PC 3: Intracellular Signaling and the Cell Membrane
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Questions and Answers

Which of the following is NOT a general model of intracellular signaling discussed in the text?

  • G-proteins
  • Desensitization and adaptation
  • Ionic and gaseous lipids (correct)
  • Signal amplification

    • What is the key function of receptors in the cell membrane?

  • Detecting intracellular signals
  • Accumulating 2nd messengers
  • Transforming extracellular signals into intracellular signals (correct)
  • Modifying cell function

    • Where do some 2nd messengers accumulate in the cell?

  • In the cytoplasm (correct)
  • In the nucleus
  • In the mitochondria
  • In the endoplasmic reticulum

    • Which of the following is NOT a function of the cell membrane in intracellular signaling?

    <p>Detecting extracellular signals</p> Signup and view all the answers

    What happens in an inactive intracellular signaling system?

    <p>No extracellular signal is present</p> Signup and view all the answers

    What happens in an active intracellular signaling system?

    <p>The 1st messenger becomes active</p> Signup and view all the answers

    According to the text, where can more detailed explorations of cell biology be found?

    <p>In the Molecular Biology of the Cell textbook</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of ATP to cAMP?

    <p>Adenylyl cyclase</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of cAMP to 5'-AMP?

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

    Which G-protein mechanism stimulates adenylyl cyclase and increases cAMP production?

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

    Which G-protein mechanism inhibits adenylyl cyclase and decreases cAMP production?

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

    What is the role of IP3 in the Gq GPCR signaling pathway?

    <p>It activates calcium release channel</p> Signup and view all the answers

    What is the function of calmodulin in the Gq GPCR signaling pathway?

    <p>It binds to calcium and activates effectors</p> Signup and view all the answers

    What is the unique feature of the Gq GPCR signaling pathway compared to other G-protein mechanisms?

    <p>It uses IP3 and DAG as second messenger systems</p> Signup and view all the answers

    Which of the following is true about G-protein coupled receptors (GPCRs)?

    <p>GPCRs have three protein subunits: alpha, beta, and gamma</p> Signup and view all the answers

    What happens when a ligand binds to a receptor associated with a Gs G-protein?

    <p>Gs releases GDP and binds GTP at the alpha subunit</p> Signup and view all the answers

    What is the role of adenylyl cyclase in GPCR signaling?

    <p>Adenylyl cyclase converts ATP to cAMP</p> Signup and view all the answers

    What happens when cAMP binds to protein kinase A (PKA)?

    <p>PKA binds to inhibitors, allowing the active parts of PKA to work</p> Signup and view all the answers

    What happens when the alpha subunit of a G-protein hydrolyzes GTP?

    <p>The alpha subunit becomes inactivated</p> Signup and view all the answers

    What is the role of the beta-gamma subunit in GPCR signaling?

    <p>The beta-gamma subunit detaches from the G-protein</p> Signup and view all the answers

    What is the main function of GPCRs in intracellular signaling?

    <p>To bind to and activate second messengers</p> Signup and view all the answers

    Which molecule can modulate the activity of many other effectors?

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

    What is the Nernst potential for K+?

    <p>-90 mV</p> Signup and view all the answers

    What is the effect of opening a channel that allows sodium to enter the cell?

    <p>The membrane becomes more inside-positive (depolarization)</p> Signup and view all the answers

    What is the effect of opening a channel that allows more potassium to leave the cell?

    <p>The membrane becomes more inside-negative (hyperpolarization)</p> Signup and view all the answers

    What is the effect of opening a channel that allows calcium to enter the cytosol?

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

    What is the cytosolic calcium concentration compared to the extracellular calcium concentration at rest?

    <p>Almost 10,000 times lower</p> Signup and view all the answers

    What is the role of Gi-α inactivating adenylyl cyclase?

    <p>Downregulating the activity of Gs</p> Signup and view all the answers

    What is the role of Gi-βγ?

    <p>Opening a K+ channel</p> Signup and view all the answers

    What is the role of the Na+/K+-ATPase and K+ channels in the cell membrane?

    <p>Maintaining an inside-negative membrane potential</p> Signup and view all the answers

    Which class of receptors has intrinsic enzyme activity?

    <p>Receptor Tyrosine Kinases (RTKs)</p> Signup and view all the answers

    What happens when a ligand binds to a receptor associated with a RTK?

    <p>The receptor dimerizes and activates a tyrosine kinase within the receptor</p> Signup and view all the answers

    What is the main function of RTKs in intracellular signaling?

    <p>To phosphorylate proteins</p> Signup and view all the answers

    Which signaling pathway involves the activation of phospholipase C?

    <p>Gq GPCR signaling pathway</p> Signup and view all the answers

    What is the role of Ras in the Ras cascade signaling pathway?

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

    Which ligand is NOT an example of a ligand that binds to RTKs?

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

    What happens when a ligand binds to a receptor monomer associated with an RTK?

    <p>The receptor dimerizes and each half phosphorylates the tyrosine residues on the other half</p> Signup and view all the answers

    Which G-protein mechanism inhibits adenylyl cyclase and decreases cAMP production?

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

    What is the role of the beta-gamma subunit in GPCR signaling?

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

    What is the effect of opening a channel that allows calcium to enter the cytosol?

    <p>Increase in cytosolic calcium concentration</p> Signup and view all the answers

    Which of the following is the key pathway for many growth factors?

    <p>Ras-Raf-MAP kinase pathway</p> Signup and view all the answers

    What is the role of PIP3 in the PI3K-Akt pathway?

    <p>It accumulates and forms lipid rafts in the membrane</p> Signup and view all the answers

    What is the function of Akt in the PI3K-Akt pathway?

    <p>It influences a range of intracellular targets</p> Signup and view all the answers

    Which molecule is produced from GTP by guanylyl cyclase in the nitric oxide-mediated pathway?

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

    What is the effect of elevated cytosolic cGMP in the nitric oxide-mediated pathway?

    <p>It activates a protein kinase (usually PKG)</p> Signup and view all the answers

    What is the role of nitric oxide synthase (NOs) in the nitric oxide-mediated pathway?

    <p>It produces nitric oxide from L-arginine</p> Signup and view all the answers

    Which of the following is NOT a characteristic of nitric oxide (NO)?

    <p>It has long-lasting effects</p> Signup and view all the answers

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

    <p>It inactivates itself by cleaving GTP to GDP</p> Signup and view all the answers

    What is the unique signaling mechanism of the PI3K-Akt pathway?

    <p>It is key to insulin signaling</p> Signup and view all the answers

    What is the role of PDK1 in the PI3K-Akt pathway?

    <p>It becomes activated by PIP3</p> Signup and view all the answers

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