Passage Across Membranes: Cell Transport and Barriers
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Questions and Answers

What is the half-life of the radioactive isotope 137Cs, which is similar to potassium in its behavior?

  • 30 years (correct)
  • 50 years
  • 15 years
  • 100 years

    • Compared to the Chernobyl disaster, what is the order of magnitude of the releases of iodine-131 and caesium-137 from Fukushima?

  • One-tenth
  • Ten times
  • The same (correct)
  • One hundred times

    • What is the primary factor that affects the absorption of substances in the gastrointestinal tract?

  • pH
  • Motility and mixing in the GI tract
  • Lipid solubility (correct)
  • Disintegration of dosage form

    • What is the main reason for the rapid absorption of gases, vapors, and volatile liquids in the lungs?

    <p>All of the above</p> Signup and view all the answers

    What must substances cross to reach blood vessels in the skin?

    <p>Several cell layers</p> Signup and view all the answers

    What is the minimum distance from the Fukushima plant where radioactive caesium levels have been reported to be high enough to cause concern?

    <p>30 km</p> Signup and view all the answers

    What is the primary factor that determines the rate of passive diffusion across a cell membrane?

    <p>Surface area of the membrane</p> Signup and view all the answers

    What is the characteristic of a chemical that allows it to diffuse through the lipid bilayer of a cell membrane?

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

    Which type of transport is characterized by the movement of molecules along a concentration gradient without the use of energy?

    <p>Passive transport</p> Signup and view all the answers

    What is the minimum molecular size required for a molecule to move through cell pores?

    <p>0.4 nm</p> Signup and view all the answers

    What is the characteristic of a molecule that is a substrate for facilitated transport?

    <p>Specific binding to a carrier protein</p> Signup and view all the answers

    What is the primary difference between active transport and facilitated transport?

    <p>Energy requirement</p> Signup and view all the answers

    Which of the following xenobiotics is sequestered in adipose tissue as depot stores?

    <p>Organochlorine compounds</p> Signup and view all the answers

    What is the primary target tissue for blood lead toxicity?

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

    What is the mechanism by which lead is sequestered in growing bone?

    <p>Through deposition in hydroxyapatite</p> Signup and view all the answers

    What is the effect of pregnancy and breast feeding on sequestered organochlorine compounds?

    <p>Depot mobilization into blood</p> Signup and view all the answers

    Which of the following xenobiotics produces effects on the nervous tissue?

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

    What is the primary factor affecting absorption through endothelial pores into the circulation?

    <p>Blood flow</p> Signup and view all the answers

    What is the common characteristic of xenobiotics that produce effects on specific body tissues or organs?

    <p>They must be bioavailable to distribute from blood to target tissue</p> Signup and view all the answers

    What is the bioavailability of a drug administered intravenously?

    <p>100%</p> Signup and view all the answers

    Which of the following routes of exposure has the largest surface area?

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

    What is the primary reason for the low bioavailability of lidocaine?

    <p>All of the above</p> Signup and view all the answers

    What is the main purpose of understanding the extent of absorption and bioavailability?

    <p>To determine the toxic effects of a drug</p> Signup and view all the answers

    What is the term for the process by which a drug is destroyed in the gut and liver before reaching the systemic circulation?

    <p>First Pass Effect</p> Signup and view all the answers

    What is the primary mechanism for the excretion of water-soluble toxicants from the body?

    <p>Passive transport through the kidney</p> Signup and view all the answers

    What is the function of the liver in the elimination of toxicants?

    <p>To metabolize lipid-soluble toxicants to more water-soluble forms</p> Signup and view all the answers

    Which of the following is NOT a major route of elimination for toxicants?

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

    What is the term for the process by which lipid-soluble toxicants are reabsorbed into the bloodstream?

    <p>Systemic toxicity</p> Signup and view all the answers

    Which of the following is an example of active transport in the elimination of toxicants?

    <p>Biliary secretion</p> Signup and view all the answers

    Why is mother's milk an important route of elimination for toxicants?

    <p>It allows for the transfer of toxicants from the mother to the baby</p> Signup and view all the answers

    What is the primary mechanism for the excretion of gases and volatile liquids from the body?

    <p>Diffusion through the lung</p> Signup and view all the answers

    What is the significance of the molecular weight of a toxicant in determining its route of elimination?

    <p>Water-soluble toxicants have a molecular weight of &lt; 70,000</p> Signup and view all the answers

    Which of the following is a minor route of elimination for toxicants?

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

    What is the term for the process by which toxicants are changed from lipid-soluble to more water-soluble forms?

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

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