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Recap of Adenylate Cyclase GPCR Signaling quiz

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  • What is the effector enzyme regulated by G proteins in adenylate cyclase GPCR signaling?
    Adenylate cyclase is the effector enzyme regulated by G proteins in this pathway.
  • Which hormone binds to the beta adrenergic GPCR to initiate the stimulatory pathway?
    Epinephrine (adrenaline) binds to the beta adrenergic GPCR to start the stimulatory pathway.
  • What happens to the G protein alpha subunit during activation in the stimulatory pathway?
    The alpha subunit exchanges GDP for GTP and dissociates to activate adenylate cyclase.
  • What is the substrate and product of adenylate cyclase?
    Adenylate cyclase converts ATP (substrate) into cAMP (product), a secondary messenger.
  • How does cAMP activate protein kinase A (PKA)?
    cAMP binds to the regulatory subunits of PKA, releasing the catalytically active subunits.
  • What is the cellular effect of PKA activation?
    PKA phosphorylates target enzymes, leading to various cellular responses.
  • How is the stimulatory signal terminated in adenylate cyclase GPCR signaling?
    Termination occurs via GTP hydrolysis by the alpha subunit, cAMP phosphodiesterase converting cAMP to AMP, and phosphatases removing phosphate groups.
  • What role does cAMP phosphodiesterase play in signal termination?
    cAMP phosphodiesterase converts cAMP into AMP, lowering cAMP levels and helping terminate the signal.
  • How does the inhibitory pathway affect adenylate cyclase activity?
    The inhibitory pathway suppresses adenylate cyclase activity, preventing ATP conversion to cAMP.
  • What is the function of the inhibitory G protein (Gi) in this pathway?
    Gi inhibits adenylate cyclase when its alpha subunit is activated by GTP binding.
  • What proteins are involved in GPCR desensitization?
    Beta adrenergic receptor kinase (BRC) and beta arrestin are involved in desensitizing the GPCR.
  • How does beta adrenergic receptor kinase contribute to desensitization?
    It phosphorylates the beta adrenergic GPCR, allowing beta arrestin to bind and inhibit signaling.
  • What effect does cholera toxin have on G protein signaling?
    Cholera toxin inhibits GTP hydrolysis in the stimulatory G protein, causing overactivation of adenylate cyclase and excessive cAMP production.
  • How does pertussis toxin affect the inhibitory G protein?
    Pertussis toxin prevents GDP-GTP exchange in Gi, inhibiting its activation and leading to increased adenylate cyclase activity.
  • Why are allosteric regulation and signal transduction important in cellular control?
    They allow cells to finely tune responses to external signals, ensuring proper regulation of cellular activities.