CH_369_Spring_2010_Exam_1_Key

CH_369_Spring_2010_Exam_1_Key - Nome Edfl |D CHEMISTRY 369...

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Unformatted text preview: Nome Edfl |D# CHEMISTRY 369 Spring 2m © Dr. G. Barrie Kitto EXAM 1 NOTE : Multiple Choice Questions are 2 points each Written Answer Questions are 10 points each. Please also clearly print your name on the back of the exam. Multiple Choice : 60 Written Answer l 6 2 CT 4 ll , “TD $ TOTAL POINTS \QC‘ Multiple Choice Questions (2 points each) 1. Which of the following amino acids can form a disulfide bond? a. Lysine b. Methionine Cysteine 'vd‘. Threonine e. Serine 2. Which of the following amino acids has a basic side chain? a. Asparagine b. Aspartate . Tryptophan Arginine e. Glutamine 3. This molecule is classified as a: o O_ ; /r~4 > _ __ a / NH 0 P‘ &0 HC\ I A / 0 “CH2 0 N M NH. [/ \ I ~ HC CH \ I Hc ~ CH l I OH OH 6 Nucleotide b Nucleoside c Deoxynucleotide d. Deoxynucleoside e Nucleic acid 4. Name the base in this molecule: 0 0- u I ‘ . _ __ // NH o—r—Iafio HC\ I X / 0—CH2 N N NH., Hc CH \ I Hc -— CH I I OH OH 3. Adenine @ Guanine c. Cytosine cl. Thymine e. Uracil + I I \k +_ l I 5. What is the net charge of the peptide Ala—Asp-Arg-PtQ-Glu-bln-Ser at pH 7? a. -2 -1 c. 0 d. 1 e. 2 6. What is the major buffer system inside of cells? a. Acetate b. Citrate c. Succinate d. Bicarbonate Phosphate 7. In a hypothetical buffer system with a pKa of 9, what is the concentration of the conjugate base in a 1.0 M solution at pH 5? a. 10-6 M b. 10-5 M 6 10-4 M d. 1 M e. 0 M 8. The terms a helix and B pleated sheet describe a protein’s: a. Primary structure. 63 Secondary structure. c. Tertiary structure. d. Quaternary structure. e. Quinary structure. 9. Valine is a(n) amino acid. a. Aromatic @ Hydrophobic c. Polar d. Charged e. Both a and b 10. The hydrophobic effect shown, for example, in the aggregation of oil droplets in water is driven by: a. hydrogen bonding. b. Van der Waals interactions. c. London Dispersion forces. d. enthalpy. entropy. 11. Formation of a peptide bond is a(n) reaction. a. Oxidation b. Reduction c. Hydration d. V Dehydration ‘ e. Electrostatic 12. What is the concentration of H30+ in water at pH 7? a. OM b. 1014M @10'7M "6. MW e. 7M 13. 14. 15. 16. 17. 18. The trace (also known as transition state) elements are critical in the function of some a. b. C, H, O, N, P, 5; Proteins Mg, Mn, Zn, N, P; Nucleic acids . C, O, H, N, P; Carbohydrates e. Mn, Fe, Co, Ni, Cu; Proteins Cr, Fe, Cu, Zn, S, Cd; Nucleic acids Which of the following molecules form long linear polymers? 3. b. c. cl. Amino acids Nucleic acids Lipids Carbohydrates ® Both a and b Which of the following bonds made by water are critical in dissolving polar molecules? a. b. c. Covalent, Ionic, Hydrogen, Van der Waals Covalent and Van der Waals Hydrogen and London dispersion forces ydrogen and Ionic ‘Q‘, oth b and c At what pH would the R group of arginine act as a good hydrogen donor given that the pKa ofthe R group is 12.5? a. b. c. d. 5 14 10 Both a and b l® Both aandc Acid—base reactions are fast in water because: a. water readily ionizes into H and OH. @ of proton jumping in water networks. c. d. e. water is amphiphilic. micelles form in water. none of the above. For acetic acid, which species dominates below one pH unit of the pK and one pH unit above the pK? @ CH3COOH and CH3Coo‘, respectively b. c. d. e. CH3COOH dominates at both conditions CH3COO' and CH3COOH, respectively CH3COO‘ dominates at both conditions None of the above 19. 20. 21. 22. 23. An increase in pH from 7.4 to 12.4 results in the decrease of the H ion concentration from 4.0 x 10‘8 M to ? a. 4.0 x 10‘9 M b. 7.0 x 10'8 M 4.0 x 10'13 M d. 7.0 x 10'11 M e. None of the above The secondary structure of proteins and the helical structure of DNA have what in common? a. Both have a negatively charged backbone. b. Both have a major and minor groove. c. Both have the same building blocks. H-bonds are critical to their structures. e. None of the above Which of the following double-stranded pieces of DNA would have the highest Tm (only the single strand sequence given)? .a. AAAAAAAAAAAA Q) GGGGGGGGGGGG c. AAAGGAAGGAAG d. TTGGAATlTTAT e. CCCCCTlTTTAA Pyrimidines are found in: a. DNA. b. RNA. c. proteins. d. lipids. @both a and b. Which two chemical groups ofthe protein backbone are able to H-bond? a. Alpha-carbon and the amide group (9 The carbonyl and the amide groups c. The sulfhydryl and hydroxyl groups d. The amino and carbonyl groups e. The amido and sulfhydryl groups 24. 25. 27. 28. if" 26. The side chains of and are able to form ionic interactions at a pH of 8.0. a. Glu and Arg b. Asp and Arg c. Asp and Lys d. Glu and Lys All of the above. Which amino acid is likely to be found at the center of a globular protein (away from water)? 3. Val b. He c. Trp d. Phe @All of the above. Glycine is unlike the remaining 19 amino acids with respect to: a. charge. @ chirality c. molecular weight. d. all of the above. Q3): both b and c. Only in eukaryotes is DNA: a. highly charged. it; associated with histones. c. naked. d. denatured. e. in the Z-form. At physiological pH, the side chain of which amino acid can be found in both the basic and acidic form? a. Lysine b. Aspartic c. Tyrosine @ Histidine e. Cysteine 29. Polylysine is a random coil when the pH is less than 11, while it forma an alpha helix if the pH is raised to greater than pH 12. Which of the following explains this phenomenon? a. The e-NH- group is negatively charged above pH 12 and provides stability in an alpha helix. b. The positive charge on the E-NH3+ group provides stability for this helical arrangement. @ The e-NH; groups are titrated to produce neutral —NH2 groups that eliminate electrostatic repulsion between the R groups that were present in neutral pH. d. The high concentration of OH" ions in solution at pH 12 reduces the effective positive charges on the e-NH3+ groups and results in less electrostatic repulsion between the groups. 69 Which of the following intermolecular interactions is the weakest? a. Ionic b. Hydrogen bonding c. London dispersion forces ‘7, d Van der Waals “Jaw (3. lug e. Covalent Written Answer Questions (40 Points) 1. a. (3 points) Many of the biomolecules found inside human cells are present in very small quantities. Fill in the blanks below to indicate the molar relationships e.g,, millimolar = 10 '3 M. ' ..4 l micro = lo q M nano = l0 . m I -1; , plCO = 30 l b. (3 points) Many of the properties of biomolecules depend upon the sequence of the building blocks in the polymer. Even though the number of types of building blocks may be small, the number of different sequences that can be generated is extremely large. For example, calculate the number of different short polypeptides seven amino acids in length that could be synthesized even if only 15, instead ofthe usual 20, were available. Show your work. A 7 .mi Psalms l5 Possible mvhj‘flf't‘adfls ‘ l‘t A AA l “l will? “m AM Ms AM M? £15] X waESB xflfixfiDSl ‘0511051 a . : Nil/($53) 575 2. a. (4 points) In water, a single water molecule can interact through hydrogen bonding with as many as four other water molecules. illustrate a water molecule forming hydrogen bonds with 4 other water molecules. 0 0 / \, ll/ \H. g- ,H ‘l «11/ V\, H /0\ H ;s* Si O. ‘Q h/ Xi H/ \a 8 b. a. b. (5 points) Define pKa and show its relationship to pH with the Henderson- Hasselbalch equation. ' Pl‘q ‘ ‘ l“) K“ . t. inulKH/flflt {7 (3V), H gr“: ,1. 5 «jg/M 2a.; ‘4“ < (t #0“ (“staid M=$Wwv*Jr vwwwi . ,.A “ .6tfifin- i w PM: PM 3 UV): [HA1 (fit/m W K 6 Lump} . {A11 3394;.» 0‘ [HA3 :3 3 r o . ‘ m“ will: PM“ 9“ PK“ * ' f3 [HA3 9.; M. (3 points) Several biological processes require the formation of DNA/RNA hybrid regions. Given the DNA sequence below, write the RNA sequence that could form a DNA/RNA hybrid. _5’ A-A-G-C-T-C-G-T _ 3' EBUCGAGCAEI DNA RNA (2 points) What are the stabilizing forces for the formation of such double- stranded regions? 0 Qgill‘x Bowlimc) beta/zen LONV} 50668 ~ v. ’% wwflh Q7 \le dex Wmlé 5+“l‘m‘3 ‘V‘MM‘ M bases c. (5 point ) Draw thedetailed structure of the following dB/ufltg—Mstrandedtpjece of RNA. In ' ate the details of the hydrogen bonding. ’A 5' 3' I l A U l I C G / I I on 0:, A Rdwsa ['2 oil) 3’ 5*: "o" 2.» Phosflnocliesla Bowls ‘ “H2;"-i.o\ O AKHPotfotllel “{rqv‘a‘e’m N N ' " AW\ 0 (IV-0, H) 9mm GE bqwbjw £305 . ‘ 5 . wv‘ 0‘ / <14 ‘ o 0‘ ‘3) “74”?” WAS 9” " 9" 05F0 c, 0 p” w H H a «‘0 \ O . O a“ N IOPOL‘ d. (3 points) In dideoxy DNA sequencing, what is the role of: i. the dideoxy nucleotide? Loxng 2/ OH group necess‘om7 ’F‘or qolol'rlion a? subyejwehi mac/80+.‘olgsl 5‘” hL JFUV‘MWS 67WH/ms‘ laan inmparrckm {)(odlwce§ shawls 0F vou’imlyle Ignj+k ) Why) dam £9 resolved 6v) deol—{o‘olxore/SGS’ 10 3. ii. theadded DNAponmerase? I K DNA polyvchwe/ Ccfi’a\\7m9 ’HAIC DIAAAT'W‘ 05: ' nucleafiaclcs 0“ “ll/UL growling {74fan LG\0V\5%OVD _ iii. Why was the incorporation of a very heat stable polymerase into the protocol important? m DNA 35 male; +1? “wave Amman, 50 01 Wfi‘l’ 5+1”: Fowwo‘fie 76 clue W'Hlflqugl “Wis haw/7313 quA fem:n ’anc'h'ana’] {FM WmWfle C7cle5' Gwyn” L213 4 (qulaz poem/0,2 We ma) Tia WWW” WW We 1% it crime! (NF-Jar €ch S‘I'Ep . (4 points) The hydrogen bonds helping to stabilize the alpha helix in proteins involves which functional group? Carlm‘nvl W oxwxéole, In pleated sheets, the corresponding functional groups are W 0m: ole CWBDA") l 11 b. (3 points) Fill in the three-letter code for each of the following amino acids: (200' (100' .C00' A) p B) l C) — - .. + HaN-(ll H ¥3N $ H H3N_c|..H OH; I C'H . l “*2 I.z / C CH3 gH * l l ” M NH ll’ “ \C/ D) coo' E) Coo- F) H '* l HgN—cl—H fi3N_C‘-H Cloo ' + Ci”?- CI’HI C‘H C l o4 ‘MHZ g”- H —7——0H C‘Hg CH3 A: 1'6 3: qu C: D= ASK E: F: c. (5 points) Draw the structure of the following peptide, indicating the N-terminus, the C-terminus, and the charges on the ionizable groups as they would be at pH 7. Asp—Trp—Pro o 9 H + l’,’ u 7 l' N a C//0 “3” i “ ‘ k) \° cm, CH1 (( ' tern/uan 12 ...
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This note was uploaded on 05/23/2011 for the course BIO 1402 taught by Professor Kitto during the Spring '11 term at University of Texas.

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CH_369_Spring_2010_Exam_1_Key - Nome Edfl |D CHEMISTRY 369...

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