Quiz 5

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Quiz 5
2010-10-07 14:28:02
biochemistry quiz

Quiz 5 for General Biochemistry
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  1. How many (i) transition states, and (ii) intermediates are associated with this mechanism:
    • (i) 5
    • (ii) 4
  2. Are the following statements correct descriptions of the steady state assumption used to derive the Michaelis-Menten equation?
    • The concentration of enzyme in an assay is much lower than the concentration of substrate.
    • The equilibrium between E, S, and ES is rapidly established.
    • The concentration of the ES complex does not change during the time frame where enzyme activity is being measured.
    • Product formed during the reaction does not react with E to reform ES at a significant rate
  3. Which of the following statements are true about the catalytic efficiency of an enzyme following the simple kinetic scheme shown here?
    • a low Km and high kcat increase catalytic efficiency.
    • the theoretic upper limit to catalytic efficiency is diffusion controlled.
    • catalytic efficiency is a second order rate constant with a value close to k1 for a “perfect” enzyme.
  4. The red line on the following reaction coordinate diagram is consistent with which kinetic mechanism?
  5. An enzyme that follows Michaelis-Menten kinetics has a Vmax of 200.0 units and a Km of 0.100 mM. What will be the activity for this enzyme when the substrate concentration is 0.500 mM?
    167 units
  6. Algebraically solve the Michaelis-Menten equation for [S] to answer the following question: what concentration of substrate gives an initial rate of 1500 units for an enzyme that exhibits a Vmax of 10,000 units and a Km of 0.25 mM?
    0.044 mM
  7. Kinetic analysis of a homodimeric enzyme of 150,000 molecular weight (that is the Mr of the dimer) catalyzing conversion of substrate S to product P provides the following kinetic constants: Vmax = 1000 units when 1 mg of enzyme is assayed. Assume each subunit contains an active site; i.e. there are two active sites per dimer. Calculate the turnover number for this enzyme. In units of s-1.
    1,250 s-1
  8. What forms of the enzyme do a competitive (C), noncompetitive (NC), and uncompetitive (UC) inhibitor bind to?
    • C:E only.
    • NC: E and ES.
    • UC: ES only.
  9. Using information from the following graph of 1/v vs. 1[S] for a particular enzyme, determine the values of Vmax and Km
    • Vmax = 50
    • Km = 0.4
  10. For the kinetic scheme shown below, which rate constants are first order?
    k2, k-2, k3, k-3 , k4 ,k-1
  11. Which statement(s) can be made with certainty about the following reaction:
    the reaction is exergonic
  12. The following graph shows a Lineweaver-Burke ( 1/v vs. 1/[S] ) plot (indicated by an arrow) for an enzymatic reaction transforming substrate S to product P. Which line could possibly represent a competitive inhibitor?
  13. Which of the following strategies for rate acceleration apply to ALL enzyme-catalyzed reactions?
    • binding energy
    • entropy trap
    • transition state stabilization
  14. In general, the structure of the active site of an enzyme will be most complementary to:
    the structure of the transition state(s)

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