203f05_e2_key

203f05_e2_key - Chemistry 203 Lg (Fall 2005) Exam #2 Last...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chemistry 203 Lg (Fall 2005) Exam #2 Last Name: October 1 1, 2005; 1 1:00-12:00 First Name: Professor Amy M. Barrios Student ID # Professor Charles E. McKenna T.A: INITIAL OF KAME Please do not open this exam until you are told to do so. Write legibly to avoid confusion. GOOD LUCK ! ! Circle the most nearly correct answer. (4 Pts.) (1) Difference between drugs acting competitively vs. non-competitively to inhibit an enzyme: — competitive drug always binds at a site remote from the active site — competitive drug always causes irreversible inactivation of the enzyme — non—competitive drug never binds to the active site of an enzyme — non-competitive drug can bind either at the active site or at a site remote from the active site (2) The alpha helix and beta-sheet substructures found in most proteins are largely due to: — Internal H—bondin from one amino acid to another in the same protein — external H-bonding to H20 — Van der waals (like-like) forces — Ionic charge attraction/repulsion forces (3) Which best describes a typical step in the synthesis of a peptide (protein)? — H20 + H N—CHR -CO-NH—CHR —CO H——>H N-CHR —CO —H + HZN—CHRz-COZH HR -CO H + H20 — C+G—>C—G — Measures the concentration of water in water — Measures the acidity of a given compound ls typicall -11 for Is close to neutral for blood but and 1-2 for astric 'uices astric 'uices and 3-4 for blood (5) Catalysis by enzymes: — Can occur on an art of the enz me surface — Never requires direct participation in bond making/breaking by special group(s) on the enzyme — Does not require ionic, polar or hydrophobic interactions to bind E to S (6) An amino acid has the following equilibria in water: + ._ HgN—CHR—002 + H+ (l) pKa = 4 + Haw—CHn—COZH + _ _. H3N—CHR~COZ -———- HzN—CHR’COQ +H” (2) pKa=10 At pH = 12, the most likely total charge of the amino acid is: (7) How many valence electrons do C and S have: — 8and16 — 6and 16 — 4and8 (8) Which statement is true? — A reaction with a positive k} is favorable — A reaction with a positive x is unfavorable # A reaction with a positive 3-! requires energy — A reaction with a negative EH and a positive NS will be unfavorable (9) The molecular shape of a carbon with 4 things bound to it (for example, CH4) can best be described as: — Rectangular — Square planar — Trigonal — Tetrahedral (10) A problem in creating an “AIDS vaccine” is: - attenuated virus in vaccine may revert and cause the disease — vaccinated people are likely to test “HIV—positive” — vaccine may not give long-term immunity due to virus mutation — all of the above (11) Which NEUTRAL compound is NOT stable according to valence rules: — Bel—l2 — NH3 — H20 (12) The most effective method for transmitting HIV from an infected person to an uninfected person is: ( — blood transfusion ) - needle stick - sexual contact - coughing or sneezing — A benzene ring and an ether — An amide and an ester 0 Mk (13) The drug Practolol (on the right) contains: />(\H : H OH — A chiral carbon and a tertiary amine HN — All of the above \H/ o (14) The figure below shows a pyruvate molecule binding to the active site of enzyme lactate dehydrogenase by: - Like—charge repulsion forces only — H-bonding and ionic bonding only — Weak forces, H-bonding and covalent (disulfide) bonds (15) In the following molecule, what is the OPTIMAL H—C—H bond angle? — 90° (I? ' 109'. H-—C——H — 180° (16) Which ion is the most stable according to valence rules? — He+ — Ne+ — P (17) Which of the following molecules is a component 0 I A but NOT RNA? W NH2 0:9-0—3 t > OH N/ N .1th m CH phosphate _ backbone adenine rlbose (18) Which of the following shows the correct number of valence electrons for the NEUTRAL ELEMENT indicated? ' 2P' 2F: (19) Koch’s postulates are one way to tell if a virus or bacteria causes a given disease. Which of the following is NOT true of HIV/AIDS? - HIV is found in all cases of AIDS - HIV can be isolated from patients with AIDS and grown in pure culture - HIV will reproduce AIDS when introduced into a susceptible host (20) Arrange the following atoms in order from LEAST ELECT RONEGATIVE to MOST ELECT RONEGATIVE: Al, F, Na, N — F<N<Al<Na — F<A1<N<Na — Na<N<Al<F (— Na<Al<N<Ffi) (21) Which of the following is NOT a true statement about the immune system? - phagocytes “eat” bacteria and viruses roduce antibodi .. - ' - “ ” of revious infections - T4 cells produce antigens to combat the antibodies produced by invaders - T8 cells recognize and kill foreign invaders (22) What is the predominant secondary structure in the following protein: —— Alpha helix — Disulfide bonds — Beta sheet — Van der Waals interactions (23) Which of the following bonds shown is the most polar covalent bond: — CH3—CH3 — HzN—Clj3 — NNN (24) Which amino acid does NOT have a chiral center? i H2N—(I3H— C—OH CH3 0 O H II C—OH H2N——CH-C-—OH H I (le—CH3 HN CH3 amber +ha+ +ho [Marathon all ma lines in m chum'tnl armature, mama/d? A __0_ . gadn 0 Mat”? have 4- lamdl‘ +’ ‘90 Ch‘vill So wry I" m H 6 WW 1': rwlful in Mr (nurture. Energy Transition State (25) The reaction diagrams above show the change in energy when the starting material is converted to the product (A) without an enzyme catalyst and (B) with an enzyme catalyst. According to the diagrams: — the enzyme raises the activation energy barrier, slowing down the reaction — lowering the temperature will slow down the reaction — adding the enzyme lowers the ener of the transition state — adding the enzyme affects the energy difference (m) between the starting material and the product BONUS QUESTION (4 points max): a) If two nitrogen atoms come together to form a molecule, how many electrons from each atom must be shared in order to give the most stable molecule possible? (2 pts) :N. ~10: .__., :NEN: N dahm‘zd‘ ' ' 3 alwth b) Since the year 2000, have the number of AIDS cases reported in the US each year increased, decreased, or remained about the same? Why do you think this is? (2 pts)? it 04'— Albs am: has remained oiloan- +ho cam, __\___‘ We are wry possible wich {w +m 8:25 5:3 mahocamoca coo___w E32836 EemmcmmE E368 _m _< 92 m2 : 888 E25: 3 m SEE: :mmofi? m: I r ABEEEE 2an 2.828 9: ...
View Full Document

Page1 / 9

203f05_e2_key - Chemistry 203 Lg (Fall 2005) Exam #2 Last...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online