Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
The minimum value of the function
f(x) = x + 4
x
for x > 0 is
Options:
(A) 1
(B) 2
(C) 3
(D) 4
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.14)**
**1. Governing Concept**:
- **Topic**: Microbiology & Bacterial Endospore Resistance
- Bacterial endospores (formed by *Bacillus* and *Clostridium*) exhibit extreme resistance to heat, radiation, desiccation, and chemical disinfectants due to:
1. **Dehydrated core**: Water content is only 10–25%.
2. **Calcium dipicolinate (dipicolinic acid complexed with $\text{Ca}^{2+}$)**: Constitutes ~10% of spore dry weight, intercalating into DNA and stabilizing proteins against thermal denaturation.
3. **Small Acid-Soluble Spore Proteins (SASPs)**: Bind and saturate spore DNA, converting it from B-form to A-form, protecting it from UV radiation and heat.
4. **Multi-layered protective proteinaceous coat and thick cortex**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Spores have extremely low water content (dehydrated), not high.
- **Option (B) is CORRECT**: High concentration of calcium dipicolinate and SASPs in the core confers extraordinary thermal resistance.
- **Option (C) is INCORRECT**: Spores are metabolically dormant, not hyperactive.
- **Option (D) is INCORRECT**: Spore coat is composed of dense cross-linked proteins, not thin lipids.
**3. Final Answer**:
- **Correct Choice**: **B**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.