Quiz 5 Key
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1-6. Use these terms: (C) kcat;   (E) [Et];   (H) kcat/KM ;   (K) KM ;    (S) [S];    (V) v0 ;    (X) Vmax .
Use each answer only once.

    C      the turnover number

    K      = [S] when v0 = 0.5 Vmax

    S       x axis for a Michaelis-Menton graph

    H      the specificity constant

    E       = [ES] in the steady state approximation

  V,X    has units of M s-1

7-9. Use these terms: (A) α; (B) α′; (C) competitive inhibitor; (M) mixed inhibitor;
(U) uncompetitive inhibitor. Use each answer only once .

  M,U    binds both E and ES

    C      resembles the substrate

    B       modifies [S] in the Michaelis-Menton equation for a mixed inhibitor

†10. Fill in the blank with the appropriate term:            KI             = [E] [I] / [E I].

1-6. Use these terms: (C) kcat;      (E) [Et];     (H) kcat/KM ;     (K) KM ;      (S) [S];      (V) v0 ;      (X) Vmax .
Use each answer only once.

    K      an overall rate constant

    X      the rate when the enzyme is saturated

    C      has units of s-1

    V      y axis for a Michaelis-Menton graph

    S       has units of M

    H      = 107 – 1010 for extremely efficient enzymes

7-9. Use these terms: (A) α ; (B) α′; (C) competitive inhibitor; (M) mixed inhibitor;
(U) uncompetitive inhibitor. Use each answer only once .

    B       = 1 + [I]/KI′

    C      binds E but not ES

  M, U   binds the enzyme, but not in the active site

†10. Fill in the blanks with the appropriate terms: KI′ =   [ES] [I]   /    [ESI]                   .

1-6. Use these terms: (C) kcat;   (E) [Et];   (H) kcat/KM ; (K) KM ;    (S) [S];    (V) v0 ;      (X) Vmax .
Use each answer only once.

    K      = [S] when v0 = 0.5 Vmax

    E       the denominator for kcat

    C      the turnover number

    V      the rate of the reaction in the first minute

    H      has units of M-1 s-1

  S, X    in the numerator of the Michaelis-Menton equation

7-9. Use these terms: (A) α; (B) α′; (C) competitive inhibitor; (M) mixed inhibitor;
(U) uncompetitive inhibitor. Use each answer only once .

    C      binds in the active site

    A      modifies KM in the Michaelis-Menton
              equation for a competitive inhibitor

    U      causes Vmax to decrease, which changes KM

10. Fill in the blank with the appropriate term(s): KI′ =      [ES] [I]           / [ESI].

1-6. Use these terms: (C) kcat;   (E) [Et];   (H) kcat/KM ;   (K) KM ;    (S) [S];    (V) v0 ;    (X) Vmax .
Use each answer only once.

    X      the numerator for kcat

    V      the rate of the reaction in the first minute

    C      has units of s-1

    K      often indicates an enzyme's affinity for substrate

    H      shows enzyme efficiency at
               low and high [S]

  K, S    in the denominator of the Michaelis-Menton
               equation

7-9. Use these terms: (A) α; (B) α′; (C) competitive inhibitor; (M) mixed inhibitor;
(U) uncompetitive inhibitor. Use each answer only once .

    A      = 1 + [I]/KI

    U      binds ES but not E

    C      causes KM to increase, but Vmax is unchanged

†10. Fill in the blanks with the appropriate terms: KI =        [E] [I]     /        [E I]      .

†Several people defined KI or KI′ in terms of α or α′. Although that can be done, I'd rather see you thinking about KI and KI′ as they relate to enzyme-inhibitor interactions.

Additional comment after grading: It may seem picky to be asking what the units are for these terms, but part of understanding what the terms represent is knowing what type of molecule or what type of interaction is involved. This type of question will be on quizzes all through the semester.

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