Determine the correctness of otherwise of the following Assertion [a] and the Reason [r]
Assertion [a]: It is possible to regenerate a whole plant from a single plant cell.
Reason [r]: It is easier to introduce transgenes in to plants than animals.
Options:
(B) Both [a] and [r] are true but [r] is not the correct reason for [a]
(A) Both La, and [r] are true and [r] is the correct reason for Lal
(C) Both [a| and [r] are false
(D) [a] is true but [r] is false
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.54)**
**1. Governing Concept**:
- **Topic**: Cell Biology & Active Transport vs. Facilitated Diffusion
- Comparison of carrier-mediated membrane transport modes:
- **Facilitated diffusion**: Passive transport down electrochemical/concentration gradient ($\Delta \mu < 0$); does not require metabolic energy; saturable carrier kinetics.
- **Active transport**: Transports solutes against electrochemical gradient ($\Delta \mu > 0$); strictly requires energy input (ATP hydrolysis in primary active transport, or co-transport of coupled ions in secondary active transport).
- Both modes exhibit saturation kinetics ($V_{\max}, K_m$) and competitive inhibition.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Falsely claims facilitated diffusion consumes ATP.
- **Option (B) is CORRECT**: Formally differentiates active transport (energy-dependent, against gradient) from facilitated diffusion (passive, down gradient, saturable).
- **Option (C) is INCORRECT**: Facilitated diffusion is saturable.
- **Option (D) is INCORRECT**: Disputed transport statements.
**3. Final Answer**:
- **Correct Choice**: **B**
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