Biotransformation and Excretion of Toxicants
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Questions and Answers

What is the primary purpose of biotransformation in the body?

  • To maintain the lipophilic nature of xenobiotics
  • To change toxic molecules into more water-soluble forms (correct)
  • To increase the toxicity of the xenobiotics
  • To decrease the hydrophilicity of toxicants

    • How do biotransformed metabolites differ from the original toxicant molecules?

  • They are chemically identical to the original toxicant
  • They are less hydrophilic than the original toxicant
  • They are chemically distinct from the original toxicant (correct)
  • They have reduced water solubility compared to the original toxicant

    • What is a key benefit of the hydrophilic nature of biotransformed metabolites?

  • It facilitates their elimination from the body (correct)
  • It increases their retention in the body tissues
  • It enhances their ability to penetrate lipid membranes
  • It reduces their ability to cross membranes

    • Which phase of xenobiotic metabolism introduces a polar group into the molecule?

    <p>Phase I</p> Signup and view all the answers

    What is the main effect of introducing a polar group in phase I of xenobiotic metabolism?

    <p>Enhance water solubility of the xenobiotic</p> Signup and view all the answers

    How does reducing reabsorption of metabolites by organs of elimination contribute to detoxification?

    <p>It ensures that the toxicants are effectively eliminated from the body</p> Signup and view all the answers

    What is the primary purpose of phase II reactions in biotransformation?

    <p>To produce a water-soluble conjugation product</p> Signup and view all the answers

    Where do microsomal enzymes, which are involved in phase I reactions, primarily occur?

    <p>Bound to the membrane of the endoplasmic reticulum</p> Signup and view all the answers

    Which enzyme system is most important in catalyzing phase I biotransformation reactions?

    <p>Cytochrome P-450</p> Signup and view all the answers

    What is the main process that occurs during phase I biotransformation reactions?

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

    Which organ has the highest capacity for biotransformation?

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

    What is the primary outcome of phase II reactions in biotransformation?

    <p>Detoxification of toxicants</p> Signup and view all the answers

    Which group enhances the solubility of a toxicant in water during phase I biotransformation reactions?

    <p>'Unmasking' group</p> Signup and view all the answers

    Which cells are primarily involved in glucuronidation during phase II reactions?

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

    What is the primary role of cytochrome P-450 in phase I biotransformation reactions?

    <p>Catalyzing oxidation of toxicants</p> Signup and view all the answers

    Which body parts have a low capacity for biotransformation?

    <p>Skin, testes, placenta</p> Signup and view all the answers

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