Cell Signaling and Communication
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Questions and Answers

What type of signaling involves molecules released by one cell acting on neighboring target cells?

  • Autocrine signaling
  • Paracrine signaling (correct)
  • Endocrine signaling
  • Juxtacrine signaling

    • Which type of signaling allows cells to respond to signaling molecules that they produce themselves?

  • Autocrine signaling (correct)
  • Exocrine signaling
  • Neurocrine signaling
  • Paracrine signaling

    • What role does abnormal autocrine signaling play in cancer development?

  • It allows cancer cells to self-stimulate their growth. (correct)
  • It helps to enhance immune response.
  • It reduces the spread of malignant cells.
  • It stabilizes cell proliferation.

    • Where are intracellular receptors typically located?

    <p>Inside the cell</p> Signup and view all the answers

    Which hormone is synthesized from cholesterol and classified as a sex steroid?

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

    Which hormone primarily regulates glucose production from the adrenal gland?

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

    What is the primary function of vitamin D3 in the body?

    <p>Regulating Ca2+ metabolism and bone growth</p> Signup and view all the answers

    What is ecdysone known for in the context of insect physiology?

    <p>Triggering metamorphosis in larvae</p> Signup and view all the answers

    What happens when signaling molecules bind to receptors on a cell?

    <p>They initiate a series of reactions regulating cell behavior.</p> Signup and view all the answers

    Which type of signaling involves hormones traveling through the bloodstream to distant target cells?

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

    Which of the following is NOT a characteristic of signaling molecules?

    <p>All are transmitted over long distances.</p> Signup and view all the answers

    What type of cell signaling is characterized by direct interaction between neighboring cells?

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

    How do many cancers relate to cell signaling pathways?

    <p>They can arise from failures in normal signaling pathways.</p> Signup and view all the answers

    Which signaling molecules are considered endocrine signals?

    <p>Hormones secreted by endocrine cells.</p> Signup and view all the answers

    What is the role of receptors in cell signaling?

    <p>They bind signaling molecules and initiate cell responses.</p> Signup and view all the answers

    Which of the following best describes paracrine signaling?

    <p>Signals act on nearby cells in the vicinity.</p> Signup and view all the answers

    Which of the following is NOT a peptide hormone?

    <p>Epidermal growth factor (EGF)</p> Signup and view all the answers

    What is the function of nerve growth factor (NGF)?

    <p>Regulates development and survival of neurons</p> Signup and view all the answers

    What role do cytokines play in the body?

    <p>Regulate development and differentiation of blood cells</p> Signup and view all the answers

    Which of the following plant hormones is responsible for stem elongation?

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

    What type of signaling molecules are enkephalins and endorphins classified as?

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

    What process do membrane-anchored growth factors facilitate?

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

    What occurs after ligand binding to a receptor?

    <p>Initiation of intracellular reactions</p> Signup and view all the answers

    Which growth factor is released during blood clotting and stimulates fibroblast proliferation?

    <p>Platelet-derived growth factor (PDGF)</p> Signup and view all the answers

    What happens to the glucocorticoid receptor when glucocorticoid binds to it?

    <p>It displaces Hsp90 and binds to regulatory DNA sequences.</p> Signup and view all the answers

    Which of the following correctly describes the thyroid hormone receptor in the absence of hormone?

    <p>It is associated with a corepressor complex and represses transcription.</p> Signup and view all the answers

    What defines the action of nitric oxide (NO) as a signaling molecule?

    <p>It is extremely unstable, with a half-life of only a few seconds.</p> Signup and view all the answers

    How do hydrophobic signaling molecules typically regulate gene expression?

    <p>By influencing transcription factors that bind to DNA.</p> Signup and view all the answers

    What role do nuclear receptors play as transcription factors?

    <p>They have multiple domains for ligand binding and DNA binding.</p> Signup and view all the answers

    Which of the following is NOT a type of signaling molecule mentioned?

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

    What is the primary function of paracrine signaling molecules like nitric oxide?

    <p>To alter the activity of enzymes locally.</p> Signup and view all the answers

    Which component is associated with the glucocorticoid receptor in the absence of hormone?

    <p>Hsp90 chaperones</p> Signup and view all the answers

    What is the primary function of cAMP in signaling pathways?

    <p>To mediate effects via protein kinase A</p> Signup and view all the answers

    How does the Gi protein affect heart muscle contraction?

    <p>It opens K+ channels and slows contraction</p> Signup and view all the answers

    What is the role of protein kinase A in glycogen metabolism?

    <p>To phosphorylate and activate glycogen phosphorylase</p> Signup and view all the answers

    What triggers the formation of cAMP from ATP?

    <p>Adenylyl cyclase</p> Signup and view all the answers

    What is a consequence of cAMP binding to the regulatory subunits of protein kinase A?

    <p>Activation of the catalytic subunits</p> Signup and view all the answers

    What effect does cAMP have on glycogen synthase?

    <p>It inhibits glycogen synthase activity</p> Signup and view all the answers

    Who discovered the role of cAMP as a second messenger, and in what year?

    <p>Sutherland in 1958</p> Signup and view all the answers

    What are the products of cAMP degradation?

    <p>AMP and phosphates</p> Signup and view all the answers

    What is the primary role of ligand binding to receptor tyrosine kinases?

    <p>To activate cytosolic kinase domains</p> Signup and view all the answers

    What is the consequence of receptor dimerization?

    <p>Autophosphorylation of the receptors</p> Signup and view all the answers

    What role does autophosphorylation play in receptor tyrosine kinases?

    <p>It creates binding sites for other signaling proteins</p> Signup and view all the answers

    Which domain is recognized for binding to phosphotyrosine-containing peptides?

    <p>SH2 (Src homology 2)</p> Signup and view all the answers

    What is an immediate effect of the phosphorylation of tyrosine in the catalytic domain of a receptor?

    <p>Increased protein kinase activity</p> Signup and view all the answers

    What is a key characteristic of nonreceptor tyrosine kinases?

    <p>They stimulate intracellular tyrosine kinases</p> Signup and view all the answers

    Which statement is true regarding the structure of receptor tyrosine kinases?

    <p>They possess a cytosolic domain with protein-tyrosine kinase activity</p> Signup and view all the answers

    How do growth factors interact with receptor tyrosine kinases?

    <p>They bind to extracellular domains and activate the receptors</p> Signup and view all the answers

    Study Notes

    Cell Signaling

    • Cells respond to signals from their environment.
    • Bacteria and single-celled eukaryotes respond to environmental signals and signals from other cells.
    • In multicellular organisms, cell-cell communication is complex and each cell must be regulated to meet the needs of the whole organism.
    • Signaling molecules, secreted or on the surface of one cell, bind to receptors on other cells.
    • Binding of signaling molecules initiates a series of reactions that regulate cell behavior.
    • Many cancers arise from problems in signaling pathways that control cell proliferation.

    Signaling Molecules and Their Receptors

    • Signaling molecules range from simple gases to proteins.
    • Some signals travel long distances, others act locally.
    • Some molecules cross the plasma membrane and bind to intracellular receptors. Others bind to receptors on the cell surface.
    • Modes of cell signaling: Direct cell-cell signaling involves interaction with neighboring cells (e.g., via integrins and cadherins). Signaling by secreted molecules is categorized by the distance the signal travels.

    Endocrine Signaling

    • Hormones are secreted molecules carried via the circulatory system to distant target cells.
    • Example: estrogen

    Paracrine Signaling

    • Molecules released by one cell act on neighboring target cells.
    • Example: neurotransmitters

    Autocrine Signaling

    • Cells respond to signaling molecules they produce themselves.
    • Example: T lymphocytes respond to antigens by producing growth factors that stimulate their own proliferation and strengthen the immune response.
    • Abnormal autocrine signaling contributes to cancer.

    Intracellular Receptors

    • Intracellular receptors respond to small, hydrophobic molecules that can diffuse across the plasma membrane.
    • Examples include steroid hormones, thyroid hormone, vitamin D, and retinoic acid.

    Steroid Hormones

    • Steroid hormones are synthesized from cholesterol.
    • Testosterone, estrogen, and progesterone are sex steroids produced by the gonads.
    • Other examples: Corticosteroids (glucocorticoids and mineralocorticoids) from the adrenal gland.
      • Glucocorticoids stimulate glucose production.
      • Mineralocorticoids regulate salt and water balance in the kidneys.
    • Other examples: ecdysone (insect hormone) and brassinosteroids (plant hormones).

    Thyroid Hormone, Vitamin D3, and Retinoic Acid

    • Thyroid hormone is synthesized from tyrosine in the thyroid gland and plays a role in development and metabolism.
    • Vitamin D3 regulates calcium metabolism and bone growth.
    • Retinoic acid and retinoids are synthesized from vitamin A and are important in vertebrate development.
    • All are members of the nuclear receptor superfamily.
    • These hormones directly regulate gene expression.

    Ligand Binding and Receptor Activity

    • Ligand binding affects receptors differently.
    • Some receptors are inactive in the absence of a hormone.
      • Examples include the glucocorticoid receptor, which is bound to Hsp90 chaperones until a hormone binds .
    • Hormone binding changes receptor activity.
      • In the absence of a hormone, the thyroid hormone receptor is associated with a corepressor complex. Binding of a hormone activates transcription.

    G Proteins and Cyclic AMP Signaling

    • G protein-coupled receptors are the largest family of cell surface receptors.
    • Signals are transmitted via G proteins (guanine nucleotide-binding proteins).
    • G proteins have three subunits (α, β, γ).
    • In the inactive state, the α subunit is bound to GDP.
    • Hormone binding causes GTP to exchange for GDP, causing the α and βγ subunits to dissociate from the receptor.
    • The separated subunits then interact with their target molecules.
    • A hormone binding to the receptor induces intracellular changes which trigger downstream pathways to reach the nucleus and change gene expression.
    • Cyclic AMP (cAMP) is a second messenger that mediates responses to many hormones.

    cAMP-Dependent Signaling

    • cAMP activates protein kinase A (PKA).
    • The inactive PKA consists of two regulatory and two catalytic subunits.
    • cAMP binds to the two regulatory subunits, causing them to dissociate and activate the catalytic subunits.
    • The activated catalytic subunits can then phosphorylate serine on target proteins.

    Signal Amplification

    • Binding of a hormone molecule leads to the activation of many intracellular enzymes.
    • In epinephrine signaling, one molecule of epinephrine can activate up to 100 molecules of Gs.

    Kinase and Phosphatase Regulation

    • Protein kinases aren’t isolated and require phosphatases to reverse phosphorylation.
    • cAMP can also directly regulate ion channels.
    • Receptor and non-receptor tyrosine kinases are important in cell signaling and are directly linked to intracellular enzymes.
    • Receptor Tyrosine Kinases are the dominant family and includes receptors for most polypeptide growth factors.
    • Receptor tyrosine kinases have an extracellular ligand-binding domain, one transmembrane helix, and a cytosolic C-terminal domain with protein-tyrosine kinase activity.
    • Ligand binding induces receptor dimerization, leading to autophosphorylation.
    • Autophosphorylation creates binding sites for downstream signaling molecules with SH2 domains.
    • Downstream signaling involves activation of intracellular tyrosine kinases.
    • Cytokine receptors are similar to receptor tyrosine kinases structuraly. Differences include the lack of catalytic activity in the cytosolic domains

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    Cell Signaling Lecture Notes PDF

    Description

    This quiz explores the intricate world of cell signaling, focusing on how cells communicate with their environment and each other. It covers the role of signaling molecules, their receptors, and the implications of signaling pathways in health and disease, particularly cancer. Test your understanding of these essential biological processes!

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