GATE BT 2026 • Q16
MCQ • 1 Mark
Section 2: General Biotechnology
Cell structure and signaling
Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Which of the following enzyme is involved in the protection of cells from reactive
oxygen species?
Options:
-
(A) Hexokinase
-
(B) Glucose 6-phosphate dehydrogenase
-
(C) Enolase
-
(D) Pyruvate kinase
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.16)**
**1. Governing Concept**:
- **Topic**: Cell Biology & Antioxidant Defense Mechanisms (ROS Scavenging)
- Reactive oxygen species (ROS) such as superoxide radicals ($\text{O}_2^{\bullet-}$), hydrogen peroxide ($\text{H}_2\text{O}_2$), and hydroxyl radicals ($\text{OH}^\bullet$) cause severe oxidative damage to DNA, lipids, and proteins.
- **Superoxide Dismutase (SOD)** catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide:
$2\text{O}_2^{\bullet-} + 2\text{H}^+ \xrightarrow{\text{SOD}} \text{O}_2 + \text{H}_2\text{O}_2$
- Hydrogen peroxide is subsequently decomposed to water and oxygen by **Catalase** or **Glutathione Peroxidase**.
**2. Option Analysis**:
- **Option (A) [DNA Polymerase] is INCORRECT**: Replicates DNA; does not scavenge free radicals.
- **Option (B) [Superoxide dismutase] is CORRECT**: The primary antioxidant enzyme scavenging superoxide anions to protect cells from oxidative stress.
- **Option (C) [Hexokinase] is INCORRECT**: Glycolytic enzyme phosphorylating glucose to glucose-6-phosphate.
- **Option (D) [Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO)] is INCORRECT**: Photosynthetic carbon fixation enzyme in the Calvin cycle.
**3. Final Answer**:
- **Correct Choice**: **B**
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