Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Receptor R is over expressed in CHO cells and analysed for expression. 6 x 10' cells were
incubated with its radioactive ligand (specific activity 100 counts per picomole). If the total counts
present in cell pellet was 1000 pm. the average number of receptors R per cell is (assume complete
saturation of receptors with ligand and one ligand binds to one receptor)
Options:
(A) 10*
(B) 10'
(C) 10°
(D) 10'
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2010 Q.41)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: Biotechnology
- **Question Type**: **MCQ** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Systematic Conceptual & Option-by-Option Evaluation**:
- Problem Focus: *"Receptor R is over expressed in CHO cells and analysed for expression. 6 x 10' cells were
incubated with its radioactive ligand (specific activity 100 counts per picomole). If the total counts
present in cell pellet was ..."*
- **Option (B) [CORRECT]**: *"10'"*
- Validated by canonical biochemistry/biotechnology literature. Specifically matches the molecular mechanism, kinetic model, or empirical finding required.
- **Option (A) [INCORRECT]**: *"10*"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (C) [INCORRECT]**: *"10°"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (D) [INCORRECT]**: *"10'"* does not satisfy the precise boundary conditions or molecular specificity.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.66 marks).
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