Fed batch cultivation is suitable for which of the following?
P. Processes with substrate inhibition
Q. Processes with product inhibition
R. High cell density cultivation
(A) P and Q only (B) P and R only (C) Q and R only (D) P, Q and R
Options:
(A) P and Q only
(B) P and R only
(C) Q and R only
(D) P, Q and R
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.17)**
**1. Governing Concept & Question Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Topic**: Biochemistry / Bioenergetics (Chemiosmotic Hypothesis & ATP Synthase Topology)
**2. Detailed Step-by-Step Analysis**:
- According to Peter Mitchell's **Chemiosmotic Theory**:
1. The electron transport chain (Complexes I, III, and IV) actively pumps protons ($H^+$) from the **mitochondrial matrix** across the inner mitochondrial membrane into the **intermembrane space**.
2. This generates a proton motive force ($\Delta p$) characterized by a higher proton concentration (lower pH, positive charge) in the intermembrane space and a lower proton concentration (higher pH, negative charge) in the matrix.
3. The $F_o F_1$-ATP synthase complex is embedded in the inner mitochondrial membrane:
- The hydrophobic $F_o$ proton channel spans the inner membrane.
- The catalytic $F_1$ headpiece ($\alpha_3\beta_3$ hexamer) projects into the **mitochondrial matrix**.
4. Protons flow down their electrochemical gradient from the **intermembrane space into the matrix** through $F_o$, driving mechanical rotation of the $\gamma$ stalk, which synthesizes ATP from ADP and $P_i$ on the $F_1$ catalytic sites in the **mitochondrial matrix**.
- Therefore, $F_1$ is located in the **mitochondrial matrix**.
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: $F_1$ is not on the outer membrane.
- **Option (B) [CORRECT]**: The catalytic $F_1$ subunit of ATP synthase faces and resides within the mitochondrial matrix.
- **Option (C) [INCORRECT]**: The intermembrane space contains the $H^+$ reservoir, but $F_1$ extends into the matrix.
- **Option (D) [INCORRECT]**: $F_1$ does not project into the cytoplasm.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: +1.0 Mark (Negative marking: -0.33 marks).
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