Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
If a denatured protein of human origin is injected into a rabbit, antibodies generated
will recognize the ________ structure of the protein.
Options:
(A) primary
(B) secondary
(C) tertiary
(D) quaternary
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2024 Q.26)**
**1. Governing Concept**:
- **Topic**: Immunology & Epitope Recognition
- Thermal or chemical denaturation of a protein unfolds its tertiary and quaternary native conformation, breaking non-covalent interactions and exposing the linear, continuous amino acid sequence.
- Antibodies elicited against fully denatured antigens are directed primarily against linear, continuous epitopes, which reflect the **primary structure**. Antibodies against native proteins typically recognize conformational (discontinuous) epitopes formed by tertiary/quaternary folding.
**2. Option Analysis**:
- **Option (A) [primary] is CORRECT**: Denatured protein presents linear sequence epitopes reflecting the primary covalent polypeptide chain.
- **Option (B) [secondary] is INCORRECT**: Secondary structural elements ($\alpha$-helices, $\beta$-sheets) are extensively disrupted upon complete denaturation.
- **Option (C) [tertiary] is INCORRECT**: Tertiary native 3D fold is destroyed during denaturation.
- **Option (D) [quaternary] is INCORRECT**: Subunit assembly is dissociated upon denaturation.
**3. Final Answer**:
- **Correct Choice**: **A**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.