Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
Which of the following statements are CORRECT about the function of fetal bovine serum
in animal cell culture?
P. It stimulates cell growth
Q. It enhances cell attachment
S.
R. It provides hormones and minerals
It maintains pH at 7.4
Options:
(A) P and Q only
(B) P and S only
(C) P, Q and R only
(D) P, Q, R and S
10 ---
GATE 2019
Biotechnology
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.45)**
**1. Governing Concept**:
- **Topic**: Enzyme Kinetics & Allosteric Cooperativity (Hill Equation)
- For an allosteric enzyme exhibiting cooperative substrate binding:
- Described by the **Hill equation**:
$\theta = \frac{[S]^n}{K_{0.5}^n + [S]^n}$
- $n = 1$: Non-cooperative, standard hyperbolic Michaelis-Menten kinetics.
- $n > 1$: **Positive cooperativity**, characterized by a **sigmoidal (S-shaped)** velocity vs. substrate curve. Binding of the first substrate molecule increases the affinity of remaining vacant active sites on the multimeric complex.
- $n < 1$: Negative cooperativity.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Claims hyperbolic kinetics for cooperative enzymes.
- **Option (B) is INCORRECT**: Claims $n = 1$ indicates positive cooperativity.
- **Option (C) is CORRECT**: Confirms that positive cooperativity yields sigmoidal saturation kinetics with Hill coefficient $n > 1$.
- **Option (D) is INCORRECT**: Mischaracterizes allosteric effector mechanisms.
**3. Final Answer**:
- **Correct Choice**: **C**
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