Second Messenger Hormones and Intracellular Signaling Quiz
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Questions and Answers

What is the primary method of hormone communication described in the text?

  • Activation of protein kinases
  • Interaction with extracellular receptors (correct)
  • Binding to intracellular receptors
  • Direct gene activation
  • How does an activated G protein affect adenylate cyclase?

  • It has no effect on adenylate cyclase
  • It inhibits adenylate cyclase activity
  • It degrades adenylate cyclase
  • It stimulates adenylate cyclase activity (correct)
  • Which molecule acts as the second messenger in the described signaling pathway?

  • G protein
  • Adenylate cyclase
  • Protein kinase
  • cAMP (correct)
  • What happens to a G protein after its GTP is hydrolyzed?

    <p>It becomes inactive</p> Signup and view all the answers

    What enzyme degrades cyclic AMP in the described pathway?

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

    Which type of G protein stimulates adenylate cyclase in the pathway?

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

    What enzyme is responsible for splitting the plasma membrane phospholipid PIP2 into DAG and IP3 in the PIP2-Calcium signaling mechanism?

    <p>Phospholipase C</p> Signup and view all the answers

    Which of the following is NOT considered a second messenger in hormone signaling?

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

    In the PIP2-Calcium signaling mechanism, what is the function of the liberated Ca2+ ions?

    <p>Bind to calmodulin to activate enzymes</p> Signup and view all the answers

    What is the term for the process where a hormone increases receptor number or affinity due to rising physiological levels?

    <p>Up-regulation</p> Signup and view all the answers

    Which phenomenon refers to the decreased receptor number or affinity due to prolonged exposure to high hormone concentrations?

    <p>Down-regulation</p> Signup and view all the answers

    In the context of hormone communication with target cells, what is the main function of G protein?

    <p>Activate adenylate cyclase</p> Signup and view all the answers

    What does cyclic AMP stand for in the context of second messenger method of hormone communication?

    <p>Cyclic Adenosine Monophosphate</p> Signup and view all the answers

    What is the name given to the U-shaped relationship wherein there are high risks at both extremes of exposure to substances like vitamin A?

    <p>Threshold effect</p> Signup and view all the answers

    How does the second messenger method of hormone communication proceed following activation of adenylate cyclase?

    <p>Increase in cyclic AMP levels</p> Signup and view all the answers

    Study Notes

    Hormone Signaling

    • Hormones bind to extracellular receptors, generating an intracellular molecule that mediates a response
    • Second messengers are molecules that transmit signals from hormones within the cell
    • There are different types of second messengers, including cyclic AMP (cAMP), cyclic GMP (cGMP), DAG, and IP3

    cAMP Signaling Pathway

    • When a hormone binds to its receptor, the receptor changes shape and activates a nearby inactive G protein
    • The G protein, now active, moves along the plasma membrane and binds to adenylate cyclase
    • Adenylate cyclase converts ATP to cyclic AMP (cAMP) with the help of a Gs protein
    • cAMP activates protein kinase, an enzyme that adds a phosphate group to various proteins, amplifying the signal
    • cAMP is degraded by the enzyme phosphodiesterase

    Calcium Signaling Mechanism

    • This pathway uses a G protein (Gq) and the enzyme phospholipase C
    • Phospholipase C splits PIP2 into DAG and IP3
    • DAG activates protein kinase, which triggers a response in the cell
    • IP3 releases Ca2+ from intracellular storage sites, which bind to calmodulin
    • The Ca2+-calmodulin complex activates enzymes that amplify the cellular response

    Insulin Signaling Pathway

    • Insulin binds to its receptor, activating its tyrosine kinase activity
    • The activated insulin receptor serves as a docking site for intracellular relay proteins
    • These proteins initiate a series of phosphorylations, triggering a cellular response

    Regulation of Hormone Receptors

    • Receptor numbers and affinity can change in response to hormone levels
    • Up-regulation: increased receptor number or affinity due to rising hormone levels
    • Down-regulation: decreased receptor number or affinity due to prolonged exposure to high hormone levels

    Dose-Response Curve

    • A graph showing the level of exposure (dose) and risk (increasing or decreasing) of an outcome
    • Can be applied to substances other than hormones
    • Threshold dose: the dose below which no effects are seen
    • U-shaped relationship: high risks at both extremes of exposure

    Hormone Communication Methods

    • Two primary methods: second messenger and direct gene activation
    • Second messenger method: hormone binds to receptor, activating a G protein, which generates a second messenger that triggers a response
    • Direct gene activation method: hormone binds to receptor, which activates genes directly, without a second messenger

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    Description

    Test your knowledge on how second messenger hormones bind to extracellular receptors and mediate intracellular responses through G proteins. Learn about the activation process of G proteins and the role of second messengers in cellular signaling.

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