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Chapter 5. Absorption, Distribution, and Excretion of Toxicants

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

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

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

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

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

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

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

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

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

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

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

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

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

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

b. increased biotransformation of the toxin by gastrointestinal cells.

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

d. increased dilution of the toxin dose.

e. increased intestinal motility.

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

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

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

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

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

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

Which of the following is ...

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