20. Which of the following is not a phase one reaction ?

  A) oxidation
 B) reduction
 C)hydrolysis
 D) conjugation

Answer Conjugation

Refernce-Harper28th

XENOBIOTICS 

In phase 1, the major reaction involvedis hydroxylation, catalyzed mainly by members of a class of enzymes referred to as monooxygenases orcytochrome P450s. Hydroxylation may terminate the action of a drug, though this is not always the case. Inaddition to hydroxylation, these enzymes catalyze a wide range of reactions, including those involvingdeamination, dehalogenation, desulfuration, epoxidation, peroxygenation, and reduction. Reactions involvinghydrolysis (eg, catalyzed by esterases) and certain other non-P450-catalyzed reactions also occur in phase 1.

In phase 2, the hydroxylated or other compounds produced in phase 1 are converted by specific enzymes tovarious polar metabolites by conjugation with glucuronic acid, sulfate, acetate, glutathione, or certain aminoacids, or by methylation