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203f00_e2_key - Chemistry 203 Lg (Fall 00) Quiz #2 Last...

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Unformatted text preview: Chemistry 203 Lg (Fall 00) Quiz #2 Last Name: October 24, 2000; 11:00-11:50 am. First Name: Prof. Charles E. McKenna Social Security lg T.A:‘ , I: K, ./ p. INITIAL OF LAST NAME Please do not open this exam until you are told to do so. Write leginy to avoid confusion. GOOD LUCK ! ! -- Question # Points Score ' n“ I" l y‘ ,a i r I will observe the rules of Academic n - » taking this exam. Student Signature Macintosh HD:Desktop Folder:0203F/OOEX#2 Circle the most nearly correct answer. (4 Pts.) (1) Applying the Octet Rule for bonding, a correct structure is: T —— H—T—KHH H we T 4,: _ /H u H W ‘\ H H T _: /H __..__. H H H H l .. H — “'T‘K/‘H (2) The formal charges in the molecule to the right are: 2502 0 C— 0+ - C zero 0 zero - C+ 0+ (3) (4) (5) The number of electrons on a carbon atom (C) available for bonding (valence electrons) contains: both an ether and an amine group both a ketone and an ester group both an amide and an acid group both an alkene and an alcohol group In a bond-breaking process like H—H -- >2 H. the product (2H atoms) is more stable than the starting material (Hz) the reaction happens more slowly at higher temperatures energy is released energy must be supplied A molecule: if 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 are true (7) pH: - measures the concentration of water in water - measures the acidity of a given compound - is typically 10-11 for gastric juices and 3-4 for blood D is close to neutral for blood, but and 1—2 for gastric juices (8) Which one of the following amino acids is NOT chiral? M H2 fl /\ > c—OH (9) How many different tripeptides HzN-aal-aaz- aaz-COZH are possible, assuming aan could be any of the common amino acids? - 400 6 8000 (10) A-A reacts with 8-8 to make 2 molecules of AB. Bond energies: A-A 50, B—B 40; AB 100 all in kJ/mole. The net change in energy for this reaction is (remember, minus means energy is released): - + 10 - - 10 d - +110 (11) Primary vs. tertiary structure of a protein: - primary = repeating coils or sheets, tertiary = random structure C3 primary = amino acid sequence, tertiary = overall conformation or shape in 3D - primary = amino acid sequence, tertiary repeating coil or sheet ‘ - primary = overall conformation in 3D, tertiary = grouping of > 2 protein molecules (12) To make a 0.1 M (molar) solution of HCl in H20 : - dissolve 1 molecule of HCl in 1000 g of water 9 add 3.65 g of HCl in up to 1 liter of water - dissolve 36.5 g of HCl in up to 1 liter of water - add 36.5 of HCl to 18 g of water (13) The compound Li” Cl' has: - covalent bond only - hydrogen bond only 0 ionic bond only - both covalent and ionic bonds (14) Which among the following has the most polar covalent bond @ F—CH3 - H3C—CH3 - MEN ' (15) In the reaction H2+ HZC = CH2 + Pd/C --> H3C—CH3 + Pd/C the total number of old bonds broken when the reactants bind to the surface of the catalyst is: I OOJ>UJN (16) Myoglobin, the O2 — storage protein of muscle (shown below): as several extensive a—helical regions has several extensive “beta sheet” regions does not require the help of an Fe atom tobind the 02 has an amino group terminating each end (17) An amino acid has equilibria in water: + + _ ‘ HsN—CHR—COZH __ H3N_CHR—C02 +H+ (1)pKa=4 + _ H 3N_CHR—CC)2 HgN—CHR—00; +H+ (2) pKa: 10 At pH = 12, the most likely total charge of the amino acid is: - +1 @3 -2 (18) The strongest secondary type of bond found in proteins is - Van der Waals (like-like) bond - Hydrogen bond Ionic bond 0 Covalent s-s bond (19) The picture below represents: / electron —‘7 = First Row, Periodic Table x atomic energy level Hydrogen cation @ Hydrogen atom Hydrogen anion - Hydrogen molecule (21) _— — f: (22) Comparing structural vs. globular proteins: structural proteins: are water—soluble have diverse secondary structures are typically catalysts are found in human hair, wool and silk The least polar molecule is: CH3OH H20 CH3-O-CH3 0 Which best describes a typical step in the Mm of a peptide (protein)? HZN-CHRl-COZH + HZN-CHRz-COZH ——> HzN-CHRl-CO-NH-CHRz-COZH + H20 HZN -CHR1—COZH + HzN-CHRz-COZH —> HZOC-CHR,-NH-CO—CHR2-NH2 + H20 A + T —> A-T HZN—CHRl-CO-NH-CHRz-COZH + H20 —> HZN-CHRrCOZH + HZN-CHRz-COZH Protein folding in water solutions: places polar and charged groups in the interior of the protein places non-polar groups in the interior of the protein places both types of groups in the interior of the protein determines the primary structure of the protein (24) ,3 Energy Transition State Product The reaction diagram above shows the change in energy when the substrate S (starting material) is converted to the product P, without (A) and with (B) enzyme E. According to the diagram: the enzyme lowers the activation energy barrier, speeding up the reaction temperature will slow down the reaction adding the enzyme has no effect on the reaction rate the bigger the difference in energy between starting material and product, the slower the reaction Catalysis by enzymes: occurs in a special region (cleft, groove), the active site can occur on any part of the enyzme surface does not require special ionic, polar and/or hydrophobic interactions to bind E to S never requires direct participation in bond making/breaking by special group(s) on the enzyme Simplified Periodic Table Representative element: (nonmetals) s a 9 to a o 5 Ne IO.“ [5.9996 [8.9984 20.179 l ' l3 :4 i I“! Is ' C1 Ar 35.453 393‘! DOUBLE BONUS QUESTION! (plus 2 points each!) Identify the following amino acids by name/abbreviation gm: byl-letter symbol: ll HgN—TH—C—OH 94 47 C 10 ...
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203f00_e2_key - Chemistry 203 Lg (Fall 00) Quiz #2 Last...

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