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Chapter 5. Absorption, Distribution, and Excretion of Toxicants

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Biotransformation is vital in removing toxins from the circulation. All of the following statements regarding biotransformation are true EXCEPT:

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a. Many toxins must be biotransformed into a more lipid-soluble form before they can be excreted from the body.

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b. The liver is the most active organ in the biotransformation of toxins.

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c. Water solubility is required in order for many toxins to be excreted by the kidney.

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d. The kidney plays a major role in eliminating toxicants from the body.

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e. The lungs play a minor role in ridding the body of certain types of toxins.

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Which of the following statements about active transport across cell membranes is FALSE?

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a. Unlike simple or facilitated diffusion, active transport pumps chemicals against an electrochemical or concentration gradient.

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b. Unlike simple diffusion, there is a rate at which active transport becomes saturated and cannot move chemicals any faster.

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c. Active transport requires the expenditure of ATP in order to move chemicals against electrochemical or concentration gradients.

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d. Active transport exhibits a high level of specificity for the compounds that are being moved.

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e. Metabolic inhibitors do not affect the ability to perform active transport.

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Which of the following might increase the toxicity of a toxin administered orally?

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a. increased activity of the mdr transporter (p-glycoprotein).

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b. increased biotransformation of the toxin by gastrointestinal cells.

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c. increased excretion of the toxin by the liver into bile.

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d. increased dilution of the toxin dose.

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e. increased intestinal motility.

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Which of the following most correctly describes the first-pass effect?

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a. The body is most sensitive to a toxin the first time that it passes through the circulation.

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b. Orally administered toxins are partially removed by the GI tract before they reach the systemic circulation.

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c. It only results from increased absorption of toxin by GI cells.

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d. It is often referred to as “postsystemic elimination.”

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e. A majority of the toxin is excreted after the first time the blood is filtered by the kidneys.

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Which of the following is ...

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