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Practice - Biosignaling quiz

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  • What does the dissociation constant (Kd) represent in receptor-ligand interactions?
    Kd measures the binding affinity between a receptor and its ligand; a lower Kd indicates higher affinity.
  • How is Kd similar to Km in enzyme kinetics?
    Kd is analogous to Km because both describe the affinity of a molecule for its binding partner—Kd for receptors and Km for enzymes.
  • What happens to GDP in the alpha subunit of a G protein when a ligand binds to a G protein-coupled receptor?
    GDP is replaced by GTP, activating the G protein.
  • What is the role of GTPase activity in G proteins?
    GTPase activity allows the G protein to hydrolyze GTP back to GDP, inactivating itself.
  • How is protein kinase A (PKA) activated?
    PKA is allosterically activated when cyclic AMP (cAMP) binds to its regulatory subunit, causing the catalytic subunit to be released.
  • What is the effect of cAMP binding on the regulatory subunit of protein kinase A?
    cAMP binding causes the regulatory subunit to dissociate from the catalytic subunit, activating PKA.
  • What are the products of phospholipase C hydrolyzing PIP2?
    Phospholipase C hydrolyzes PIP2 into diacylglycerol (DAG) and inositol triphosphate (IP3).
  • What is the function of IP3 in cell signaling?
    IP3 triggers the release of calcium from intracellular stores.
  • How is protein kinase C activated?
    Protein kinase C is activated by diacylglycerol (DAG) and calcium ions.
  • What triggers autophosphorylation in receptor tyrosine kinases?
    Ligand-induced dimerization and ATP binding trigger autophosphorylation in receptor tyrosine kinases.
  • What is the role of ATP in receptor tyrosine kinase activation?
    ATP provides the phosphate groups for autophosphorylation of the receptor.
  • How does insulin signaling affect glycogen synthase?
    Insulin signaling activates protein kinase B, which inactivates GSK3, leading to activation of glycogen synthase.
  • What effect does insulin have on GLUT4 transporters?
    Insulin signaling causes GLUT4 transporters to move to the plasma membrane, increasing glucose uptake.
  • Why do steroid hormones require carrier proteins in the blood?
    Steroid hormones are hydrophobic and cannot dissolve in the aqueous environment of blood, so they need carrier proteins for transport.
  • Can steroid hormones diffuse freely across cell membranes? Why or why not?
    Yes, steroid hormones can diffuse freely across cell membranes because they are hydrophobic.