AIPPG 2003 Dental MCQ Answer 09

The Correct Answer is A

The body is exposed to a wide variety of foreign compounds, called xenobiotics. Exposure to some such compounds is unintentional (e.g., environmental or food substances), while others are deliberately used as drugs.

Most enzymes involved in drug metabolism are located within the lipophilic membranes of the smooth endoplasmic reticulum (SER). When the SER is isolated in the laboratory by tissue homogenation and centrifugation, the SER membranes re-form into vesicles called microsomes. Since most of the enzymes carry out oxidation reactions, this SER complex is referred to as the microsomal mixed function oxidase (MFO) system.

An interesting and important feature of the cytochrome P450 mixed function oxidase system is the ability of some xenobiotics to induce the synthesis of new enzyme. Microsomal enzyme induction is a complex and poorly understood process associated with an increase in liver weight, proliferation of the SER, and synthesis of P₄₅₀ enzymes.

NADPH cytochrome P-450-reductase.is involved, but not in activation of Xenobiotics .