Cell Signaling and Signal Transduction Quiz
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Questions and Answers

What is the primary function of a receptor protein?

  • To recognize and bind specific signal molecules (correct)
  • To facilitate energy production in cells
  • To transport molecules across the cell membrane
  • To store genetic information

    • What type of signaling molecule is present outside the cell and triggers a response upon binding?

  • Extracellular signaling molecule (correct)
  • Intracellular signaling molecule
  • Endocrine signaling molecule
  • Paracrine signaling molecule

    • How can different cells respond differently to the same signal molecule?

  • Cells have identical receptors
  • Cell responses are always identical regardless of receptor type
  • All cells have the same internal signaling pathways
  • Different receptor types are expressed in different cells (correct)

    • What do intracellular signaling molecules do in the context of signal transduction?

    <p>They convey and amplify signals inside the cell</p> Signup and view all the answers

    What is the importance of cell signaling for both unicellular and multicellular organisms?

    <p>It allows for coordination of behavior and physiological functions</p> Signup and view all the answers

    What is molecular on/off switching in signal transduction?

    <p>It is the mechanism of turning signaling pathways on or off</p> Signup and view all the answers

    Which type of signaling involves molecules that act on nearby cells?

    <p>Paracrine signaling</p> Signup and view all the answers

    Which of the following statements about cell signaling is incorrect?

    <p>All cells respond to signals in the same way</p> Signup and view all the answers

    What initiates the receptor's function in cell signaling?

    <p>A signaling molecule</p> Signup and view all the answers

    What is the primary role of relay molecules in signal transduction?

    <p>To convert extracellular signals into intracellular responses</p> Signup and view all the answers

    Which process describes the conversion of information from one form to another within the cell?

    <p>Signal transduction</p> Signup and view all the answers

    Which of the following is NOT an outcome of a cellular response during signal transduction?

    <p>Relay signal initiation</p> Signup and view all the answers

    During which stage of cell signaling does the extracellular signal get converted to an intracellular signal?

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

    What characterizes steroid hormones in terms of their signaling mechanism?

    <p>They signal through intracellular receptors.</p> Signup and view all the answers

    Which statement about nitric oxide (NO) is correct?

    <p>It directly activates intracellular enzymes.</p> Signup and view all the answers

    How do G proteins function as molecular switches in signal transduction?

    <p>They get activated by phosphorylation.</p> Signup and view all the answers

    Which of the following is true about the responses of cells to the same signaling molecule?

    <p>Differing receptors in different cells can lead to varied responses.</p> Signup and view all the answers

    What role do kinases play in signal transduction?

    <p>They activate signaling proteins through phosphorylation.</p> Signup and view all the answers

    What primarily determines the variation in cellular response to the same signal molecule?

    <p>The receptor types present on the cell</p> Signup and view all the answers

    Which type of signal molecule relies on cell-surface receptors due to its chemical nature?

    <p>Growth factors</p> Signup and view all the answers

    What is the primary mechanism by which hydrophobic signal molecules exert their effects?

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

    Which principle is NOT associated with the general process of signal transduction?

    <p>Universal response to all signal molecules</p> Signup and view all the answers

    In signal transduction, how do cells interpret incoming signals?

    <p>Using their intracellular machinery for integration</p> Signup and view all the answers

    What characterizes the response of target cells to acetylcholine?

    <p>Responses vary based on intracellular setup</p> Signup and view all the answers

    Which statement about intercellular signaling is accurate?

    <p>Single signal molecules can have broad effects across different cell types</p> Signup and view all the answers

    Which choice best describes the role of receptors in signal transduction?

    <p>Receptors provide specificity to signal responses</p> Signup and view all the answers

    What is the primary function of rapamycin in relation to hepatocellular carcinoma cells?

    <p>It induces apoptosis.</p> Signup and view all the answers

    Which type of receptor is NOT classified as a cell-surface receptor?

    <p>Intracellular receptors</p> Signup and view all the answers

    Which type of signaling is characterized by the release of signals that act on neighboring cells?

    <p>Paracrine signaling</p> Signup and view all the answers

    Why are defective signaling pathways significant in diseases?

    <p>They lead to abnormal growth and function.</p> Signup and view all the answers

    What role do GPCRs play in signal transduction?

    <p>They act as switches to transmit signals.</p> Signup and view all the answers

    What is the primary effect of cholera toxin on G-proteins?

    <p>It prevents Gs from hydrolyzing its GTP-bound state.</p> Signup and view all the answers

    What is the role of CFTR in the context of cholera toxin?

    <p>It facilitates excessive Cl- and H2O outflow.</p> Signup and view all the answers

    Which type of cell surface receptor is known as transmitter-gated ion channels?

    <p>Ion-Channel-Coupled Receptors</p> Signup and view all the answers

    What unique structural feature do G-Protein-Coupled Receptors (GPCRs) possess?

    <p>They feature a seven-pass transmembrane configuration.</p> Signup and view all the answers

    Which of the following statements is true regarding the intrinsic GTPase activity of the α-subunit in GPCRs?

    <p>It hydrolyzes GTP into GDP to switch itself off.</p> Signup and view all the answers

    Which receptor type primarily functions as a tyrosine protein kinase?

    <p>Enzyme-Coupled Receptors</p> Signup and view all the answers

    What is the outcome of signaling through Gαs in skeletal muscle?

    <p>It stimulates adenylyl cyclase.</p> Signup and view all the answers

    Which of the following describes the general importance of signal transduction?

    <p>It regulates various cellular responses.</p> Signup and view all the answers

    Study Notes

    Signal Transduction

    • Signal transduction is the conversion of a signal from one form to another
    • Communication relies on receptors, target cells, and extracellular signals
    • Types of intercellular signaling include endocrine, paracrine, neuronal, and contact-dependent signaling
    • Extracellular signals bind to cell-surface or intracellular receptors, which then activate intracellular signaling molecules
    • G-protein-coupled receptors (GPCRs) activate G-proteins, which transmit the signal and then deactivate
    • Three main types of cell-surface receptors are ion-channel-coupled receptors, G-protein-coupled receptors (GPCRs), and enzyme-coupled receptors
    • Intracellular signaling pathways can lead to altered cell metabolism, cell shape/movement, or gene expression

    Learning Objectives

    • General principles of cell signaling and signal transduction
    • Types of intercellular signaling
    • Chemical nature of signal molecules
    • Different responses of cells to same signal molecules
    • Molecular switching mechanisms in signal transduction
    • Signal transduction through various receptors

    Lecture Outline

    • Definitions
    • General principles of cell signaling and signal transduction
    • Types of intercellular signaling
    • Chemical nature of signal molecules
    • Different responses of cells to the same signal molecule
    • Molecular switching in signal transduction
    • Signal transduction through various receptor types

    Definitions

    • Receptor protein: a protein that recognizes and binds to a specific signal molecule, initiating a physiological response within the cell
    • Extracellular signaling molecule: any molecule present outside the cell that elicits a response when binding to a receptor protein inside the cell
    • Intracellular signaling molecule: a molecule that functions within the cell, acting as part of the mechanism for transducing and transmitting signals within the cell

    General Principles of Cell Signaling

    • Cell-cell communication is vital for both unicellular and multicellular organisms to coordinate behavior; it's essential for growth, development, differentiation, tissue & organ formation, maintenance of homeostasis, and diseases.
    • An example of signaling is the fight-or-flight response, triggered by a signaling molecule like epinephrine.

    Overview of Cell Signaling

    • Signaling molecules (ligands) bind to specific receptor proteins.
    • Reception sets off a relay team (proteins in the cell)
    • Signal transduction occurs, leading to a cellular response. This response can include activating a gene, apoptosis, entering mitosis, etc.

    Signal Transduction

    • Converts information from one form into another
    • Begins when a target cell receives an incoming extracellular (EC) signal and converts into intracellular (IC) signals, altering cell behavior

    Examples of Signaling Molecules & Their Chemical Nature

    • Signal molecules (e.g., epinephrine, cortisol, estradiol, insulin, testosterone, thyroid hormone) vary in chemical nature (e.g., amino acid derivatives, steroids, proteins)
    • They originate in various locations (e.g., adrenal gland, ovary, pancreas, testis, thyroid gland)
    • Depending on the location and chemical makeup some signal molecules elicit different results in various cell types.

    Types of Intercellular Signaling

    • Endocrine signaling: hormones released into the bloodstream to act on distant target cells.
    • Paracrine signaling: local mediators act on nearby target cells.
    • Neuronal signaling: neurotransmitters released across synapses to act on target cells.
    • Contact-dependent signaling: transmembrane signal molecule binds to a receptor protein on a neighboring cell.

    Two Classes of Signal Molecules

    • Hydrophilic or large molecules relay on cell-surface receptors, similar to growth factors.
    • Hydrophobic or small molecules activate enzymes directly or bind to intracellular receptors, such as steroid hormones.

    Example: Steroid Hormones Signaling

    • Hydrophobic nature allows steroid hormones to pass through the plasma membrane
    • They bind to intracellular receptors
    • The activated receptor-hormone complex moves into the nucleus and interacts with DNA to alter gene expression

    Nitric Oxide Crosses the Plasma Membrane and Activates Intracellular Enzymes

    • Nitric oxide (NO) is a small, unstable gas that crosses the plasma membrane.
    • It activates enzymes directly, for example, to treat angina

    Cell-surface Receptors Relay the Signal Through Intracellular Signaling Molecules

    • Simple intracellular signaling pathway.
    • Signal molecules bind to receptors, activating intracellular signaling molecules (e.g., kinases and G-proteins).
    • This can impact cellular metabolism, shape/movement, or gene expression through a chain reaction

    Common Intracellular Signaling Proteins

    • Kinases (switches) activate/inactivate other proteins by phosphorylation.
    • G-proteins (switches) bind GTP and are active, triggering signaling cascades

    Why Molecular Switching is Important in Disease

    • Bacteria toxins, like Cholera toxin, can alter G-proteins, causing catastrophic diarrhea/dehydration.
    • Defective signaling pathways cause or contribute to various diseases.

    Three Main Classes of Cell-Surface Receptors

    • Ion-channel-coupled receptors
    • G-protein coupled receptors (GPCRs)
    • Enzyme-coupled receptors

    Why is Signal Transduction Important

    • Glycogen breakdown in skeletal muscle (fight-or-flight response)
    • Rapamycin inhibits cell growth in cancer.

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    Description

    Test your knowledge on cell signaling mechanisms and signal transduction processes. This quiz covers receptor proteins, signaling molecules, and the importance of signaling in both unicellular and multicellular organisms. Answer questions about the roles and functions in cellular communication.

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