Cell-Cell Communication and Chemical Messengers
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Cell-Cell Communication and Chemical Messengers

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Questions and Answers

What role does the signaling cell play in cellular communication?

  • It receives the signals from the target cell.
  • It sends a chemical signal to the target cell. (correct)
  • It responds to external stimuli.
  • It acts as a receptor for incoming signals.

    • Which of the following are types of stimuli that cells can detect?

  • Chemical but not physical
  • Visual and auditory
  • Light and mechanical pressure (correct)
  • Electrical and thermal

    • What is the primary function of the receptor in cell signaling?

  • To send signals to other cells.
  • To detect specific stimuli in the extracellular environment. (correct)
  • To perform programmed cell death.
  • To convert internal signals into external responses.

    • Which process refers to the programmed cell death in animals?

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

    In which scenario would a cell undergo positive chemotaxis?

    <p>When moving towards a food source.</p> Signup and view all the answers

    What happens during signal transduction in cellular communication?

    <p>External environmental signals are converted into internal cellular signals.</p> Signup and view all the answers

    What type of signaling involves direct communication between adjacent cells?

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

    Which cellular process would be most likely altered by changes in receptor-ligand interactions?

    <p>Cell growth and differentiation</p> Signup and view all the answers

    What is the role of E kinase in the feedback loop described?

    <p>E kinase phosphorylates itself and I</p> Signup and view all the answers

    How does positive feedback affect a cellular response?

    <p>It may cause prolonged activation of the response</p> Signup and view all the answers

    What occurs during cell adaptation or desensitization?

    <p>The cell's response decreases due to prolonged exposure to the stimulus</p> Signup and view all the answers

    Which of the following best describes signal transduction?

    <p>The change of an extracellular signal into an intracellular one</p> Signup and view all the answers

    What effect does I have on E kinase in the feedback loop?

    <p>It decreases the activity of E kinase while oscillating</p> Signup and view all the answers

    Which of the following cellular processes is NOT regulated by intracellular signals?

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

    What mechanism can cells use to adjust their sensitivity to signals?

    <p>Cell adaptation or desensitization</p> Signup and view all the answers

    What is a potential outcome of prolonged activity of E kinase?

    <p>Intermittent oscillation of signaling activity</p> Signup and view all the answers

    What is the primary function of chemical messengers in indirect signaling?

    <p>To bind to receptors on target cells and initiate a response</p> Signup and view all the answers

    Which type of indirect signaling involves a chemical messenger diffusing back to the signaling cell?

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

    What distinguishes endocrine signaling from paracrine signaling?

    <p>Endocrine signaling is slower and uses the circulatory system</p> Signup and view all the answers

    How do hormones primarily communicate within the body?

    <p>By being secreted into the circulatory system</p> Signup and view all the answers

    Which type of signaling is characteristic of rapid and transient communication in animals?

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

    What role do pheromones play in communication among animal species?

    <p>They are chemical signals released into the environment</p> Signup and view all the answers

    In which biological system do hormones mainly function?

    <p>The endocrine system</p> Signup and view all the answers

    Which of the following statements about autocrine signaling is true?

    <p>It plays a significant role in the immune system</p> Signup and view all the answers

    What characterizes steroids in the context of hormone function?

    <p>They require carrier proteins for circulation in the bloodstream.</p> Signup and view all the answers

    Which statement about sex hormones and SHBG is correct?

    <p>SHBG influences the bioavailability of sex hormones.</p> Signup and view all the answers

    Which of the following is an example of a biogenic amine?

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

    How does testosterone primarily exert its effects on target cells?

    <p>By binding to intracellular receptors for gene transcription.</p> Signup and view all the answers

    What is a primary role of eicosanoids in the body?

    <p>They are often involved in inflammation and pain.</p> Signup and view all the answers

    Which statement correctly reflects the characteristics of biogenic amines?

    <p>Biogenic amines possess an amine group (–NH2).</p> Signup and view all the answers

    What is the average fraction of biologically active unbound testosterone in circulation?

    <p>1-2%</p> Signup and view all the answers

    Which of the following describes the role of gases like nitric oxide in the body?

    <p>They act as paracrines in signaling pathways.</p> Signup and view all the answers

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

    <p>It opens a channel for ion diffusion.</p> Signup and view all the answers

    Which statement accurately describes receptor enzymes?

    <p>They initiate a phosphorylation cascade when a ligand binds.</p> Signup and view all the answers

    What occurs when epinephrine binds to receptors on liver cells?

    <p>It results in the breakdown of glycogen.</p> Signup and view all the answers

    How do lipid-soluble hormones primarily affect target cells?

    <p>By diffusing through the membrane and changing gene expression.</p> Signup and view all the answers

    What is a secondary effect of G-proteins dissociating within a cell?

    <p>They activate second messengers like cAMP.</p> Signup and view all the answers

    Where does the hormone-receptor complex migrate after binding of a steroid hormone?

    <p>Into the nucleus.</p> Signup and view all the answers

    What triggers the activation of specific intracellular proteins in receptor enzymes?

    <p>Binding of a ligand to the receptor.</p> Signup and view all the answers

    What is the function of second messengers produced by G-protein-coupled receptors?

    <p>They amplify the cellular response to signals.</p> Signup and view all the answers

    Study Notes

    Cell-Cell Communication

    • Communication between cells is essential for multicellular organisms.
    • Cells communicate by using signals, typically chemical messengers.
    • Signals can be transmitted directly from one cell to another or indirectly through the extracellular environment.

    Types of Chemical Messengers

    • Steroids are hydrophobic molecules that can diffuse across cell membranes.
      • Examples include testosterone and cortisol.
      • Steroids bind to intracellular or transmembrane receptors and can trigger a slow response by altering gene expression.
    • Biogenic amines possess an amine group (–NH2)
      • Examples include acetylcholine, dopamine, norepinephrine, epinephrine, serotonin, melatonin, histamine, and thyroid hormones.
      • They have diverse effects and can act as hormones, neurotransmitters, or both.
    • Eicosanoids are synthesized from fatty acids in cell membranes and act as paracrines.
      • They can be hydrophobic.
      • Examples include prostaglandins and leukotrienes.
    • Gases are paracrines that can diffuse across cell membranes.
      • Examples include nitric oxide (NO) and carbon monoxide.
    • Purines act as neuromodulators and paracrines.
      • Examples include adenosine, AMP, ATP, and GTP.

    Receptor-Ligand Interactions

    • Ligand-Gated Ion Channels open a channel when a ligand binds to a transmembrane receptor.
      • The movement of ions across the membrane changes the membrane potential.
      • An example is acetylcholine.
    • Receptor Enzymes have a catalytic domain that starts a phosphorylation cascade upon ligand binding to a transmembrane receptor.
      • This cascade initiates a change in the cell.
      • An example is insulin binding to its receptor.
    • G-Protein-Coupled Receptors interact with intracellular GTP binding proteins upon ligand binding to a transmembrane receptor.
      • Subunits of the G-protein dissociate and activate other membrane-associated proteins, producing second messengers (e.g. cAMP).

    Indirect Signaling

    • Paracrine signals diffuse to nearby cells.
    • Autocrine signals diffuse back to the signaling cell.
    • Endocrine signals are hormones transported by the circulatory system.
    • Nervous signals travel along neurons and release neurotransmitters.

    Feedback Loops

    • Positive feedback amplifies the signal and can cause a response to continue long after the stimulus is removed.
    • Negative feedback dampens the signal, reducing the intensity and duration of the response.

    Cell Adaptation / Desensitization

    • Prolonged exposure to a stimulus can cause a decrease in the cell's response to it.
    • This occurs due to receptor downregulation, changes in signal transduction pathways, or other mechanisms.

    Cell Communication Pathways

    • Water-soluble hormones bind to receptors on the plasma membrane.
      • This triggers a signaling cascade that can involve second messengers, enzymes, and changes in gene expression.
      • An example is epinephrine binding to liver cells, causing the release of glucose into the bloodstream.
    • Lipid-soluble hormones diffuse across cell membranes and bind to receptors in the cytoplasm or nucleus.
      • They typically regulate gene expression.
      • An example is a steroid hormone binding to its receptor and moving into the nucleus to act as a transcription factor.

    Endocrine System

    • The endocrine system is responsible for secreting hormones into the bloodstream.
    • These hormones regulate various physiological processes, development, and behavior.

    Pheromones

    • Pheromones are chemical signals released into the environment that can be detected by other individuals of the same species.
      • They often play a role in communication, especially during reproduction.

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    Description

    This quiz explores the vital process of communication between cells in multicellular organisms. It covers various types of chemical messengers, including steroids, biogenic amines, and eicosanoids, along with their functions and examples. Test your knowledge of the mechanisms and importance of cell signaling.

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