Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
Correctly match the Inhibitor with its respective Function in mitochondrial
respiration.
Inhibitor Function
P. FCCP 1. Inhibits cytochrome c oxidase
Q. Cyanide 2. Makes the membrane permeable to protons
R. Oligomycin A 3. Blocks mitochondrial uptake of succinate
S. Butyl malonate 4. Inhibits ATP synthase
Options:
(A) P-2; Q-1; R-4; S-3
(B) P-2; Q-3; R-1; S-4
(C) P-2; Q-4; R-3; S-1
(D) P-3; Q-1; R-2; S-4
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.37)**
**1. Governing Concept**:
- **Topic**: Molecular Genetics & Ames Test for Mutagenicity
- The **Ames test** assesses the mutagenic/carcinogenic potential of chemical compounds:
- Uses mutant strains of ***Salmonella enterica* serovar Typhimurium** that carry point mutations in the histidine biosynthesis operon ($his^-$ auxotrophs), making them unable to grow on histidine-deficient media.
- A suspected mutagen induces **reversion mutations ($his^- \to his^+$)**, restoring the wild-type ability to synthesize histidine and form visible colonies on minimal agar.
- Rat liver homogenate (**S9 fraction**) is added to simulate mammalian metabolic activation by cytochrome P450 enzymes.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: The Ames test uses *Salmonella enterica* Typhimurium, not *E. coli*.
- **Option (B) is CORRECT**: Specifically measures the frequency of back-mutation / reversion of histidine auxotrophy ($his^-$) to prototrophy ($his^+$).
- **Option (C) is INCORRECT**: The assay measures bacterial mutation reversion, not viral plaque formation.
- **Option (D) is INCORRECT**: S9 fraction provides metabolic activation, not antibiotic selection.
**3. Final Answer**:
- **Correct Choice**: **B**
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