Before You Begin
Question #45146
The Question
A researcher uses a sandwich ELISA to detect a specific bacterial antigen in a water sample taken from an industrial effluent site known for severe heavy metal pollution. Despite a confirmed high bacterial load in the sample, the ELISA yields a false-negative result (no color development). Assuming all washing steps and antigen-antibody bindings occurred optimally, which of the following best explains this anomaly based on enzyme kinetics?
Options
- A.
Heavy metals acted as competitive inhibitors to the reporter enzyme, a condition that could not be reversed because the antigen concentration was too high.
- B.
Heavy metals acted as non-competitive inhibitors, binding to the reporter enzyme and decreasing its Vmax without altering its Km for the chromogenic substrate.
- C.
The pollutants denatured the bacterial DNA, preventing the reporter enzyme from initiating the amplification required for color development.
- D.
The heavy metals bound to the active site of the reporter enzyme, permanently altering its Km and preventing the initial antigen-antibody complex formation.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
ELISA|Nutrient Immobility|Enzyme-Substrate kinetics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question integrates Class 12 Biotechnology (ELISA principles) with Class 11 Biomolecules (Enzyme inhibition kinetics).
The common misconception is treating ELISA as a magic 'color-producing' black box, forgetting that the final step is a standard biochemical enzyme-substrate reaction.
Students must recognize that environmental pollutants (heavy metals) can induce a false negative by acting as non-competitive inhibitors, which specifically lower Vmax without altering Km.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology and Its Applications - Class 12 |
| Concept | Molecular Diagnosis by ELISA |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |