15 high-quality UPSC Prelims-style questions based on the bioelectronic sensors and genetically engineered bacteria research, complete with explanations:
Section A: Basic Concepts
Q1. What is the primary advantage of using whole-cell biosensors over traditional enzyme-based biosensors?
(a) They are always smaller in size
(b) They can self-repair and maintain functionality
(c) They don't require any power source
(d) They provide instant results
Answer: (b) They can self-repair and maintain functionality
Explanation: Whole-cell biosensors use living microorganisms that can maintain and repair themselves, unlike fragile enzyme-based sensors.
Q2. The recent breakthrough in bioelectronic sensors by Imperial College London and Zhejiang University primarily involves:
(a) Using bacteria to generate electricity
(b) Integrating bacterial sensors with electronic systems
(c) Creating bacterial computers
(d) Developing new antibiotics
Answer: (b) Integrating bacterial sensors with electronic systems
Explanation: The study demonstrated how genetically engineered bacteria can interface directly with electronics to create self-powered chemical sensors.
Section B: Technical Details
Q3. Which bacteria was used as the platform for developing these bioelectronic sensors?
(a) Salmonella
(b) Escherichia coli
(c) Bacillus subtilis
(d) Pseudomonas
Answer: (b) Escherichia coli
Explanation: The researchers used genetically engineered E. coli bacteria as 'containers' for their biosensor modules.
Q4. What was the function of phenazines in this biosensor system?
(a) To provide nutrients to the bacteria
(b) To generate measurable electrical signals
(c) To kill harmful pathogens
(d) To change the color of the solution
Answer: (b) To generate measurable electrical signals
Explanation: Phenazines are nitrogen-containing organic molecules that produce current when measured using voltammetry.
Section C: Applications
Q5. Which of the following substances were these biosensors able to detect?
Arabinose
Mercury ions
Oxygen levels
Carbon dioxide
Select the correct answer using the code below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1, 3 and 4 only
(d) 1, 2, 3 and 4
Answer: (a) 1 and 2 only
Explanation: The study specifically demonstrated detection of arabinose (a sugar) and mercury ions.
Q6. The biosensor could detect mercury concentrations:
(a) Above WHO safety limits
(b) Equal to WHO safety limits
(c) Below WHO safety limits
(d) Only in highly concentrated solutions
Answer: (c) Below WHO safety limits
Explanation: The sensor detected just 25 nanomoles of mercury, which is below the WHO safety limit.
Section D: Scientific Principles
Q7. The 'AND' logic gate implemented in this system means:
(a) Bacteria would glow when exposed to light
(b) Signal was produced only when two specific molecules were present
(c) Bacteria could survive in both air and water
(d) The sensor could work both day and night
Answer: (b) Signal was produced only when two specific molecules were present
Explanation: An 'AND' gate ensures output only when both required inputs are present.
Q8. What electrochemical technique was used to measure the bacterial output?
(a) Chromatography
(b) Voltammetry
(c) Electrophoresis
(d) Spectrophotometry
Answer: (b) Voltammetry
Explanation: The study used voltammetry to measure the phenazines produced by the bacteria.
Section E: Comparative Analysis
Q9. Compared to optical biosensors, the main advantage of this new bioelectronic system is:
(a) It's more colorful
(b) It's easier to integrate with portable electronics
(c) It works without any bacteria
(d) It's more expensive to produce
Answer: (b) It's easier to integrate with portable electronics
Explanation: Optical signals are harder to integrate with electronics than the electrical signals this system produces.
Section F: Environmental Relevance
Q10. These biosensors would be particularly useful for:
Monitoring water pollution
Detecting food contaminants
Measuring atmospheric pressure
Soil fertility testing
Select the correct answer using the code below:
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1, 2 and 4 only
(d) 1, 3 and 4 only
Answer: (a) 1 and 2 only
Explanation: The study demonstrated applications in detecting water contaminants (mercury) and could be adapted for food safety.
Section G: Time Factors
Q11. How long did it take for the arabinose sensor to produce a detectable signal?
(a) 30 minutes
(b) 1 hour
(c) 2 hours
(d) 24 hours
Answer: (c) 2 hours
Explanation: The arabinose detection system produced signals in approximately two hours.
Section H: Future Potential
Q12. The modular design of these biosensors means they:
(a) Can only detect one specific substance
(b) Can be reprogrammed to detect different chemicals
(c) Must be used in laboratory settings only
(d) Require daily calibration
Answer: (b) Can be reprogrammed to detect different chemicals
Explanation: The modular nature allows for adaptation to detect various target compounds.
Section I: Indian Context
Q13. Such biosensors could help India with:
(a) Space exploration only
(b) Only medical diagnostics
(c) Monitoring pollution in rivers like Ganga
(d) Increasing crop yields directly
Answer: (c) Monitoring pollution in rivers like Ganga
Explanation: They could detect heavy metals and other pollutants in water bodies.
Section J: Safety Aspects
Q14. The mercury detection system used which protein to bind mercury ions?
(a) Hemoglobin
(b) MerR
(c) Insulin
(d) Collagen
Answer: (b) MerR
Explanation: The MerR protein specifically binds mercury ions in this system.
Section K: Signal Amplification
Q15. Why was a genetic amplifier added to the mercury detection system?
(a) To make the bacteria grow faster
(b) To increase the electrical signal from trace amounts
(c) To change the color of the output
(d) To prevent bacterial death
Answer: (b) To increase the electrical signal from trace amounts
Explanation: The amplifier boosted phenazine production to detect very low mercury concentrations.
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