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cAMP & PKA quiz

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  • What enzyme converts ATP into cAMP in the stimulatory GPCR pathway?
    Adenylyl cyclase converts ATP into cAMP when activated by the G protein.
  • What does cAMP stand for?
    cAMP stands for cyclic adenosine monophosphate.
  • How does cAMP activate Protein Kinase A (PKA)?
    cAMP acts as an allosteric activator by binding to PKA's regulatory subunits, causing the release of its catalytic subunits.
  • How many cAMP molecules are required to activate PKA?
    Four cAMP molecules are needed to bind to the regulatory subunits of PKA to activate it.
  • What is the structure of inactive PKA?
    Inactive PKA is a heterotetramer consisting of two regulatory and two catalytic subunits.
  • What type of residues does PKA phosphorylate on its target proteins?
    PKA phosphorylates serine and threonine residues on its target proteins.
  • What is the effect of phosphorylation by PKA on target proteins?
    Phosphorylation by PKA can either activate or inactivate target proteins, leading to various cellular responses.
  • What enzyme inactivates cAMP by converting it to AMP?
    cAMP phosphodiesterase converts cAMP into AMP, thereby inactivating the signal.
  • Does AMP activate PKA like cAMP does?
    No, AMP does not activate PKA; only cAMP can activate PKA.
  • What is the main difference between cAMP and AMP?
    The main difference is that cAMP has a cyclic phosphate group, while AMP does not.
  • What enzyme reverses the activity of PKA by removing phosphate groups?
    Serine/threonine phosphatases remove phosphate groups added by PKA, reversing its activity.
  • What is the role of serine/threonine phosphatases in the signaling pathway?
    They help reset the pathway by dephosphorylating proteins phosphorylated by PKA.
  • What triggers the activation of the G protein in the GPCR pathway?
    Binding of a ligand such as epinephrine to the GPCR triggers G protein activation.
  • What happens to the G protein after GPCR activation?
    The G protein exchanges GDP for GTP, and its alpha subunit dissociates to activate adenylyl cyclase.
  • How is the GPCR signaling pathway terminated?
    Termination occurs by inactivation of cAMP via phosphodiesterase, inactivation of PKA via phosphatases, and GTPase activity of the G protein alpha subunit.