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Allosteric Enzyme Conformations quiz

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  • What are the two conformations of allosteric enzymes called?
    The two conformations are the T (tense) state and the R (relaxed) state.
  • Which allosteric enzyme state is catalytically inactive and has low substrate affinity?
    The T (tense) state is catalytically inactive and binds substrate inefficiently.
  • What is the substrate affinity of the R state in allosteric enzymes?
    The R (relaxed) state has high substrate affinity and binds substrates efficiently.
  • How does the T state of an allosteric enzyme affect substrate binding?
    The T state binds substrates very inefficiently due to its tense conformation.
  • What is the allosteric constant (l naught) defined as?
    The allosteric constant l naught is the ratio of the concentration of T states to the concentration of free R states in the absence of substrate.
  • At low substrate concentrations, which state is favored in allosteric enzymes?
    The T state is thermodynamically favored at low substrate concentrations.
  • Does the allosteric constant l naught involve substrate-bound R states?
    No, l naught is the ratio of T states to free R states, not substrate-bound R states.
  • What type of kinetics do allosteric enzymes display on an enzyme kinetics plot?
    Allosteric enzymes display sigmoidal (S-shaped) kinetics on enzyme kinetics plots.
  • What does sigmoidal kinetics in allosteric enzymes suggest about substrate binding?
    Sigmoidal kinetics suggest positive cooperativity, where binding of one substrate facilitates binding of others.
  • How does substrate binding to the free R state affect the equilibrium between T and R states?
    Binding substrate to the free R state decreases its concentration, causing the equilibrium to shift towards producing more R state.
  • What is positive cooperativity in allosteric enzymes?
    Positive cooperativity is when binding of one substrate molecule makes it easier for additional substrate molecules to bind.
  • How does increasing the allosteric constant l naught affect the enzyme kinetics curve?
    A higher l naught makes the curve more sigmoidal, indicating greater cooperativity.
  • What happens to the enzyme kinetics curve when l naught is low?
    The curve becomes less sigmoidal and more closely resembles Michaelis-Menten kinetics.
  • Name the two models that explain sigmoidal kinetics in allosteric enzymes.
    The concerted (MWC) model and the sequential (KNF) model explain sigmoidal kinetics.
  • What role do allosteric effectors play in the concerted and sequential models?
    Allosteric effectors influence enzyme activity in both the concerted and sequential models.