Cellular Signaling and Signal Transduction
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Questions and Answers

What role do steroid-receptor complexes play in cellular processes?

  • They act as signal amplifiers.
  • They act as transcription factors. (correct)
  • They deactivate protein kinases.
  • They inhibit gene transcription.

    • What is the primary function of the ras protein in cellular signaling?

  • It acts as a transcription factor.
  • It activates protein kinase cascades. (correct)
  • It inhibits tyrosine kinase activity.
  • It deactivates second messengers.

    • How do protein kinases contribute to signal transduction?

  • By phosphorylating target proteins. (correct)
  • By binding directly to ligand-gated channels.
  • By inhibiting calcium ion entry.
  • By generating second messengers.

    • What occurs if there is a mutation in the gene for the ras protein?

    <p>Ras is activated without growth factor.</p> Signup and view all the answers

    Which of the following is a primary second messenger in cellular signaling?

    <p>Calcium ion (Ca+2)</p> Signup and view all the answers

    What catalyzes the formation of cyclic AMP from ATP?

    <p>G-protein activated adenylyl cyclase</p> Signup and view all the answers

    What happens to the concentration of calcium ions (Ca+2) in the cytoplasm during signaling?

    <p>It increases through release from the endoplasmic reticulum.</p> Signup and view all the answers

    What is the consequence of deactivating protein kinases in the signaling pathway?

    <p>Termination of the signaling cascade.</p> Signup and view all the answers

    What is the primary function of receptor tyrosine kinases when a signaling ligand binds to them?

    <p>They transfer phosphate groups between macromolecules.</p> Signup and view all the answers

    What happens when a ligand binds to a ligand-gated ion channel?

    <p>The channel opens, allowing specific ions to enter the cell.</p> Signup and view all the answers

    How does phosphorylation generally affect a protein's activity?

    <p>It can change the protein's shape, affecting its function.</p> Signup and view all the answers

    What role does the Ras oncogene play in cell signaling?

    <p>It acts as a G-protein that propagates signals.</p> Signup and view all the answers

    What is a common consequence of disruptions in receptor tyrosine kinase pathways?

    <p>Development of various cancers.</p> Signup and view all the answers

    What distinguishes second messengers from primary signaling molecules?

    <p>Second messengers act inside the cell after the primary signal.</p> Signup and view all the answers

    What occurs during the formation of a dimeric protein in receptor tyrosine kinases?

    <p>Two protein monomers combine upon ligand binding.</p> Signup and view all the answers

    What is a characteristic of hydrophobic signaling molecules?

    <p>They can cross the cell membrane to bind their receptor inside the cell.</p> Signup and view all the answers

    What occurs when a ligand binds to its receptor on a target cell?

    <p>The receptor undergoes a change in shape.</p> Signup and view all the answers

    Which of the following is NOT a function of receptor tyrosine kinases?

    <p>Activation of G-proteins.</p> Signup and view all the answers

    In signal transduction, what is the role of a phosphorylation cascade?

    <p>It amplifies the signal within the cell.</p> Signup and view all the answers

    What is a common effect of second messengers in signal transduction pathways?

    <p>They mediate the transmission of signals from receptors.</p> Signup and view all the answers

    Which mechanism allows cells to respond specifically to chemical signals?

    <p>Expression of specific receptor proteins on target cells.</p> Signup and view all the answers

    How does the Ras oncogene contribute to cell signaling?

    <p>It functions as a molecular switch in signaling pathways.</p> Signup and view all the answers

    What is the primary role of ligand-gated ion channels in cellular signaling?

    <p>They facilitate rapid changes in ion concentrations.</p> Signup and view all the answers

    What typically happens in a cell when the ligand binds to a receptor in the process of signal transduction?

    <p>The receptor triggers a series of intracellular responses.</p> Signup and view all the answers

    Study Notes

    Cellular Signaling and Signal Transduction

    • Cell communication is crucial for cell function. Cells exchange key molecules directly.
    • Gap junctions facilitate communication between animal cells, and plasmodesmata do the same for plant cells.

    Cell-Cell Recognition

    • Surface ligands on one cell bind to receptors on another cell, triggering a response in the target cell.

    Cellular Communication by Released Molecular Signals

    • Yeast cells, for sexual reproduction, have different mating types ("A" and "alpha").

    • "A" cells release "A" mating factor (recognized by "alpha" cells), and vice versa.

    • Fusion of cells results in diploid cells and meiosis (genetic recombination).

    • Myxococcus bacteria, when nutrients are scarce, form structures to survive.

    • This involves chemical signaling between individual cells enabling their collective action.

    • Single-celled eukaryotes utilize similar mechanisms.

    Signal Transduction

    • Cell membranes receive and absorb chemical signals from outside the cell.

    • These signals alter cellular functions and gene expression.

    • Signal transduction is essential for multicellular organisms.

    • Cells respond only if they have appropriate receptor proteins for the signal.

    • Ligand binding to a receptor changes the receptor's shape, triggering intracellular responses.

    • These responses lead to the appropriate cellular responses.

    Types of Signals and Receptors

    • Signals can be short-range and long-range.
      • Short-range: paracrine, synaptic
      • Long-range: endocrine
    • G protein-coupled receptors (GPCRs) are transmembrane proteins that use GTP.
    • Important for embryonic development, sensory functions, and responses to infections.
    • Receptor tyrosine kinases are activated by dimerization (two monomers coming together).
    • Tyrosine kinases phosphorylate other proteins, triggering a cellular response, particularly involved in cancer.
    • Important for cell growth and division.
    • Ion channels are receptors that allow ion flow.
    • Steroid hormones are examples of hydrophobic signals that interact with intracellular protein receptors (intracellular signaling).

    Signal Transduction Pathways

    • Signal transduction often uses a cascade of protein activations.

    • This amplifies the initial signal.

    • Protein kinases phosphorylate proteins, and phosphatases dephosphorylate them.

    • This allows reversible activation and responses.

    • Signal pathways use second messengers like calcium ions (Ca²⁺) and cyclic AMP (cAMP).

    • These second messengers amplify and distribute signals quickly.

    • The goal of signal transduction is often to alter gene expression.

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    Related Documents

    Cellular Signaling / Signal Transduction PDF

    Description

    Explore the fascinating world of cellular communication and signal transduction mechanisms. Learn how cells interact through gap junctions, cell recognition, and molecular signals to coordinate functions. This quiz will test your knowledge on key concepts in cellular signaling.

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