodate many molecules of water 21.The structure of deoxyhemoglobin is stabilized by each of the following interactions except for a. BPGbinding b. Salt bridgesbetweenacidicand basicside chains c. Coordinationof the hemeswith the distal histidine d. Hydrophobic interactions e. Salt bridges involving N-terminal carbamates 22. If two molecules had a tenancy to associate with each other because groups on their surfaces could form hydrogen bonds, what would be the effect of putting these molecules in water? a. the interactions between the two molecules will be weakened b. the interactions between the two molecule will be stronger c. the interactions between the two molecule will not be effected d. the two molecules will form disulfide bonds with the water molecules e. the two molecules will occupy different cavities in the water 23. A red blood cell is 7 Ilm long. This is equal to, (j a. 104 Ạ b. 107 A

6 c. 7 x 104A d. 7 X 105nm e. 700 nm 24. A van der Waals bond is a. the attraction between two oppositely charged groups b. a type of electrostatic attraction c. a type hydrophobic attraction between two non-polar groups. d. an attractive force between two atoms which are 3 to 4 A apart G e. an attractive force between two atoms which are 4.3 A apart 25. Which reagent can be used to cleave a polypeptide chain adjacent to Met residues? a. Performic acid b. Dansyl chroride c. Cyanogen bromide d. ~-mercaptoethanol e. Trypsin 26. Which technique is used to separate the amino acids after hydrolysis of a polypeptide? a. Gel electrophoresis b. NMR c. Gel filtration d. Dialysis e. Saltingout 27. It would be possible for a salt bridge to form between the following two amino acid side chains: a. isoleucine and leucine

7 b. alanine.and phenylalanine c. methionine and cysteine d. histidine and glycine e. glutamic acid and Iycine 28. One cycle of Edman degradation yields a. protein cleaved at all cysteine residues b. protein cleaved at all methionine residues c. a PTH-derived amino acid that was cleaved from the C-terminus d. a PTH-derived amino acid that was cleaved from the N-terminus e. both a and b 29. The pi of the free amino acid glycine is approximately a. 2 b. 4 c. 6 d. 10 e Cysteine bonds can be reduced by a. trypsin b. iodoacetate c. performic acid d. carboxypeptidase e. cyanogen bromide 31. Which technique uses radiography techniques to detect small samples of a protein of interest? a. 20 electrophoresis b. western blotting

8 c. Circular dichroism d. X-ray crystallography e. All the above 32. The sequenceof the peptidenh2-asparagine-glutamic acid-methionineasparticacid-caah in the three-letterabbreviationis a. Asp-Glu-Met-Asx b. Asx-Glu-Mth-Asp c. Asp-Met-Glu-Asx d. Asn-Glu-Met-Asp e. Asx-Glu-Met-Asp 33. Which of the following amino acids would you expect to find in the interior of a protein tertiary structure? a. Phe b. Asn c. Thr d. Lys e. All the above 34. Which of the following conserved residues in hemoglobin is responsible for binding directly to the heme iron? a. His E7 (distal) b. Pro C2 c. Leu F4 d. His F8 (proximal) e. Phe CD1 35. Which mutation in hemoglobin results in the sickle cell phenotype? a. 136(Glu ~ Val)

9 b. ')'6 (Glu ~ Val) c. a6 (Val ~ Glu) d. a6 (Glu"""' Val) e. ~6 (Val~Glu) 36. What aminoacid sequencewill be cleavedby trypsin? a. CATFLAT b. SHPRECK c. SETFILE d. CNTDWNE e. SITDWNE 37. Which of the following amino acid labeling techniques results in the creation of a PTH-amino acid derivative? a. Ninhydrin treatment b. Dansyl/Dansyl chloride treatment c. Edman degradation d. Fluorodinitrobenzene treatment e. Fluorescaminetreatment 38. Which of the following was not an amino acid that was produced in the Urea- Miller experiment? a. Glycine b. Alanine c. Proline d. Glutamicacid e. Leucine 39. Scurvy is a. A geneticdisease

10 b. a Thalassemia disease c. a dietary collagen disease d. a collagen disease caused by regular ingestion of the seeds from the sweet pea Lathyrus odoratus e. none of the above 40.Whichof the followingdoesnot representa real hydrogenbond a. -Q-H...Qb. - Q - H... H- c. - N - H... Q - d. -N-H... N- e.-q-h...n- 41.If a polypeptide has 400 amino acid residues, what is its approximate mass? a. 4,000 b. 22,000 daltons c. 44,000 d. 44,000 daltons e. 88, The relative electrophoretic mobilities of a 30-kDa protein and a 92-kDa protein used as standards on an SDS-polyacrylamide gel are 0.80 and 0.41, respectively. What is the apparent mass of a protein having a mobility of 0.62 on this gel? a. 33 kda b. 40 kda c. 50 kda d. 62 kda e. 73 kda

11 43. If a solution of Val, Arg, Lys, Glu, Asp were run onto a cation exchange column at ph 7, which amino acid would emerge and in which order? a. Arg, Lys, Val, Glu, Asp b. Val, Glu, Asp c. Asp, Glu, Val d. Asp, Glu e. Asp, Glu, Val, Lys, Arg 44. You are working with a dimeric protein in which each monomer is composed of two large peptide linked by disulfides. Within the dimmer, one of these peptides is twice the molecular weight of the other. The smallest peptide in the monomer is 5,000 daltons. If you performed non-reducing SDS-PAGE gel electrophoresis on this dimeric protein, how many bands would appear and at what molecular weight? a. one band, at 30,000 b. one band, at 15,000 c. three bands, at 5,000, 10,000, 15,000 d. two bands, at 5,000, 10,000 e. none of the above 45. Determine the subunit composition of a protein from the following information: - molecular mass by gel filtration: 200 kda - molecular mass by SDS-PAGE: 100 kda - molecular mass by SDS-PAGE with j3-mercaproethanol:40 kda & 60 kda a. The protein contains three 60 kda subunits and one 40 kda subunit b. The protein contains one 60 kda subunit and one 40 kda subunit c. The protein contains two 60 kda subunits d. The protein contains one 200 kda subunit e. The protein contains two 60 kda subunits and two 40 kda subunits

12 46. The pitch of an a-helix (the length of the helix covered in one complete turn of the helix) is 5.4 A. given that there are 3.6 amino acid residues per complete turn of the a-helix, what is the length in millimeters of an a-helix that is 36 amino acid residue long? a X 10-6mm b. 5.4 X 10-9mm c X 10-5mm d. 5.4 X 10-6mm e. none of the above 47. You seek to derive the amino acid sequence of a purified peptide. Your research technician has performed multiple tests and presents you with the following data: Limited Carboxypeptidase A digestion: Ala Edman degradation (1 cycle): His Chymotrypsin digestion yields free Trp and Ala as well as 1 peptide comprised of Ala, Tyr, and His Elastase digestion yields a tripeptide and a dipeptide Your technician makes five predictions about the primary sequence of the peptide. Which of the following listed below best represents the unknown peptide. a. NH2-Trp-Tyr-Ala-Ala-His-COOH b. NH2-Ala-Ala-Trp-Tyr-His-COOH c. NH2-His-Ala-Tyr-Trp-Ala-COOH d. NH2-Ala-His-Tyr-Trp-His-COOH e. NH2-His-Ala-Trp-Tyr-Ala-COOH 48.Histones are proteins found in eukaryotic cell nuclei, tightly bound to DNA, which has many phosphate groups. The pi of histones is very high, about 10.8.

13 What amino acid residues must be present in letatively large numbers in histones? a. lie, Leu b. Lys,His, Arg c. Pro d. Phe,Trp e. Gly, Val, Met 49. A teenager can grow cm in a year during a "growth spurt." Assuming that the increase in height is due to vertical growth of collagen fibers (in bone), calculate the number of collagen helix turns synthesized per minute. a. 103 turns per minute b. 291 turns per minute c. 510 turns per minute d. 2,010 turns per minute e. none of the above 50.Pronini, a 100-kd hypothetical protein, is a three-stranded a-helical coiled coil. What is the length of the molecule? <- a. 700 A C' b. 110A < c. 455 A d. 15 nm e. 70,000 daltons