Cell Signal Transduction and Signalling Types
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Questions and Answers

What is the primary function of cyclic guanosine monophosphate (cGMP) as a second messenger?

  • Enhancing mitochondrial respiration.
  • Regulating gene expression.
  • Facilitating smooth muscle contraction. (correct)
  • Calcium ion storage.

    • Which of the following is NOT an example of a second messenger?

  • Cholesterol (correct)
  • Cyclic guanosine monophosphate (cGMP)
  • Cyclic adenosine monophosphate (cAMP)
  • Inositol trisphosphate (IP3)

    • Which gas is considered a second messenger that can signal to neighboring cells?

  • Hydrogen sulphide (H2S)
  • Carbon monoxide (CO)
  • Ozone (O3)
  • Nitric oxide (NO) (correct)

    • Which of the following ions can act as a second messenger within cellular compartments?

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

    What structural component is featured in the cyclic structures of cyclic monophosphates such as cAMP and cGMP?

    <p>A cyclic bond with a phosphate group.</p> Signup and view all the answers

    What best defines cell signal transduction?

    <p>The mechanism through which a cell responds to external chemical signals.</p> Signup and view all the answers

    Which of the following is a type of intercellular signaling?

    <p>Communication between neighboring cells.</p> Signup and view all the answers

    What role do ligands play in cell signaling?

    <p>They bind to specific receptors to trigger a biological response.</p> Signup and view all the answers

    Which of the following statements about receptors is true?

    <p>Receptors are essential for cellular communication and response.</p> Signup and view all the answers

    Which of the following is NOT a step in the process of intercellular signaling?

    <p>Receptor activation in the nucleus.</p> Signup and view all the answers

    What distinguishes intracellular signaling from intercellular signaling?

    <p>Intracellular signaling occurs in one cell while intercellular involves multiple cells.</p> Signup and view all the answers

    Which molecule is an example of a second messenger in cell signaling?

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

    What is the primary function of carrier proteins in cell signaling?

    <p>They facilitate the transport of the signal to the target cell.</p> Signup and view all the answers

    What is the primary role of specific receptors in signal reception?

    <p>To detect chemical signals and activate intracellular signaling pathways.</p> Signup and view all the answers

    Which of the following accurately describes transduction in signal transduction pathways?

    <p>The signal is converted into a biochemical response through a series of relays.</p> Signup and view all the answers

    How does the endocrine signaling differ from paracrine signaling?

    <p>Endocrine signaling involves hormones released into the bloodstream, while paracrine signaling acts locally.</p> Signup and view all the answers

    Which type of cellular signaling involves the quickest responses?

    <p>Paracrine signaling, facilitating rapid diffusion between adjacent cells.</p> Signup and view all the answers

    What initiates the intracellular signaling pathways after signal reception?

    <p>A change in the shape of the receptor after ligand binding.</p> Signup and view all the answers

    What is NOT a characteristic of endocrine signaling?

    <p>Stimulates immediate local response in neighboring cells.</p> Signup and view all the answers

    What type of signaling connects cells directly, allowing for immediate response?

    <p>Direct signaling across gap junctions.</p> Signup and view all the answers

    What is the function of protein kinases in signal transduction?

    <p>To add phosphate groups to proteins, thereby amplifying the signal.</p> Signup and view all the answers

    What is the primary function of autocrine signaling?

    <p>To allow a cell to signal itself or similar cells</p> Signup and view all the answers

    Which type of signal can pass through gap junctions during direct signaling?

    <p>Small ions like calcium (Ca2+)</p> Signup and view all the answers

    What is the role of internal receptors in cellular signaling?

    <p>To respond to hydrophobic ligands that cross the plasma membrane</p> Signup and view all the answers

    Which process involves the addition of a phosphate group to a protein, potentially altering its function?

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

    What characterizes enzyme-linked receptors in cell signaling?

    <p>They have an intracellular domain that acts as an enzyme.</p> Signup and view all the answers

    What mechanism do G-protein-linked receptors use to propagate cellular signals?

    <p>They activate G-proteins that then interact with other membrane proteins.</p> Signup and view all the answers

    Which of the following is NOT a type of cell-surface receptor?

    <p>Cytoskeletal Receptors</p> Signup and view all the answers

    What is the main role of second messengers in intracellular signaling?

    <p>To amplify and propagate the initial signal received by a receptor.</p> Signup and view all the answers

    Study Notes

    Cell Signal Transduction

    • The process of how a cell responds to external chemical signals.
    • Crucial for communication between cells and regulating various biological processes.

    Cell Signalling Types

    • Intercellular signalling: Communication between cells
    • Intracellular signalling: Signalling chains within the cell, responding to extracellular and intracellular stimuli

    Intercellular Signalling in Eukaryotes

    • Coordinates vital functions, ensuring maintenance and function of specialized tissues and organs.
    • Functions include cell growth, division, motility, and morphology.

    Signalling Receptors

    • Protein molecules that bind to ligands, initiating a cellular response.
    • Ligands are molecules that attach to specific receptors on a cell to trigger a biological response.
    • Ligands act as "keys" that bind to "locks" (receptors) on the cell.
    • A specific ligand will have a specific receptor.
    • Receptors are essential for cell communication and response.

    Steps of Intercellular Signalling

    • Formation: An external trigger causes the production/release of signaling molecules (e.g., hormones) from specialized cells.
    • Signal Transport: The signal travels to the target cell, often via circulation or diffusion, sometimes with carrier proteins.
    • Signal Reception: The target cell receives the signal through specific receptors, initiating intracellular signaling pathways.
    • Signal Processing: The signal is converted into a biochemical response within the target cell, leading to specific cellular actions.

    Stages of Cellular Signal Transduction

    • Reception: Cells detect chemical signals through receptors.
    • Transduction: The signal is converted into an internal response. Ligand binds to the receptor, changing the receptor's shape and activating the cell. Signal pathways often involve relay molecules that further amplify the signal.
    • Response: The cell performs a specific action in response to the signal. Actions could include changes in gene expression, enzyme activity, or cell metabolism. Examples include protein kinases adding phosphate groups to proteins, or cell division, muscle contraction, or apoptosis.

    Forms of Chemical Cell Signalling

    • Paracrine: Signals act locally between nearby cells. Signals move by diffusion through the extracellular matrix. Elicit quick, short-lasting responses.
    • Endocrine: Signals originate from distant endocrine cells. Located in endocrine glands like the thyroid, hypothalamus, and pituitary. Produce slower, longer-lasting effects. Hormones are released by glands into the bloodstream, where they travel long distances to target cells in different parts of the body.
    • Autocrine: Signals produced and responded to by the same cell or similar cells. Signaling cell releases a signal that binds to its own receptors. Ensures proper tissue formation and function during early development.
    • Direct signalling across gap junctions: Direct communication between neighboring cells through water-filled channels. Gap junctions in animals, plasmodesmata in plants. Small molecules like calcium ions (Ca2+) can pass through; larger molecules cannot.

    Types of Receptors

    • Internal Receptors: Found in the cytoplasm or nucleus. Respond to hydrophobic ligands that cross the plasma membrane. Regulate gene expression by binding to DNA after a ligand-induced conformational change.
    • Cell-Surface Receptors: Transmembrane receptors. Bind external ligands without the ligands entering the cell. Specific to cell types and convert extracellular signals into intracellular actions.

    Types of Cell-Surface Receptors

    • Ion Channel-Linked Receptors: Open a channel through the membrane when a ligand binds, allowing specific ions to pass through and alter the cell's activity. Example: acetylcholine (nicotine receptor).
    • G-Protein-Linked Receptors: Activate G-proteins upon ligand binding, which then interact with other membrane proteins to propagate the signal. G-proteins switch between active and inactive states to regulate cellular responses. Example: Dopamine.
    • Enzyme-Linked Receptors: Have an intracellular domain that acts as an enzyme or associates with an enzyme. Ligand binding activates the enzyme, triggering a cascade of cellular events. Example: insulin receptor.

    Examples of Common Events in Intracellular Signalling

    • Phosphorylation: Adding a phosphate group to a protein by an enzyme called kinase, which can activate or deactivate the protein.
    • Second Messengers: Intracellular, diffusible small molecules and ions that are quickly synthesized or released in response to signals from receptors, altering the activity of target signalling proteins.

    Second Messengers (Examples)

    • Cyclic nucleotides: Cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP)
    • Lipid messengers: Originate within cell membranes, including inositol trisphosphate (IP3).
    • Gases: Can signal throughout the cell and even to neighboring cells. Includes NO, CO, hydrogen sulphide (H2S).
    • Ions: Signal within and between cellular compartments, including calcium (Ca2+), Na+, and K+.

    cGMP (Cyclic Guanosine Monophosphate)

    • Structure: Nucleotide with a sugar, guanine base, and a single phosphate group in a cyclic bond.
    • Function: Second messenger in processes like smooth muscle contraction, phototransduction in the eye, and blood vessel dilation.

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    Cell Signalling PDF

    Description

    Explore the intricate process of cell signal transduction and the different types of cell signalling. Learn how cells communicate with each other through intercellular and intracellular signalling, along with the importance of receptors and ligands. Discover how these processes regulate critical biological functions in eukaryotic organisms.

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