Question:medium
All of the following are involved in generating free oxygen radicals for the killing of bacteria except:
All of the following are involved in generating free oxygen radicals for the killing of bacteria except:
Show Hint
Find the antioxidant enzyme that mops up peroxide rather than making radicals.
Updated On: Jun 24, 2026
- Superoxide dismutase
- Fenton reaction
- NADPH oxidase
- Glutathione peroxidase
Show Solution
The Correct Option is D
Solution and Explanation
The microbicidal oxygen-dependent system of phagocytes depends on a chain that manufactures progressively more toxic radicals. The chain opens with NADPH oxidase, the membrane enzyme that reduces $O_2$ to the superoxide radical $O_2^-$; this enzyme defect underlies chronic granulomatous disease. Superoxide dismutase then dismutates two superoxide molecules into $H_2O_2$, and the Fenton reaction (iron-catalysed) turns that peroxide into the hydroxyl radical, the most bactericidal species. Each of these three steps either makes or transforms a free radical, so all are part of radical generation. Glutathione peroxidase, by contrast, belongs to the cellular defence arm: it scavenges peroxide by oxidising glutathione, neutralising ROS so they do not damage host tissue. Because it terminates rather than creates radicals, it is the odd one out.
\[\boxed{\text{Glutathione peroxidase}}\]
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