Cell Biology: Receptor Activation
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Questions and Answers

Which type of receptor does not use a secondary messenger?

  • α1-adrenergic receptor
  • Phospholipase C
  • Receptor tyrosine kinase (RTK) (correct)
  • G-protein coupled receptor (GPCR)

    • What is the function of Grb2 and Sos adaptor proteins?

  • To activate the Ras-MAP kinase pathway
  • To inhibit the EGF signalling pathway
  • To phosphorylate tyrosine residues
  • To bind to the receptor tyrosine kinase (correct)

    • What is the consequence of adrenaline binding to the α1-adrenergic receptor?

  • Autophosphorylation of tyrosine residues
  • Inhibition of the EGF signalling pathway (correct)
  • Activation of phospholipase C
  • Activation of the Ras-MAP kinase pathway

    • What is the role of Ras in the EGF signalling pathway?

    <p>To trigger a kinase cascade</p> Signup and view all the answers

    What is an example of convergence in cell signalling?

    <p>Different signals triggering the same pathway</p> Signup and view all the answers

    What is the role of MAPKK in the Ras-MAP kinase pathway?

    <p>To activate MAPK</p> Signup and view all the answers

    What is the function of PKA in the adrenaline signalling pathway?

    <p>To inhibit the EGF signalling pathway</p> Signup and view all the answers

    What is the consequence of EGF binding to the EGF receptor?

    <p>Autophosphorylation of tyrosine residues</p> Signup and view all the answers

    What is the primary function of transmembrane receptors in signal transduction pathways?

    <p>To transmit signals from the extracellular environment to the nucleus</p> Signup and view all the answers

    Which of the following is NOT an example of a second messenger?

    <p>Glucagon</p> Signup and view all the answers

    What is the primary role of G proteins in signal transduction pathways?

    <p>To activate downstream kinases and trigger signalling cascades</p> Signup and view all the answers

    Which of the following is an example of a metabolic process regulated via intracellular signalling?

    <p>Glucagon-stimulated glycogen breakdown</p> Signup and view all the answers

    What is the primary role of phospholipase C in signal transduction pathways?

    <p>To hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) to generate IP3 and diacylglycerol</p> Signup and view all the answers

    Which of the following is an example of a cellular response to an extracellular signal?

    <p>Histamine release from mast cells</p> Signup and view all the answers

    What is the primary function of receptor tyrosine kinases (RTKs) in signal transduction pathways?

    <p>To phosphorylate and activate downstream targets</p> Signup and view all the answers

    Which of the following is an example of an extracellular signal?

    <p>Glutamate</p> Signup and view all the answers

    What is the result of the binding of a signal molecule to a β-adrenergic receptor?

    <p>The receptor undergoes a conformational change, allowing G-protein binding.</p> Signup and view all the answers

    What is the function of the α subunit in the G-protein complex?

    <p>To bind to the effector enzyme and activate it.</p> Signup and view all the answers

    What is the result of GTP hydrolysis to GDP in the G-protein complex?

    <p>The α subunit is inactivated and the complex re-associates.</p> Signup and view all the answers

    What is the role of the G-protein in the β-adrenergic receptor signalling pathway?

    <p>To translate the signal from the receptor to the effector enzyme.</p> Signup and view all the answers

    What is the result of the dissociation of the G-protein complex?

    <p>The α subunit is activated and free to bind to the effector enzyme.</p> Signup and view all the answers

    What is the role of GDP in the G-protein complex?

    <p>To inactivate the G-protein complex.</p> Signup and view all the answers

    Which of the following hormone types binds to a receptor in the cytosol and triggers a response inside the cell?

    <p>Steroid</p> Signup and view all the answers

    What is the result of the binding of acetylcholine to nicotinic acetylcholine receptor?

    <p>Depolarisation of membrane due to flow of ions</p> Signup and view all the answers

    What is the function of the DNA binding domain in steroid hormones?

    <p>To bind to specific DNA sequences</p> Signup and view all the answers

    What is the consequence of the binding of steroid hormone to its receptor?

    <p>Conformational change that allows DNA binding</p> Signup and view all the answers

    What is the role of G-protein-coupled receptors (GPCRs) in cell signalling?

    <p>To generate secondary messengers</p> Signup and view all the answers

    What is the consequence of the activation of adenylyl cyclase by G-protein-coupled receptors (GPCRs)?

    <p>Generation of cAMP</p> Signup and view all the answers

    What is the function of the hormone binding domain in steroid hormones?

    <p>To bind to the hormone</p> Signup and view all the answers

    What is the consequence of the activation of phospholipase C by G-protein-coupled receptors (GPCRs)?

    <p>Generation of IP3 and DAG</p> Signup and view all the answers

    What is the consequence of GTP hydrolysis in the G-protein coupled receptor signalling pathway?

    <p>Re-association of the G-protein complex and termination of signalling</p> Signup and view all the answers

    What is the role of the regulatory subunit in the cAMP dependent protein kinase A (PKA) pathway?

    <p>Binding to cAMP</p> Signup and view all the answers

    What is the consequence of phosphorylase kinase activation in the glycogen breakdown pathway?

    <p>Activation of glycogen phosphorylase</p> Signup and view all the answers

    What is the role of phosphodiesterase in the cAMP signalling pathway?

    <p>Converting cAMP to AMP</p> Signup and view all the answers

    What is the consequence of CREB phosphorylation in the cAMP signalling pathway?

    <p>Stimulation of gene transcription</p> Signup and view all the answers

    What is the role of Gαq in the GPCR signalling pathway?

    <p>Activating phospholipase C</p> Signup and view all the answers

    What is the role of IP3 in the GPCR signalling pathway?

    <p>Activating Ca2+ channels</p> Signup and view all the answers

    What is the consequence of DAG and Ca2+ activation in the GPCR signalling pathway?

    <p>Activation of protein kinase C</p> Signup and view all the answers

    What is the role of cAMP in the signal amplification pathway?

    <p>Activating PKA</p> Signup and view all the answers

    What is the consequence of PKA activation in the signal amplification pathway?

    <p>Activation of phosphorylase kinase</p> Signup and view all the answers

    Study Notes

    Receptor Activation of Phospholipase C

    • α1-adrenergic (adrenaline) receptor directly activates enzymatic kinase cascade without secondary messenger
    • Binding of EGF triggers autophosphorylation of tyrosine residues in cytoplasmic domain of receptor (Receptor Tyrosine Kinase, RTK)
    • Adaptor proteins containing phosphotyrosine binding domains (SH2 and PTB) bind to receptor
    • Complex of Grb2, Sos, and receptor activates Ras, a monomeric G-protein
    • Ras triggers a kinase cascade (Ras-MAP kinase pathway) that activates transcription factor

    G-Protein Coupled Receptors (GPCR)

    • Generate cAMP, leading to activation of PKA
    • Generate IP3, DAG, and Ca2+, leading to activation of PKC
    • α-subunit of G-protein interacts with effector enzymes
    • G-proteins can trigger different pathways, causing convergence and cross-talk

    Intracellular Signalling

    • Cells respond to extracellular signals through G-protein coupled receptors (GPCR) and receptor tyrosine kinase (RTK)
    • GPCR can trigger different pathways, leading to convergence and cross-talk
    • Different signals can trigger different pathways, causing overlap and cross-talk

    Teaching Objectives

    • Describe different ways for cells to signal to each other
    • Explain the term 'second messenger' and give examples
    • Describe the importance of transmembrane receptors and their associated signalling pathways in controlling gene activity
    • Give examples of the roles of G proteins, cAMP, phospholipase C, diacylglycerol, inositol triphosphate (IP3), and Receptor Tyrosine Kinase (RTK) in signal transduction pathways
    • Outline a metabolic regulated via intracellular signalling
    • Recognise that overlap of signalling pathways can occur
    • Beware that intracellular signalling is important in the action of drugs

    Cellular Responses

    • Change metabolic activities
    • Secrete and release molecules
    • Changes in gene expression
    • Sensory perception

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    Description

    This quiz covers the activation of phospholipase C and receptor tyrosine kinase, including the binding of EGF and autophosphorylation of tyrosine residues.

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