Biological recognition elements in biosensors MCQs With Answer

Biological recognition elements in biosensors MCQs With Answer

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Introduction

This quiz set on Biological recognition elements in biosensors is designed for M.Pharm students to deepen understanding of the molecular components that confer selectivity and sensitivity in biosensing platforms. It covers enzymes, antibodies, nucleic acids (including aptamers), receptors, cells, molecularly imprinted polymers and peptides, plus critical topics such as immobilization chemistries, orientation, kinetics (affinity and specificity), stability, regeneration and practical implications for pharmaceutical analysis and therapeutic monitoring. Questions focus on conceptual clarity, practical design choices and common challenges in deploying recognition elements in real-world biosensors used in drug development, quality control and point-of-care diagnostics.

Q1. Which of the following best defines a biological recognition element in a biosensor?

  • A transducer that converts a biological interaction into an electrical signal
  • A biological molecule or construct that selectively binds or reacts with the target analyte
  • A software algorithm used to interpret sensor output
  • An external reference electrode used for calibration

Correct Answer: A biological molecule or construct that selectively binds or reacts with the target analyte

Q2. Which recognition element is most appropriate for highly specific detection of a small drug molecule where antibody generation is difficult?

  • Whole cell receptors
  • Enzymes
  • Aptamers selected by SELEX
  • Lectins

Correct Answer: Aptamers selected by SELEX

Q3. Which immobilization chemistry commonly provides covalent attachment of proteins to carboxyl-functionalized sensor surfaces?

  • EDC/NHS coupling
  • Physical adsorption
  • Biotin–streptavidin noncovalent binding
  • Hydrophobic interactions

Correct Answer: EDC/NHS coupling

Q4. Which characteristic of an antibody influences the sensor’s affinity to the target analyte most directly?

  • Isotype (IgG vs IgM)
  • Paratope complementarity and binding site conformation
  • Fc glycosylation pattern
  • Heavy chain subclass

Correct Answer: Paratope complementarity and binding site conformation

Q5. Which recognition element is inherently catalytic and can be used to amplify signal by substrate turnover?

  • Antibodies
  • Enzymes
  • Aptamers
  • Molecularly imprinted polymers

Correct Answer: Enzymes

Q6. What is the principal advantage of using molecularly imprinted polymers (MIPs) as recognition elements?

  • Unlimited selectivity for any protein epitope
  • High thermal and chemical stability compared to biological receptors
  • Intrinsic enzymatic activity
  • Ease of generating folding-specific tertiary structures

Correct Answer: High thermal and chemical stability compared to biological receptors

Q7. Which factor most directly affects the limit of detection (LOD) provided by a recognition element?

  • Thickness of the transducer substrate
  • Affinity constant (KD) and binding kinetics of the recognition element
  • Color of the sensor housing
  • Operator experience

Correct Answer: Affinity constant (KD) and binding kinetics of the recognition element

Q8. Which immobilization strategy best preserves the antigen-binding orientation of antibodies to maximize active-site availability?

  • Random covalent coupling to surface lysines
  • Direct physisorption onto hydrophobic surfaces
  • Site-directed immobilization via Fc-region binding (e.g., Protein A/G or site-specific tags)
  • Crosslinking with glutaraldehyde without blocking

Correct Answer: Site-directed immobilization via Fc-region binding (e.g., Protein A/G or site-specific tags)

Q9. In aptamer-based sensors, SELEX is used primarily to:

  • Measure electrochemical current from nucleic acids
  • Select nucleic acid sequences with high affinity and specificity for the target
  • Immobilize aptamers onto gold surfaces
  • Label the aptamer with fluorescent dyes

Correct Answer: Select nucleic acid sequences with high affinity and specificity for the target

Q10. Which issue is a common limitation when using whole cells as recognition elements in biosensors?

  • Extremely high thermal stability
  • Complexity of signal interpretation and lower specificity due to multiple receptors
  • Inability to respond to small molecules
  • Absolute resistance to biofouling

Correct Answer: Complexity of signal interpretation and lower specificity due to multiple receptors

Q11. Which property describes a high-affinity interaction relevant for biosensor selectivity?

  • High dissociation rate constant (koff)
  • Low KD value
  • Rapid non-specific adsorption
  • High hydrophobicity of the ligand

Correct Answer: Low KD value

Q12. Which recognition element is most suitable for repeated regeneration cycles under mild chemical conditions?

  • Native antibodies without engineered stability
  • Molecularly imprinted polymers (MIPs)
  • Fragile enzyme conjugates
  • Live cell-based receptors

Correct Answer: Molecularly imprinted polymers (MIPs)

Q13. Which statement about lectins as recognition elements is correct?

  • Lectins bind specifically to nucleic acid sequences
  • Lectins are carbohydrate-binding proteins useful for glycan detection
  • Lectins always provide enzymatic signal amplification
  • Lectins are synthetic polymers mimicking antibodies

Correct Answer: Lectins are carbohydrate-binding proteins useful for glycan detection

Q14. Which immobilization spacer property is most important to minimize steric hindrance and maintain recognition element activity?

  • Extremely short rigid linkers that keep molecule close to surface
  • Flexible hydrophilic spacers of adequate length to extend the ligand away from the surface
  • Hydrophobic chains that pack tightly on the surface
  • Large bulky groups at binding site

Correct Answer: Flexible hydrophilic spacers of adequate length to extend the ligand away from the surface

Q15. Which advantage do aptamers have over antibodies for biosensor platforms?

  • Unlimited catalytic turnover
  • Ease of chemical synthesis, thermal stability and facile chemical modification
  • Guaranteed in vivo stability without modification
  • Intrinsic fluorescent properties

Correct Answer: Ease of chemical synthesis, thermal stability and facile chemical modification

Q16. Which detection method is generally label-free and commonly used to study binding of recognition elements in real time?

  • ELISA with enzyme labels
  • Surface plasmon resonance (SPR)
  • Fluorescence polarization with labeled ligands
  • Colorimetric strip tests

Correct Answer: Surface plasmon resonance (SPR)

Q17. What is the main purpose of blocking agents (e.g., BSA) after immobilizing a recognition element on a sensor surface?

  • To increase the surface roughness
  • To prevent non-specific adsorption and reduce background signal
  • To covalently crosslink the recognition element further
  • To denature the immobilized protein for better access

Correct Answer: To prevent non-specific adsorption and reduce background signal

Q18. Which parameter should be optimized to improve sensor response time for a recognition element with slow binding kinetics?

  • Increase surface area and reduce diffusion distance (microfluidics or nanostructuring)
  • Decrease analyte concentration
  • Use non-specific blockers extensively
  • Eliminate washing steps entirely

Correct Answer: Increase surface area and reduce diffusion distance (microfluidics or nanostructuring)

Q19. Which approach helps reduce cross-reactivity when designing biosensors for structurally related drug analytes?

  • Use a single generic receptor without selectivity testing
  • Employ highly selective recognition elements (e.g., monoclonal antibodies or carefully selected aptamers) and perform negative SELEX or counter-selection
  • Rely solely on signal amplification to overcome cross-reactivity
  • Maximize non-specific adsorption to capture all analytes

Correct Answer: Employ highly selective recognition elements (e.g., monoclonal antibodies or carefully selected aptamers) and perform negative SELEX or counter-selection

Q20. Which synthetic recognition element mimics natural receptor binding pockets and is often used when biological ligands are unstable?

  • Lectins isolated from plants
  • Molecularly imprinted polymers (MIPs)
  • Native cell membranes
  • Whole monoclonal antibodies

Correct Answer: Molecularly imprinted polymers (MIPs)

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