[Campbell Biology P.153] A patient has been taking a certain sedative for an extended period... | Practice Question

A patient has been taking a certain sedative for an extended period and now requires a higher dose to achieve the same effect. Which cellular organelle is primarily involved in this phenomenon, and what is the underlying molecular mechanism?

  • A: Rough ER; it proliferates to increase protein synthesis for drug breakdown.
  • B: Golgi apparatus; it modifies and packages the drug for excretion.
  • C: Smooth ER; its enzymes add hydroxyl groups to drug molecules, making them more water-soluble, and chronic drug use leads to proliferation of smooth ER and its associated detoxification enzymes.
  • D: Lysosomes; they contain hydrolytic enzymes that break down the drug, and their activity increases with prolonged drug exposure.

Explanation

The text explicitly states that 'Other enzymes of the smooth ER help detoxify drugs and poisons, especially in liver cells. Detoxification usually involves adding hydroxyl groups to drug molecules, making them more water-soluble and easier to flush from the body.' It also mentions that 'barbiturates, alcohol, and many other drugs induce the proliferation of smooth ER and its associated detoxification enzymes, thus increasing the rate of detoxification. This, in turn, increases tolerance to the drugs, meaning that higher doses are required to achieve a particular effect, such as sedation.' This directly explains the phenomenon of drug tolerance.