Certified in Public Health (CPH) Practice Exam

What is primarily involved in Phase 2 metabolism of chemicals?

1. Microsomal enzymes

2. Decrease in the polarity of a chemical

3. Increase in the toxicity of a chemical

4. Addition of an endogenous moiety

The correct answer is: Addition of an endogenous moiety

Phase 2 metabolism, also known as conjugation, primarily involves the addition of an endogenous moiety to a chemical compound. This process typically leads to the formation of a more water-soluble compound, which enhances the ability of the body to excrete the substance, often through urine or bile. This conjugation typically utilizes various enzymes, including transferases, that facilitate the reaction between the endogenous molecules, such as glucuronic acid, sulfate, or glutathione, and the target chemical. The addition of these endogenous moieties serves to neutralize potentially harmful chemical properties and often results in a compound that is less toxic than the original. This transformation reduces the overall biological activity of the substance, facilitating its elimination from the body and minimizing potential toxicity. In contrast, the other choices are associated with different aspects of metabolism or do not accurately reflect Phase 2 metabolism's purpose and mechanism. Thus, understanding the role of endogenous moieties in Phase 2 metabolism is essential for comprehending how the body detoxifies various substances.