Quiz 11 Key
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1-3. Answer with one of the these liver cell enzymes: (H) hexokinase I; (X) hexokinase IV;
(F) FBPase–1; (G) glucose–6–phosphatase; (K) PFK–1; (R) pyruvate kinase.

    H      an isozyme with a low KM

    F     inhibited by fructose-2,6-bis-phosphate

    X     an isozyme with a high KM

    K    activated by fructose-2,6-bis-phosphate

    K, R    inhibited by ATP

    G    located in the endoplasmic reticulum
                   (ER)

    K, R    activated by AMP

    X    inhibited when bound by a regulatory
                   protein

    G, H    not regulated

    R    inhibited when phosphorylated by PKA

  R      activated by fructose-1,6-bis-phosphate

4-5. Write ↑ or ↓ in the blank. "Eventually" means as a result of more than one step.

Activating PKA causes PFK–2 activity to      ↓       so that, eventually, gluconeogenesis         ↑       .

Activating PKA causes FBPase–2 activity to      ↑         so that, eventually, gluconeogenesis       ↑     .

Activating PKA causes [fructose–2,6–bis-P] to    ↓           so that, eventually, glycolysis     ↓          .

Inhibiting PKA causes PFK–2 activity to        ↑      so that, eventually, gluconeogenesis         ↓      .

6-10. Use the enzymes involved in glycogen metabolism: (D) debranching enzyme;
(B) branching enzyme; (G) glycogenin; (M) phosphoglucomutase;
(P) glycogen phosphorylase; (S) glycogen synthase; (U) UDP–glucose pyrophosphorylase
Do not use a choice more than once. Answer with only one choice.

    M     glucose–6–P ↔ glucose–1–P

    M      Glucose–1,6–bis-P is an
               intermediate in the reaction.

   S, D     Makes an α–(1→4) bond

    D     Hydrolyzes an α–(1→6) bond

    B    Makes an α–(1→6) bond

    P     Adds Pi to break an α–(1→4) bond

    U     Requires UTP as a substrate

    S     Requires UDP–glucose as a
               substrate

   P      Requires Pi as a substrate

   S      Converts glycogenn to
               glucogen(n+1)

   G      Synthesizes a glycogen primer

   P     Converts glycogen(n+1) to
               glycogenn

    U     Produces UDP–glucose + PPi

   U,S,B.G     Only required for glycogen
                 synthesis

    P, M     Produces glucose–1–P

    P, D     Only required for glycogen
                  degradation

Comments after grading: The branching enzyme only makes an α–(1→6) bond. The debranching enzyme, when it transfers a short chain, does make an α–(1→4) bond as well as breaking an α–(1→6) bond.

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