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Which type of signaling molecules can diffuse across the plasma membrane?

  • Charged molecules
  • Hydrophobic signaling molecules (correct)
  • Hydrophilic signaling molecules
  • Lipophilic signaling molecules

    • Hydrophilic signaling molecules bind to cytoplasmic receptors.

    False

    What does the activated receptor initiate in the signal transduction pathway?

    Intracellular signal transduction pathways

    The majority of signaling molecules cannot diffuse across the membrane and bind to specific ______ receptors.

    <p>cell-surface</p> Signup and view all the answers

    Match the following types of signaling molecules with their characteristics:

    <p>Steroids = Hydrophobic molecules that can diffuse across membranes Insulin = Hydrophilic molecule that binds to cell-surface receptors Catecholamines = Small hydrophilic charged molecules derived from amino acids Prostaglandins = Lipophilic molecules that bind to cell-surface receptors</p> Signup and view all the answers

    What is the result of terminating the cellular response?

    <p>Negative feedback from intracellular molecules</p> Signup and view all the answers

    Ubiquitination has no role in signaling regulation.

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

    What does the signal transduction pathway ultimately lead to?

    <p>Activation of effector proteins</p> Signup and view all the answers

    Which of the following best describes the function of MAP kinase?

    <p>Translocates into the nucleus and regulates gene expression</p> Signup and view all the answers

    Activated MAP kinase can phosphorylate p90RSK and promote its migration to the nucleus.

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

    Name one property enhanced by the phosphorylation of MAP kinase.

    <p>Catalytic activity</p> Signup and view all the answers

    The Notch receptor is activated upon binding to its ligand, _____, on an adjacent cell.

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

    Match the following components with their functions in MAP kinase signaling pathways:

    <p>MAP kinase = Translocates to the nucleus to regulate gene expression Raf = First kinase in the activation cascade MEK = Phosphorylates MAP kinases p90RSK = Phosphorylates SRF transcription factors</p> Signup and view all the answers

    What role do scaffold proteins play in MAP kinase pathways?

    <p>They isolate MAP kinase pathways to prevent cross-talk</p> Signup and view all the answers

    ADAM 10 is responsible for the activation of the Notch signaling pathway.

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

    The sequential phosphorylation in the MAP kinase pathway involves Ras, Raf, MEK, and _____

    <p>MAP kinase</p> Signup and view all the answers

    What initiates a typical signal transduction pathway?

    <p>A signal originating outside the cell</p> Signup and view all the answers

    Receptor-ligand interactions are nonspecific and can bind any signal molecule.

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

    Name one major class of receptors involved in signal transduction.

    <p>G-Protein coupled receptors</p> Signup and view all the answers

    The process of converting extracellular signals into _____ responses is known as signal transduction.

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

    Match the following terms with their respective descriptions:

    <p>G-Protein = Mediates signal transduction for GPCRs Second messenger = Small molecules that relay signals inside the cell Protein kinase = Enzyme that phosphorylates proteins Receptor tyrosine kinase = A protein that activates signaling pathways in response to growth factors</p> Signup and view all the answers

    Which of the following is an effect of signal transduction pathways?

    <p>Cellular metabolism changes</p> Signup and view all the answers

    Signal transduction pathways have no relevance to human diseases.

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

    What role do second messengers play in signal transduction?

    <p>They relay signals inside the cell.</p> Signup and view all the answers

    What is the primary function of a ligand when it binds to a receptor?

    <p>To change the properties of the receptor</p> Signup and view all the answers

    Receptors exhibit ligand-binding specificity and can bind to a wide variety of unrelated ligands.

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

    What does Kd represent in the context of receptor-ligand interactions?

    <p>The concentration of ligand at which half of the receptors are occupied</p> Signup and view all the answers

    ______ proteins act as molecular switches that are 'on' when bound to GTP.

    <p>GTPase switch</p> Signup and view all the answers

    Which of the following is NOT a feature of intracellular signal transduction?

    <p>Opening of ion channels</p> Signup and view all the answers

    What are second messengers and what role do they play in signaling?

    <p>Intracellular signaling molecules that carry signals from receptors and regulate activities of enzymes and nonenzymatic proteins.</p> Signup and view all the answers

    Match the following components with their functions:

    <p>GTPase switch proteins = Act as molecular switches Second messengers = Regulate enzyme activities Kinases = Add phosphate groups to proteins Phosphatases = Remove phosphate groups from proteins</p> Signup and view all the answers

    The effects of many hormones are mediated by first messengers alone, without the involvement of second messengers.

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

    What is the primary role of trimeric G proteins in the signaling pathway?

    <p>Transduce signals from cell-surface receptors to effector proteins</p> Signup and view all the answers

    G proteins remain in an active state when bound to GDP.

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

    Name a second messenger commonly involved in GPCR signaling pathways.

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

    The G protein-coupled receptors (GPCRs) are characterized by their _____ membrane-spanning domains.

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

    Match the following components with their roles in the G protein-coupled signaling pathway:

    <p>G protein = Transduces signals from GPCRs Adenylyl cyclase = Synthesizes cAMP cAMP = Acts as a second messenger GDP = Binds to inactive G protein</p> Signup and view all the answers

    Which subunit of the trimeric G protein primarily regulates the effector proteins?

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

    All types of GPCRs activate the same effector proteins.

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

    What happens to cAMP after its function as a second messenger?

    <p>It is hydrolyzed to AMP by cAMP phosphodiesterase.</p> Signup and view all the answers

    What effect does PKA have on glycogen synthase (GS)?

    <p>It inhibits GS.</p> Signup and view all the answers

    PKA is only involved in promoting glycogen degradation in liver cells.

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

    What does cAMP binding do to the catalytic subunits of PKA?

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

    PKA activates glycogen phosphorylase kinase (GPK) which subsequently activates __________.

    <p>glycogen phosphorylase (GP)</p> Signup and view all the answers

    Match the following components with their respective roles in glycogen metabolism:

    <p>Epinephrine = Stimulates PKA activation PKA = Inhibits glycogen synthesis glycogen phosphorylase = Degrades glycogen phosphoprotein phosphatase = Stimulates glycogen synthesis</p> Signup and view all the answers

    What initiates the cascade effect leading to glycogen breakdown in response to hormones?

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

    The activation of PKA is independent of cAMP levels.

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

    What ions are secreted during hormonal stimulation in liver cells, and what do they activate?

    <p>Ca2+ ions, glycogen phosphorylase kinase (GPK)</p> Signup and view all the answers

    Study Notes

    Cell Signaling - Signal Transduction

    • Signal transduction is the process of converting extracellular signals into cellular responses.
    • Extracellular signaling molecules regulate interactions between unicellular organisms and are critical for physiology and development in multicellular organisms.
    • Cells do not live in isolation.

    Signal Transduction Pathways

    • Depending on the signal, hydrophilic or hydrophobic communication steps occur:
      • Hydrophobic signals (steroids, thyroxine, retinoic acid) diffuse across the membrane and bind to cytoplasmic receptors. This receptor-signal complex moves to the nucleus to affect gene expression.
      • Hydrophilic signals (peptides, hormones, small charged molecules) bind to cell-surface receptors. This binding causes a conformational change, initiating intracellular signaling pathways. These pathways, often involving a cascade of protein interactions and second messengers, affect cellular metabolism, function, or movement.
    • Signaling molecules operate over various distances:
      • Endocrine signaling involves signal release into the bloodstream affecting distant cells.
      • Paracrine signaling involves signals affecting neighboring cells.
      • Autocrine signaling involves signals affecting the cell that produced them.
      • Juxtaposed signaling involves signals between membrane-attached proteins on adjacent cells.

    Receptor Proteins

    • Receptors are located on cell surfaces or intracellularly (cytosol/nucleus).
    • Ligands bind to specific receptors, changing their properties.
    • Ligand binding is specific, interacting with amino acids in the receptor.
    • Affinity of the receptor for a ligand is determined by Ligand concentration ([ligand]).
    • Cells modify or degrade ligands and receptors to terminate the response.

    Intracellular Signal Transduction

    • Includes second messengers and signal amplification.
    • Conserved intracellular proteins (GTPase switch proteins, kinases, phosphatases, adapter proteins).
    • Resetting or termination of signal is important.
    • Many hormones induce reactions by second messengers
    • Effects regulate multiple pathways.

    GTPase Switch Proteins

    • GTPase switch proteins are conserved GTP-binding proteins (molecular switches).
    • "On" state when bound to GTP; "off" state when bound to GDP.
    • Signal-induced conversion of inactive to active state is mediated by guanine nucleotide-exchange factor (GEF).
    • GTP hydrolysis (to GDP) is usually enhanced by a GTPase-accelerating protein (GAP).

    Protein Kinases

    • Proteins that add phosphate groups to other proteins, often affecting protein activity.
    • Phosphatases remove phosphate groups.

    Adapter Proteins

    • Coordinate the formation of multi-component signaling complexes.
    • Cluster membrane proteins.
    • Important for signal transduction.

    Regulation of Pathways

    • Cells appropriately respond by regulating signaling pathways.
    • Termination: Rapid termination of signaling (degradation of 2nd messengers, deactivation of proteins) occurs when ligands are removed.
    • Receptors often modify or degrade.

    G Protein-Coupled Signal Transduction Pathways

    • G proteins (trimeric) transduce signals from cell surface receptors to downstream effectors like enzymes forming cAMP etc. or cation channels.
    • Receptors have 7 membrane-spanning domains.

    Receptor Tyrosine Kinase (RTK) Pathways

    • RTKs bind to soluble or membrane-bound hormones (e.g., growth factors).
    • Binding activates receptor tyrosine kinase activity, activating downstream signaling cascades.
    • Signaling cascades lead to cell proliferation, differentiation and modulation of metabolism.

    Notch/Delta Signaling

    • Notch receptors bind to ligand Delta on adjacent cells.
    • Cleavage events activate transcription factor function in the nucleus.
    • Important in developmental processes (cell-fate determination).

    Signaling Controlled by Ubiquitination

    • Ubiquitination of target proteins is important for signaling pathways.
    • It's involved in many developmental processes like Wnt and Hedgehog pathways.

    NF-κB Pathway

    • Key regulator for cellular responses to infection and inflammation.
    • Degradation of inhibitor protein (I-κBα) activates NF-κB.
    • NF-κB translocates to the nucleus to regulate gene expression.

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    Cell Signaling - Signal Transduction Notes PDF

    Description

    This quiz explores the mechanisms of signal transduction, highlighting how extracellular signals are converted into cellular responses. It covers the roles of hydrophobic and hydrophilic signaling molecules, detailing their pathways and impact on gene expression and cellular functions.

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