Xenobiotics & Detoxication (CYP450) MCQ Quiz | Environmental & Cancer

Welcome to our specialized quiz on Xenobiotics and Detoxication, a critical topic in Environmental & Cancer studies for MBBS students. This quiz is designed to test your understanding of how the human body processes and eliminates foreign compounds, with a special focus on the Cytochrome P450 (CYP450) enzyme system. You will encounter 25 multiple-choice questions covering Phase I and Phase II reactions, enzyme induction and inhibition, genetic polymorphisms, and their clinical implications in toxicology and carcinogenesis. Challenge your knowledge and solidify your concepts. After submitting your answers, you can review your score and see detailed corrections. For your future reference, a downloadable PDF of all questions and their correct answers is also available.

1. Which phase of xenobiotic metabolism primarily involves oxidation, reduction, and hydrolysis reactions?

2. The Cytochrome P450 enzyme system is predominantly located in which subcellular organelle?

3. Which of the following is a classic example of a Phase II conjugation reaction?

4. Grapefruit juice is a well-known inhibitor of which specific CYP450 enzyme, leading to numerous drug interactions?

5. The conversion of the pro-carcinogen benzo[a]pyrene (from tobacco smoke) to a highly reactive carcinogenic epoxide is mediated by:

6. Paracetamol (acetaminophen) overdose leads to hepatotoxicity due to the depletion of which endogenous substrate?

7. Genetic polymorphism in which of the following enzymes is responsible for the “poor metabolizer” phenotype for drugs like codeine?

8. Which of the following statements about Phase I metabolism is generally TRUE?

9. The primary purpose of Phase II detoxification is to:

10. A patient on warfarin who starts taking rifampicin may experience a decreased anticoagulant effect. This is most likely due to:

11. Which enzyme family is the most abundant and catalytically active for drug metabolism in the human liver?

12. Glutathione-S-transferase (GST) plays a crucial role in detoxifying electrophilic compounds by conjugating them with:

13. The “first-pass effect” primarily refers to xenobiotic metabolism occurring in the:

14. What is the role of NADPH-cytochrome P450 reductase?

15. A patient who is a “rapid metabolizer” due to a CYP2D6 gene duplication would likely require what adjustment for a drug that is an active CYP2D6 substrate?

16. In the context of toxicology, “lethal synthesis” refers to:

17. Which of the following is NOT a Phase II metabolic pathway?

18. Aflatoxin B1, a mycotoxin, is converted to a potent carcinogen by which enzyme system?

19. The family of transporter proteins responsible for effluxing xenobiotics and their metabolites out of cells, contributing to multidrug resistance, is known as:

20. Smoking cigarettes can decrease the efficacy of drugs like theophylline. This is an example of:

21. The main metallic cofactor present in the active site of all cytochrome P450 enzymes is:

22. UDP-glucuronosyltransferase (UGT) enzymes are critical for the metabolism and excretion of which endogenous compound?

23. A patient with Gilbert’s syndrome has a reduced capacity for which type of conjugation reaction?

24. The highly toxic metabolite of paracetamol, N-acetyl-p-benzoquinone imine (NAPQI), is normally detoxified by:

25. Which phase of metabolism is often deficient or underdeveloped in neonates, leading to conditions like “gray baby syndrome” with chloramphenicol?