Biochemistry quiz 5

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Biochemistry quiz 5
2013-11-05 14:01:46
biochemistry quiz

Biochemistry quiz five
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  1. The Km is...
    equal to the substrate concentration when the velocity is half its maximal value
  2. When substrate concentration is much greater than Km, the rate of catalysis approaches...
  3. List the five major classes of enzymes (in order)
    • oxidoreductase
    • transferase
    • hydrolase
    • lyase
    • ligase
  4. Be able to draw a Lineweaver-Burk plot. And label the x and y intercepts.
    Do it.
  5. Define what the slope equates to in a Lineweaver-Burk plot.
    slope = Km/Vmax
  6. In a biomolecular reaction, how would you carry out a kinetics experiment to determine Vmax for one of the reactants. Assume you desire pseudo-first order kinetics with respect to one of the reactants?
    For pseudo-first order kinetics in this situation you would use a substrate concentration for one of the reactants that is probably at least 100 fold higher than the Km where change in substrate concentration for that substrate would not affect Vmax.
  7. The slope of a Lineweaver-Burk plot for an enzyme is found to be 1.88. Its maximal velocity is 3.45 umoles/min. What is the Km?
    Km/Vmax=1.88; Vmas = 3.45 so Km/3.45 = 1.88Km = (3.45)(1.88) uM
  8. Formation of the ES complex results in an increase in entropy. [T/F]
    F; decrease
  9. What are the three main types of catalysis?
    Covalent catalysis;General acid-base catalysis;Metal ion catalysis
  10. In uncompetitive inhibition, the inhibitor can only bind to the ES complex to form an ESI complex. [T/F]
  11. Formation of the ES complex results in an increase in entropy. [T/F]
    F; decrease
  12. In near-attack complexes, reacting atoms and catalytic groups are precisey positioned for their roles in catalysis (proximity and orientation). [T/F]
  13. Transition state analogs (TSAs) are stable molecules that are...
    chemically similar to the transition state and structurally similar to the transition state
  14. Transition states are bound ______ than substrates.
    More tightly
  15. What is K-cat?
    substrate molecules converted to product per second
  16. Enzymes catalyze _____ favorable reactions.
  17. Enzymes provide cells with the ability to exert....
    kinetic control over thermodynamic potentiallity
  18. Living systems use enzymes to ____ and ____ of ______
    • accelerate;
    • control the rates;
    • vitally important biochemical reactions
  19. Nearly every _______ is catalyzed.
    biological reaction
  20. Enzymes are the ____ of ____.
    agents; metabolic function
  21. What common macromolecule is often burned or oxidized by enzymes?
  22. Enyzmes lower _____.
    delta G++
  23. The breakdown of glucose by ____ provides a prime example of a metabolic pathway.
  24. ________ is the ratio of the enzyme-catalyzed rate of a reaction to the uncatalyzed rate.
    catalytic power
  25. ____ is the term used to define the selectivity of enzymes for their substrates.
  26. _____ of enzyme activity ensure that the rate of metabolic reactions is appropriate to cellular requirements.
  27. Coenzymes and cofactors are....
    non-protein components essential to enzyme activity.
  28. _____ and ______ are non-protein components essential to enzyme activity.
    coenzymes and cofactors
  29. Cofactors are usually _____.
  30. Coenzyme usually refers to ____.
    organic non-protein molecules
  31. Enzymes selectively recognize proper ___  over other molecules.
    substrates (s)
  32. Enzymes produce ____ yields with ___ side products.
    very high; no
  33. Specificity is controlled by _____.
  34. _____ is controlled by structure.
  35. _____ and _____ of the substrate in the enzyme active site leads to catalysis.
    proximity and orientation
  36. Main classification: 1
    1: oxidoreductases
  37. Main classification: 2
    2: transferases
  38. Main classification: 3
    3: hydrolases
  39. Main classification: 4
    4: lyases
  40. Main classification: 5
    5: isomerases
  41. Main classification: 6
    6: ligases
  42. ____ is the branch of science concerned with the rates of reactions.
  43. _____ seeks to determine the maximum reaction velocity (Vmax) that enzymes can attain and binding affinities for substrates and inhibitors.
    enzyme kinetics
  44. What is the symbol for maximum reaction velocity?
  45. What is the abbreviation for the binding affinities for substrates?
  46. What is the abbreviation for the binding affinities for inhibitors?
  47. Analysis of enzyme rates yields insights into.....
    enzyme mechanisms and metabolic pathways
  48. What is the term for the amount of product formed (or substrate consumed) per unit time?
    rate or velocity
  49. What is the definition of the rate constant (k)?
    a proportionality constant that predicts the velocity at different concentrations of substrate
  50. What is a rate law?
    the actual mathematical relationship in a reaction
  51. What is that order of a reaction?
    the exponent in the rate equation
  52. What is the molecularity of a reaction?
    The number of molecules that must simultaneously interact
  53. What is the molecularity in: ?
    A----> P
  54. Kinetics can prove a reaction mechanism. [T/F]
  55. What is the half-time in a reaction?
    The time for one-half of the starting amount to disappear.
  56. A typical enzyme-catalyzed reaction must pass through a ____  ____.
    transition state
  57. The reaction rate is proportional to.....
    the concentration of reactant molecules with the transition-state energy
  58. The energy barrier of the transition state is known as ____.
    the free energy of activiation (delta G++)
  59. What is the abbreviation for the free energy of activation?
    delta G++
  60. Decreasing delta G++ _______ the reaction rate.
  61. Decreasing ______ increases the reaction rate.
    delta G++
  62. What is the difference between delta G and delta G++?
    • free energy change for a reaction is related to the equilibrium constant
    • the free energy of activation for a reaction is related to the rate constant
  63. Enzymes work by ___ the ____ by ____ with the ____, which promotes entry into the ____, ____ structure that promotes conversion to _____.
    • lowering;
    • free energy of activation;
    • combining;
    • reactants;
    • reactive, transition state;
    • product
  64. When S is low, the equation for rate is __ order in S
  65. When S is high, the equation for rate is __ order in S.
  66. When S is high, even if you add more substrate, the rate would ____.
    Thus v= ? at this point.
    not increase; v=Vmax
  67. The Michaelis-Menten equation describes a....
    rectangular hyperbolic dependence of v on S
  68. What is another name for Kcat?
    The turnover number
  69. What is Kcat?
    the number of substrate molecules converted to product per enzyme molecule per unit of time, when E is saturated with substrate
  70. What is the formula for catalytic efficiency?