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Endocrinology Receptor Pathways Quiz
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Endocrinology Receptor Pathways Quiz

Created by
@WarmNihonium

Questions and Answers

What is the structure of a G protein-coupled receptor (GPCR)?

  • Single membrane spanning protein
  • Receptor with seven transmembrane helices (correct)
  • Lipid-anchored protein
  • Double membrane structure

    • Where are the binding sites for ligands located in a GPCR?

  • Extracellular regions or between helices (correct)
  • Cytoplasmic membrane only
  • Within the nucleus
  • Intracellularly only

    • What effect can activated protein kinase A (pkA) have following GPCR activation?

  • Reduction in DNA replication
  • Regulation of metabolic pathways (correct)
  • Inhibition of glycolysis
  • Decrease in cell membrane permeability

    • Which function is NOT associated with the phosphorylation effects of pkA?

    <p>Inhibition of protein synthesis</p> Signup and view all the answers

    Which of the following best describes GPCRs' interaction with G proteins?

    <p>GPCRs have an intracellular binding site for G proteins</p> Signup and view all the answers

    How does the phosphorylation of channel proteins affect the cell?

    <p>It alters membrane permeability for different ions</p> Signup and view all the answers

    What property do water-soluble proteins have that prevents them from easily penetrating the cell membrane?

    <p>They are charged and relatively big in size.</p> Signup and view all the answers

    Which type of hormone requires a receptor on the cell membrane to exert its effects?

    <p>Water-soluble hormones</p> Signup and view all the answers

    Which hormone is classified as a lipid-soluble hormone?

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

    What is the function of GTPase in the context of G protein-coupled receptors?

    <p>To remove a phosphate and turn off the G protein.</p> Signup and view all the answers

    What is the role of adenylate cyclase in the signaling pathway initiated by G proteins?

    <p>Converts ATP to cAMP.</p> Signup and view all the answers

    What is the 'off' state of the receptor characterized by?

    <p>G protein is bound to GDP</p> Signup and view all the answers

    What happens to the G protein when a peptide hormone binds to the receptor?

    <p>The G protein is activated and GTP is added</p> Signup and view all the answers

    Which statement correctly describes a property of lipid-soluble hormones?

    <p>They bind to receptors inside the cell.</p> Signup and view all the answers

    Which of the following hormones is NOT classified as a steroid hormone?

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

    Which of the following is NOT a peptide hormone?

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

    What characterizes water-soluble hormones in contrast to lipid-soluble hormones?

    <p>They utilize second messenger systems.</p> Signup and view all the answers

    What indicates the 'on' state of the receptor?

    <p>GDP is removed and GTP is added</p> Signup and view all the answers

    Which of the following hormones is included in the list of peptide hormones?

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

    What role does GTP play in the function of the G protein?

    <p>It activates the G protein</p> Signup and view all the answers

    Which type of receptor is primarily associated with the described G protein pathways?

    <p>G protein-coupled receptors</p> Signup and view all the answers

    What is the consequence of the activated G protein moving along the membrane?

    <p>It activates downstream signaling pathways</p> Signup and view all the answers

    What happens when IP3 binds to its specific receptor on the reticulum?

    <p>It opens a channel allowing calcium to exit the reticulum.</p> Signup and view all the answers

    What role does calcium play in the mechanism used by oxytocin?

    <p>It binds to Calmodulin to activate kinases.</p> Signup and view all the answers

    Which enzyme is responsible for breaking down cAMP to regulate signal pathways?

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

    Where are peptide hormones, such as oxytocin, primarily located?

    <p>On the cell membrane</p> Signup and view all the answers

    Which of these is NOT a peptide hormone?

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

    What initiates muscle contractions in the context of calcium signaling?

    <p>The phosphorylation of myosin by kinases.</p> Signup and view all the answers

    What is the state of receptors for steroid hormones when activated?

    <p>In the cytosol or nucleus</p> Signup and view all the answers

    Which hormone is peptide in nature?

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

    Which mechanism prevents persistent activation of signaling pathways in cells?

    <p>Activation of phosphodiesterase.</p> Signup and view all the answers

    Which hormone is steroid in nature?

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

    What is a typical property of peptide hormones?

    <p>Water soluble</p> Signup and view all the answers

    What is a typical property of steroid hormones?

    <p>Can bind to intranuclear receptors</p> Signup and view all the answers

    Which enzyme activates the GPCR?

    <p>Adenylate Cyclase</p> Signup and view all the answers

    Which of the following is NOT a property of peptide hormones?

    <p>Can freely pass through cell membranes</p> Signup and view all the answers

    Which hormone is primarily involved in glucose metabolism and is peptide in nature?

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

    What type of receptor do steroid hormones typically interact with?

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

    Study Notes

    Hormones

    • Peptide hormones include oxytocin, insulin, glucagon, FSH, LH, GH, PTH, and ADH.
    • Peptide hormones are water-soluble, hydrophilic, and large, preventing them from freely crossing the phospholipid bilayer.
    • Require receptors on the cell membrane and utilize 2nd Messenger Systems (Gs, Gq, Gi).
    • Steroid hormones include testosterone, estrogen, progesterone, aldosterone, cortisol, and gonadocorticoids.
    • Steroid hormones are lipid-soluble, derived from cholesterol, and can pass through cell membranes to bind with intracellular receptors.

    G Protein-Coupled Receptors (GPCR)

    • GPCRs have a structure comprising seven transmembrane helices.
    • Binding sites for ligands are external, with intracellular sites for G proteins.
    • The G protein is normally bound to GDP in an inactive state; hormone binding switches it to an active state by exchanging GDP for GTP.
    • Activated G proteins move along the membrane to interact with effector enzymes like adenylate cyclase.

    Adenylate Cyclase and cAMP

    • Activated G stimulatory (Gs) protein activates adenylate cyclase, increasing its activity.
    • Adenylate cyclase converts ATP to cyclic AMP (cAMP); GTPase activity of Gs turns GTP back to GDP, deactivating the G protein.
    • cAMP activates Protein Kinase A (PKA), which phosphorylates various proteins, influencing:
      • Membrane permeability for ions through channel proteins.
      • Metabolic pathways including glycolysis by phosphorylating enzymes.
      • Gene transcription and cell proliferation via phosphorylation of transcription factors.

    Calcium and Calmodulin

    • Calcium ions (Ca²⁺) activate calmodulin, leading to kinase activation for downstream effects.
    • This mechanism, notably used by oxytocin, enhances intracellular calcium levels to trigger contractions.

    Inhibition Mechanisms

    • Phosphodiesterase (PDE) breaks down cAMP to regulate signaling pathways, preventing continuous activation.
    • Phospholipase C may also contribute to inhibition of pathways.

    Summary of Hormone Characteristics

    • Peptide hormones (e.g., oxytocin, insulin) are water-soluble and act on cell membranes.
    • Steroid hormones (e.g., testosterone, cortisol) are lipid-soluble and act within the cell or nucleus.

    Review Questions

    • Identify peptide and steroid hormones based on their properties and roles in the body.
    • Understand the mechanisms of GPCR activation and the roles of G proteins and adenylate cyclase in cellular signaling.

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    Description

    Test your knowledge on receptor pathways in endocrinology. This quiz covers hormone interactions and the role of G proteins in signaling. Enhance your understanding of how peptide hormones function in the body.

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