203f02_e2_key

203f02_e2_key - Chemistry 203 Lg(Fall 02 Exam#2 La N...

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Unformatted text preview: Chemistry 203 Lg (Fall 02) Exam #2 La N October 22, 2002; 11:00-11:50 am. Firs Name: Prof. Charles E. McKenna So a1 Secu 'ty INITIAL OF LAST NAME Pleas a 0 not open this exam until you ,n e told to do so. Write leginy to avoid co ‘ sion. GOOD LUCK v ’ Maximum ‘ V Question # Points ‘/ Score Grader - { I will observe the rules of Academic int::%y~{\hile taking this exam. 1. Student Signature Circle the most nearly correct answer. (4 Pts.) (1) Including non-bonding electron pairs, a correct structure is: H — : fi—C—O—CHs H H — :"F—cL—B CH3 | .. H H 6 :Z'f—clz—B—Cm 1. :fi : NH3+>/ C02- (2) In amino acids H I’R the R part could be: — Non-polar like — Ionic, like —CH2CO{ or —(CH2)4NH3” — Polar, like —CH20H - 0 Any of the above Which of the following molecules is chiral? CI An example of a drug that works by competitive inhibition of a bacterial enzyme is: penicillin sulfa aspirin AZT Catalysis by enzymes: Can distinguish two substrates which differ only as image and mirror—image (chiral) Requires special ionic, polar and or hydrophobic interactions between the enzyme and the substrate Is involved in the multiplication of HIV virus All of the above is true The formal charges in the molecule to the right are: C+ N— ’ T T C zero N zero I C zero N+ V a H_— C—N_—H C— N zero l l H H (8) The number of electrons on a helium (He) atom available for bonding is: 0 1 2 4 The compound shown below contains: 0 H II I ll H—C—T—C— -—CH3 H Both an ether and an amine group Both an aldehyde and an ester group Both an amide and an acid group Both an alkene and an alcohol group A molecule: Is formed from 2 or more atoms Consists of atoms joined by 2-electron bonds Has a molecular weight consisting of the sum of the weights of its atoms All of the above is true How many different dipeptides HzN-aal-aaz-COZH are possible, assuming aa11 could be any of the common amino acids? 4 64 400 8000 Primary vs. tertiary structure of a protein: Primary = amino acid sequence, tertiary = overall conformation or shape in 3D Primary = repeating coils or sheets, tertiary = random structure Primary = overall conformation in 3D, tertiary = grouping of > 2 protein molecules Primary amino acid sequence, tertiary rrepeating coil or sheet f Li is mixed with fluorine gas. Result? No reaction Covalent (shared bond) compound, Li-F Ionic salt, LiGFG) Ionic salt, Li©Fe Which among the following has the most polar covalent bond: HO—CH3 - H3C-CH3 o=o H—CH3 In the reaction H2 + HzC=CH2 + Pd/C —> H3C-CH3 + Pd/C, the total number of new bonds when the product forms on release from the surface of the catalyst is: 2 3 4 0 Myoglobin, the O2 storage protein of muscle (shown below): Has several extensive “[3 sheet” regions Has no extensive a-helical regions Requires the help of an Fe atom to bind the 02 Has a carboxyl group terminating each end 5 Van der Waals (like-like) bond — Hydrogen bond — Ionic bond — Covalent S—S bond @ The weakest secondary type of individual bond found in proteins is: (17) The picture below represents: electron(s) = First Row, Periodic Table ls atomic energy level — Hydrogen cation — Hydrogen atom 9 Hydrogen anion — Hydrogen molecule (18) Which best describes a typical step in the synthesis of a peptide (protein)? — H20 + HzN-CHR1-CO-NH-CHR2-C02H—>H2N-CHR,-COz-H + HzN-CHRz-CozH 0 HzN-CHRl-COZH + H2N~CHR2-C02H—>H2N-CHR1-CO-NH-CHR2-C02H + H20 — C + G —> C—G - Asp-Asp —> 2 Asp (19) The enzyme raises the activation energy barrier, slowing down the reaction Raising the temperature will slow down the reaction Adding the enzyme accelerates the reaction rate Adding the enzyme affects the energy difference between the starting material and produCt Catalysis by enzymes: ‘ Can occur on any part of the enzyme surface Occurs in a special region (cleft, groove), the active site Does not require direct participation in bond making/breaking by special group(s) on the enzyme Does not require special ionic, polar and/or hydrophobic interactions to bind E to S The figure below shows a pyruvate molecule binding to the active site of enzyme lactate dehydrogenase by: Like-like (Van der Waals) forces, H-bonding and ionic bonding Like-charge repulsion forces only H—bonding and ionic bonding only Weak forces, H—bonding and covalent (disulfide) bonds Comparing electronegativities, which is larger? C > F F > C H > O C > N Thermodynamics is concerned with kinetics with. .. The amount of heat produced in a reaction. . ..the rate of a reaction (one does not necessafily depend on the other) The amount of heat produced in a reaction. . ..the rate of a reaction (one depends on the other) The periodic table rows. . ..the periodic table columns None of the above Eating grass (vs. eating bread): The key nutritional problem for us (vs. cows, e.g.) is We lack an enzyme that cleaves the “up”C-O -C linkage between the glucoses in cellulose We lack an enzyme that cleaves the “down” C—O-C linkage between the glucoses in starch A single enzyme recognizes and cleaves both types of C-O-C linkage Cellulose is actually a protein The stomach has a pH ~2. This means that in the stomach; [H‘] is 2M [H‘] is 10'2M [H‘] is 10‘5M [H1 is 102M mwne point each. Max = 4, 0K to guess) Identify the following amino acids by name/abbreviation am by l-letter symbol: -—CH—-!:O|—0H ' H2N (LHZ ‘ E- %“2 /G l :4 13:0 fi 4’51 w—e A HzN—CH—C—OH I Ala, CH3 ...
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This note was uploaded on 07/22/2008 for the course CHEM 203Lxg taught by Professor Mc kenna during the Fall '07 term at USC.

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203f02_e2_key - Chemistry 203 Lg(Fall 02 Exam#2 La N...

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