Q.1 Which serological technique uses a microtiter plate coated with antigen to detect antibodies in a patient’s serum?
Western blot
ELISA
Agglutination
Hemagglutination inhibition
Explanation - Enzyme‑Linked Immunosorbent Assay (ELISA) is performed on microtiter plates where antigens are immobilized to capture specific antibodies from serum.
Correct answer is: ELISA
Q.2 What is the primary advantage of a chemiluminescence immunoassay over a colorimetric ELISA?
Higher sample volume
Lower cost
Greater sensitivity
Faster incubation times
Explanation - Chemiluminescence assays emit light, providing a larger dynamic range and lower detection limits compared to color changes in ELISA.
Correct answer is: Greater sensitivity
Q.3 In a lateral flow immunochromatographic test, what component is responsible for the movement of the sample across the strip?
Conjugate pad
Nitrocellulose membrane
Absorbent pad
Buffer solution
Explanation - The absorbent pad acts as a wick, drawing liquid by capillary action through the membrane where the test and control lines are located.
Correct answer is: Absorbent pad
Q.4 Which electrical parameter is most commonly monitored in electrochemical immunosensors to quantify antibody binding?
Impedance
Capacitance
Voltage
Temperature
Explanation - Binding events at the electrode surface alter the interfacial impedance, which can be measured by electrochemical impedance spectroscopy.
Correct answer is: Impedance
Q.5 What is the purpose of a blocking step in ELISA protocols?
To wash unbound antibodies
To prevent nonspecific binding
To immobilize secondary antibodies
To amplify the signal
Explanation - Blocking proteins (e.g., BSA) cover unused sites on the plate, reducing background noise by preventing nonspecific adsorption.
Correct answer is: To prevent nonspecific binding
Q.6 Which of the following is NOT a typical detection format in immunochromatographic strips?
Gold nanoparticles
Colloidal silver
Quantum dots
Fluorescent microspheres
Explanation - While quantum dots are used in lab‑based assays, immunochromatographic strips usually employ gold, silver, or fluorescent microspheres for visual readout.
Correct answer is: Quantum dots
Q.7 In a radioimmunoassay, the “displacement curve” is generated by adding which substance to the mixture?
Unlabeled antigen
Unlabeled antibody
Radioactive tracer
Enzyme conjugate
Explanation - Adding increasing amounts of unlabeled antigen competes with the radiolabeled antigen for antibody binding, producing the displacement curve.
Correct answer is: Unlabeled antigen
Q.8 Which sensor architecture is most suitable for multiplexed serological detection?
Single‑channel potentiostat
Microfluidic chip with multiple electrodes
Handheld glucometer
Mechanical resonator
Explanation - Microfluidic platforms can spatially separate multiple reactions, allowing simultaneous detection of several analytes on a single chip.
Correct answer is: Microfluidic chip with multiple electrodes
Q.9 What is the primary function of a wash buffer in a Western blot procedure?
To fix the proteins to the membrane
To block nonspecific sites
To remove unbound antibodies
To enhance chemiluminescence
Explanation - Wash buffers clear away any antibodies that have not specifically bound to the target proteins, reducing background.
Correct answer is: To remove unbound antibodies
Q.10 Which parameter is directly proportional to the rate of signal generation in a fluorescence‑based immunoassay?
Excitation light intensity
Sample temperature
Antibody concentration
Buffer pH
Explanation - Higher antibody concentrations lead to more fluorophore‑conjugated antibodies binding, increasing fluorescence output.
Correct answer is: Antibody concentration
Q.11 In a sandwich ELISA, what is the role of the capture antibody?
To bind the detection antibody
To capture the target antigen
To produce the enzymatic signal
To block nonspecific binding
Explanation - The capture antibody is immobilized on the plate and binds the antigen; the detection antibody then binds another epitope on that antigen.
Correct answer is: To capture the target antigen
Q.12 Which type of electrode material is most commonly used in amperometric immunosensors?
Gold
Glassy carbon
Platinum
Silver/silver‑chloride
Explanation - Gold electrodes allow for stable thiol‑based immobilization of antibodies and are widely used in amperometric detection.
Correct answer is: Gold
Q.13 What is the main limitation of traditional agglutination tests?
Requires radioactive labeling
Low sensitivity
Long incubation times
Inability to quantify antigen
Explanation - Agglutination relies on visible clumping, which may miss low‑level antigen/antibody concentrations.
Correct answer is: Low sensitivity
Q.14 Which of the following is a key advantage of using microplate readers for ELISA?
Higher sample volume
Reduced reagent consumption
Direct visual readout
No need for washing steps
Explanation - Microplate formats use small volumes, lowering reagent cost and enabling high‑throughput assays.
Correct answer is: Reduced reagent consumption
Q.15 What component of a flow cytometry immunoassay provides the fluorescence signal?
Laser excitation
Detector photomultiplier
Sample buffer
Staining reagent
Explanation - The laser excites fluorophores conjugated to antibodies, producing measurable fluorescence in the detector.
Correct answer is: Laser excitation
Q.16 Which parameter is most critical for minimizing noise in an electrochemical impedance spectroscopy setup?
High‑frequency AC signal
Stable temperature
Low‑pass filter
Proper shielding
Explanation - Electromagnetic interference can dominate the weak impedance changes; shielding reduces such external noise.
Correct answer is: Proper shielding
Q.17 The limit of detection (LOD) in a serological assay is defined as:
The lowest concentration that produces a detectable signal
The highest concentration that can be measured accurately
The concentration at which the assay is most linear
The concentration that gives the strongest signal
Explanation - LOD refers to the smallest amount of analyte that can be distinguished from background noise.
Correct answer is: The lowest concentration that produces a detectable signal
Q.18 Which of the following best describes a competitive ELISA?
Two antibodies bind to the same antigen
The sample competes with a labeled antigen for antibody binding
The signal increases with antigen concentration
It uses two different enzymes for detection
Explanation - In competitive ELISA, the presence of target antigen reduces the binding of the labeled antigen to the capture antibody.
Correct answer is: The sample competes with a labeled antigen for antibody binding
Q.19 Which electronic component is essential for converting an analog sensor signal into a digital value in a biosensor system?
Transistor amplifier
Analog‑to‑Digital Converter (ADC)
Digital‑to‑Analog Converter (DAC)
Oscilloscope
Explanation - An ADC samples the continuous analog output of the sensor and produces a digital representation for microcontroller processing.
Correct answer is: Analog‑to‑Digital Converter (ADC)
Q.20 What is the main purpose of the standard curve in a quantitative ELISA?
To validate the assay kit
To calibrate the plate reader
To translate optical density to antigen concentration
To determine the incubation time
Explanation - The standard curve relates known antigen concentrations to measured absorbance, enabling quantification of unknown samples.
Correct answer is: To translate optical density to antigen concentration
Q.21 In immunoelectrodes, a common strategy for immobilizing antibodies is via:
Covalent attachment to gold using cysteine residues
Electrostatic adsorption onto carbon fibers
Physical entrapment in polymer matrix
Hydrophobic interactions with the electrode surface
Explanation - The thiol‑gold bond provides a robust, oriented attachment for antibodies on gold electrodes.
Correct answer is: Covalent attachment to gold using cysteine residues
Q.22 Which of the following best characterizes a lateral flow immunoassay’s detection limit?
It is higher than that of ELISA
It is similar to that of ELISA
It is lower than that of ELISA
It cannot be determined
Explanation - Lateral flow tests typically have higher detection limits (lower sensitivity) due to visual readout limitations.
Correct answer is: It is higher than that of ELISA
Q.23 What is the main advantage of using a microfluidic immunoassay platform?
Simplified sample preparation
Reduced reagent usage
Higher throughput
All of the above
Explanation - Microfluidics allow precise control of small volumes, enabling fast, low‑cost, and high‑throughput assays.
Correct answer is: All of the above
Q.24 Which type of antibody is typically used as the detection antibody in a sandwich ELISA?
Monoclonal antibody
Polyclonal antibody
Both monoclonal and polyclonal
None of the above
Explanation - Both can be used; the choice depends on specificity, availability, and assay design.
Correct answer is: Both monoclonal and polyclonal
Q.25 What electrical measurement is most sensitive to changes in the thickness of a biofilm on an electrode?
Capacitance
Resistance
Inductance
Voltage drop
Explanation - A biofilm adds dielectric material, altering the capacitance measured across the electrode interface.
Correct answer is: Capacitance
Q.26 Which component of an immunoassay kit typically contains the substrate that turns color in an ELISA?
Wash buffer
Detection antibody
Chromogenic substrate
Blocking solution
Explanation - The substrate reacts with the enzyme conjugate to produce a colored product that is measured spectrophotometrically.
Correct answer is: Chromogenic substrate
Q.27 The term "sensitivity" in a serological test refers to:
The ability to detect true positives
The ability to detect true negatives
The speed of the assay
The ease of interpretation
Explanation - Sensitivity is the proportion of infected individuals correctly identified by the test.
Correct answer is: The ability to detect true positives
Q.28 Which of the following is a common interference in ELISA due to sample matrix effects?
High lipid content
High hemoglobin levels
High bilirubin
All of the above
Explanation - Lipids, hemoglobin, and bilirubin can all interfere with antibody binding or signal detection.
Correct answer is: All of the above
Q.29 Which electronic technique can be used to differentiate between specific and nonspecific binding in a biosensor?
Frequency sweep in impedance spectroscopy
DC voltage sweep
Capacitance‑voltage profiling
Temperature cycling
Explanation - Specific binding often shows characteristic frequency‑dependent impedance changes compared to nonspecific interactions.
Correct answer is: Frequency sweep in impedance spectroscopy
Q.30 What is the purpose of a calibration curve in a chemiluminescence immunoassay?
To determine the assay’s dynamic range
To correct for day‑to‑day signal drift
To quantify analyte concentration from light output
All of the above
Explanation - The calibration curve links light intensity to analyte concentration and helps adjust for assay variability.
Correct answer is: All of the above
Q.31 Which of the following best describes a multiplex serological assay?
Simultaneous detection of multiple antibodies in one sample
Multiple rounds of the same assay
Testing multiple samples in parallel
Using multiple detection enzymes
Explanation - Multiplex assays can detect several targets concurrently, saving time and reagents.
Correct answer is: Simultaneous detection of multiple antibodies in one sample
Q.32 Which of these is a major challenge in developing portable immunoassay devices?
Maintaining reagent stability
Ensuring high sensitivity
Integrating power supply
All of the above
Explanation - Portability demands stable reagents, sensitive detection, and a compact power source.
Correct answer is: All of the above
Q.33 In a flow‑through ELISA, the sample is:
Pushed through the plate by pressure
Applied by pipette and allowed to sit
Rotated to promote mixing
Mixed with enzyme conjugate before application
Explanation - Flow‑through ELISA uses a vacuum or pressure to force the sample through the microtiter wells, speeding up incubation.
Correct answer is: Pushed through the plate by pressure
Q.34 Which parameter of a potentiostat must be set to zero to prevent electrode oxidation during amperometric detection?
Open‑circuit potential
Reference electrode potential
Counter electrode potential
Working electrode potential
Explanation - Setting the reference potential to a known value stabilizes the working electrode potential against undesired oxidation.
Correct answer is: Reference electrode potential
Q.35 The main source of background signal in a fluorescence‑based immunoassay is:
Unbound fluorophores
Photobleaching
Non‑specific antibody binding
Ambient light
Explanation - Non‑specific binding of fluorescent antibodies to the plate surface increases baseline fluorescence.
Correct answer is: Non‑specific antibody binding
Q.36 Which of the following is NOT a type of enzyme conjugate used in ELISA?
HRP (horseradish peroxidase)
ALP (alkaline phosphatase)
GOX (glucose oxidase)
Lactase
Explanation - Lactase is not commonly used as a reporter enzyme in ELISA; HRP, ALP, and GOX are typical choices.
Correct answer is: Lactase
Q.37 What does the term 'LOD' stand for in the context of serological testing?
Limit Of Detection
Low Output Device
Large Output Detector
Limited Operational Duration
Explanation - LOD is the smallest quantity of analyte that can be reliably distinguished from background noise.
Correct answer is: Limit Of Detection
Q.38 Which of these best describes a ‘capture antibody’ in a sandwich ELISA?
Antibody immobilized on the plate to bind antigen
Antibody used to detect antigen after it has bound
Antibody that cross‑reacts with non‑target proteins
None of the above
Explanation - The capture antibody is fixed to the microtiter wells and sequesters the antigen for subsequent detection.
Correct answer is: Antibody immobilized on the plate to bind antigen
Q.39 Which technique is most suitable for detecting antigens directly without antibodies?
Direct ELISA
Indirect ELISA
Sandwich ELISA
Competitive ELISA
Explanation - Direct ELISA uses a labeled primary antibody that binds directly to the target antigen.
Correct answer is: Direct ELISA
Q.40 In an immunoassay, the ‘signal-to-noise ratio’ (SNR) is:
Signal divided by background noise
Noise divided by signal
Signal plus noise
Signal minus noise
Explanation - Higher SNR indicates a clearer, more reliable assay result.
Correct answer is: Signal divided by background noise
Q.41 What type of measurement is typically used to monitor antibody binding in a quartz crystal microbalance (QCM) sensor?
Mass change
Electrical resistance
Optical density
Temperature
Explanation - QCM detects changes in mass on the crystal surface, which correspond to antibody‑antigen interactions.
Correct answer is: Mass change
Q.42 Which of these is a characteristic of a well‑performed immunoprecipitation experiment?
High nonspecific binding
Low signal intensity
Specific precipitation of target protein
Absence of washing steps
Explanation - Immunoprecipitation selectively pulls down the target protein using an antibody, minimizing background.
Correct answer is: Specific precipitation of target protein
Q.43 The main advantage of using a microtiter plate over a 96‑well format is:
Higher volume capacity
Higher surface area per well
Fewer wells
Lower cost
Explanation - Larger well plates can accommodate greater sample volumes for high‑throughput screening.
Correct answer is: Higher volume capacity
Q.44 Which electronic component is responsible for converting analog sensor output into a digital signal suitable for microcontroller processing?
Analog‑to‑Digital Converter (ADC)
Digital‑to‑Analog Converter (DAC)
Operational amplifier
Microprocessor
Explanation - An ADC samples and quantizes the continuous sensor voltage into a digital number for computation.
Correct answer is: Analog‑to‑Digital Converter (ADC)
Q.45 What is the purpose of a washing step in a Western blot?
To fix proteins onto the membrane
To remove unbound antibodies
To increase membrane permeability
To enhance chemiluminescence
Explanation - Washing clears excess antibodies, reducing background and improving signal specificity.
Correct answer is: To remove unbound antibodies
Q.46 Which of the following is an example of a label-free serological detection method?
Surface Plasmon Resonance (SPR)
ELISA
Western blot
Fluorescence microscopy
Explanation - SPR measures changes in refractive index upon binding without fluorescent or enzymatic labels.
Correct answer is: Surface Plasmon Resonance (SPR)
Q.47 Which of the following parameters is most critical when designing a microfluidic immunoassay chip?
Channel width
Surface roughness
Fluid viscosity
All of the above
Explanation - Fluidic dynamics, surface properties, and fluid characteristics all influence assay performance.
Correct answer is: All of the above
Q.48 The primary function of a blocking buffer in ELISA is to:
Prevent nonspecific binding
Stabilize enzymes
Neutralize pH
Dilute the sample
Explanation - Blocking proteins cover unreactive sites on the plate to reduce background signal.
Correct answer is: Prevent nonspecific binding
Q.49 Which of the following is a disadvantage of using radioactive labels in immunoassays?
High sensitivity
Short half‑life of radioisotopes
Complex disposal requirements
All of the above
Explanation - Radioactive assays are sensitive but pose regulatory, safety, and logistical challenges.
Correct answer is: All of the above
Q.50 In amperometric immunosensors, the current signal is directly proportional to:
Concentration of the analyte
Temperature of the solution
Electrode surface area
Buffer ionic strength
Explanation - Binding of the target induces a measurable change in current that scales with analyte concentration.
Correct answer is: Concentration of the analyte
Q.51 Which component of the ELISA detection system provides the chromogenic reaction?
Substrate solution
Secondary antibody
Blocking buffer
Wash buffer
Explanation - The substrate reacts with the enzyme conjugated to the detection antibody to produce a color change.
Correct answer is: Substrate solution
Q.52 What is the main advantage of a chemiluminescent ELISA over a colorimetric ELISA?
Lower cost
Higher sensitivity
Shorter incubation time
No need for washing
Explanation - Chemiluminescence offers a broader dynamic range and lower background, improving sensitivity.
Correct answer is: Higher sensitivity
Q.53 Which of the following best describes a biosensor’s ‘sensing element’?
The transducer converting biological interaction to electrical signal
The electronic circuitry processing the signal
The housing protecting the device
The data‑analysis software
Explanation - The sensing element detects the specific biomolecular event and converts it into a measurable electrical response.
Correct answer is: The transducer converting biological interaction to electrical signal
Q.54 In an immunochromatographic strip, the test line is typically:
Coated with the target antigen
Coated with capture antibodies
Coated with conjugate antibodies
Coated with blocking buffer
Explanation - The test line contains antibodies that bind the antigen–antibody conjugate, forming a visible line.
Correct answer is: Coated with capture antibodies
Q.55 Which of the following is NOT a common sample type for serological assays?
Blood serum
Urine
Saliva
Cerebrospinal fluid
Explanation - Urine is rarely used for antibody detection; serology typically relies on blood or other bodily fluids.
Correct answer is: Urine
Q.56 The key benefit of multiplexed serological assays is:
Reduced reagent consumption
Higher detection limits
Longer assay times
Single‑target focus
Explanation - Multiplexing allows simultaneous detection of many targets using the same sample volume.
Correct answer is: Reduced reagent consumption
Q.57 What is the purpose of a standard curve in a quantitative immunoassay?
To verify reagent quality
To convert signal to analyte concentration
To determine assay specificity
To calibrate the microplate reader
Explanation - A standard curve links measured signals (e.g., absorbance) to known concentrations, enabling quantification of unknowns.
Correct answer is: To convert signal to analyte concentration
Q.58 Which of the following is a common source of false positives in serological tests?
Cross‑reactive antibodies
Instrument drift
Incorrect sample handling
All of the above
Explanation - Antibodies that bind to similar epitopes on unrelated proteins can trigger erroneous signals.
Correct answer is: Cross‑reactive antibodies
Q.59 In an amperometric immunosensor, the detection limit is primarily influenced by:
The electrode surface area
The diffusion coefficient of the analyte
The signal‑to‑noise ratio
All of the above
Explanation - Sensitivity depends on electrode design, mass transport, and electronic noise characteristics.
Correct answer is: All of the above
Q.60 Which of the following is a key step in preparing an antibody for use in an ELISA?
Dialysis against PBS
Conjugation with HRP
Heat inactivation
Freeze‑thaw cycles
Explanation - Conjugating the antibody to an enzyme allows detection via a chromogenic reaction.
Correct answer is: Conjugation with HRP
Q.61 In a sandwich ELISA, the detection antibody must:
Bind to the same epitope as the capture antibody
Bind to a different epitope on the antigen
Bind only to the enzyme substrate
Bind to the microplate surface
Explanation - The detection antibody must target another site on the antigen to form the sandwich complex.
Correct answer is: Bind to a different epitope on the antigen
Q.62 What type of detection is typically used in a rapid lateral flow test for COVID‑19 antibodies?
Enzyme‑linked chromogenic
Gold nanoparticle colloidal
Radioactive
Fluorescent dye
Explanation - Gold nanoparticles provide a visible red line, allowing quick visual interpretation.
Correct answer is: Gold nanoparticle colloidal
Q.63 Which of the following is a major advantage of using a microchip-based electrochemical immunosensor?
Large sample volume requirement
Long assay time
High integration and automation
Complex fabrication process
Explanation - Microchips enable miniaturization, parallel processing, and automated readouts.
Correct answer is: High integration and automation
Q.64 In a flow cytometry immunoassay, the fluorescence intensity of a bead correlates with:
The number of target molecules bound
The size of the bead
The flow speed
The temperature of the buffer
Explanation - More binding events produce higher fluorescence, allowing quantitation.
Correct answer is: The number of target molecules bound
Q.65 Which of the following best describes the function of a secondary antibody in an ELISA?
Binds directly to the antigen
Binds to the capture antibody
Binds to the detection antibody
Binds to the enzyme substrate
Explanation - The secondary antibody is conjugated to an enzyme and recognizes the detection antibody, amplifying the signal.
Correct answer is: Binds to the detection antibody
Q.66 In a chemiluminescence immunoassay, the substrate is typically:
A peroxide
A metal salt
A reducing agent
A carbohydrate
Explanation - Peroxide substrates (e.g., luminol) react with HRP to generate light.
Correct answer is: A peroxide
Q.67 Which of the following is NOT a typical output from an impedance‑based biosensor?
Nyquist plot
Bode plot
Fourier transform
Phase shift
Explanation - Impedance sensors produce Nyquist, Bode plots, and phase data; a Fourier transform is not directly an output.
Correct answer is: Fourier transform
Q.68 What is the main benefit of a microfluidic immunoassay over a conventional ELISA?
Higher detection limits
Longer assay time
Reduced reagent consumption
None of the above
Explanation - Microfluidic devices use microliter volumes, cutting reagent use dramatically.
Correct answer is: Reduced reagent consumption
Q.69 Which of the following is a common signal amplification strategy in immunoassays?
Using a secondary antibody
Increasing incubation time
Changing the buffer pH
Diluting the sample
Explanation - A secondary antibody conjugated to an enzyme or fluorophore amplifies the detection signal.
Correct answer is: Using a secondary antibody
Q.70 What is the primary purpose of a wash buffer in a lateral flow test?
To rinse away excess sample
To enhance antibody binding
To maintain buffer pH
To immobilize the test line
Explanation - Washing removes unbound reagents, reducing background and improving line visibility.
Correct answer is: To rinse away excess sample
Q.71 Which of the following best describes the principle of an electrochemical immunosensor using a potentiostat?
Measuring changes in voltage due to binding
Measuring changes in current under a fixed potential
Measuring temperature shifts
Measuring mass changes on a cantilever
Explanation - A potentiostat maintains a constant potential and records the resulting current, which varies with analyte binding.
Correct answer is: Measuring changes in current under a fixed potential
Q.72 Which component of a microfluidic chip is responsible for channeling the sample to the detection region?
Valves
Mixing chamber
Channel walls
Fluidic pump
Explanation - Microfluidic channels guide the fluid flow via geometry and surface properties.
Correct answer is: Channel walls
Q.73 In a radioimmunoassay, the radioisotope typically labels:
The antibody
The antigen
The enzyme
The buffer
Explanation - Radioactive isotopes are attached to antigen molecules, allowing detection of binding events.
Correct answer is: The antigen
Q.74 Which of the following is a typical readout method for a fluorescence immunoassay?
Plate reader fluorescence detection
Mass spectrometry
X‑ray diffraction
NMR spectroscopy
Explanation - Fluorescence microplate readers measure emitted light at specific wavelengths.
Correct answer is: Plate reader fluorescence detection
Q.75 What does the term 'limit of quantitation' (LOQ) refer to in serological assays?
Lowest amount that can be detected
Highest amount that can be measured
Lowest concentration that can be quantified with acceptable precision
Time required to obtain a result
Explanation - LOQ is higher than LOD, representing the lowest analyte level that can be measured accurately.
Correct answer is: Lowest concentration that can be quantified with acceptable precision
Q.76 Which of the following is a common electrode modification to improve antibody immobilization?
Polydopamine coating
Nickel deposition
Silica layer
Graphite coating
Explanation - Polydopamine forms a bioadhesive surface that facilitates covalent bonding of antibodies.
Correct answer is: Polydopamine coating
Q.77 What is the primary reason for using a blocking step after coating a microtiter plate in ELISA?
To remove unbound antigens
To prevent non‑specific adsorption of proteins
To increase enzyme activity
To stabilize the pH
Explanation - Blocking reduces background by covering unused sites on the plate surface.
Correct answer is: To prevent non‑specific adsorption of proteins
Q.78 In a multiplex flow cytometry assay, beads are often labeled with:
Different fluorescent dyes
Different sizes
Different magnetic properties
Different electrical potentials
Explanation - Distinct dyes allow simultaneous detection of multiple targets in a single tube.
Correct answer is: Different fluorescent dyes
Q.79 Which of the following is a key advantage of label‑free biosensors over labeled immunoassays?
Higher sensitivity
Faster results
No need for conjugates
All of the above
Explanation - Label‑free techniques detect binding directly, simplifying assay design.
Correct answer is: No need for conjugates
Q.80 What is the main function of a secondary antibody in a sandwich ELISA?
Capture the antigen
Detect the antigen
Bind the capture antibody
Provide the chromogenic substrate
Explanation - The secondary antibody binds to the detection antibody and carries the enzyme for signal generation.
Correct answer is: Detect the antigen
Q.81 Which of the following best describes a chemiluminescence immunoassay’s detection principle?
Emission of light by a substrate–enzyme reaction
Absorption of light by a chromogenic substrate
Fluorescence of a labeled antibody
Color change of a precipitate
Explanation - Chemiluminescence assays generate light as a direct readout of enzyme activity.
Correct answer is: Emission of light by a substrate–enzyme reaction
Q.82 In a competitive ELISA, higher concentrations of the target analyte result in:
Higher signal
Lower signal
No change in signal
Variable signal depending on incubation time
Explanation - Target competes with the labeled antigen, reducing signal intensity.
Correct answer is: Lower signal
Q.83 Which of the following is a major consideration when integrating a biosensor into a portable device?
Battery life
Signal stability
User interface
All of the above
Explanation - Portability demands efficient power usage, stable signals, and user‑friendly operation.
Correct answer is: All of the above
Q.84 In a flow‑through ELISA, the sample is:
Pushed through the plate by vacuum
Applied by pipette and left to sit
Stirred continuously
Diluted in buffer before application
Explanation - Vacuum accelerates sample movement, shortening incubation time.
Correct answer is: Pushed through the plate by vacuum
Q.85 What is the primary role of the wash buffer in a Western blot?
To fix proteins to the membrane
To remove unbound antibodies
To block nonspecific sites
To enhance chemiluminescence
Explanation - Washing reduces background by removing antibodies that did not bind specific targets.
Correct answer is: To remove unbound antibodies
Q.86 Which of the following is a common method to immobilize antibodies on a gold electrode?
Covalent attachment via EDC/NHS chemistry
Hydrophobic adsorption
Electrostatic attraction to silica
Physical entrapment in polymer
Explanation - EDC/NHS chemistry forms stable amide bonds between antibody amines and carboxylated surfaces.
Correct answer is: Covalent attachment via EDC/NHS chemistry
Q.87 Which of the following best describes a 'capture antibody' in a sandwich ELISA?
Antibody that binds the target antigen and is immobilized on the plate
Antibody that is labeled with an enzyme
Antibody that blocks nonspecific binding
Antibody that competes with the target
Explanation - The capture antibody is fixed to the well surface to anchor the antigen for detection.
Correct answer is: Antibody that binds the target antigen and is immobilized on the plate
Q.88 What is the main disadvantage of using radioactive labels in immunoassays?
Short half‑life
Safety and disposal issues
High cost
All of the above
Explanation - Radioactive assays pose safety, regulatory, and logistical challenges despite their sensitivity.
Correct answer is: All of the above
Q.89 Which of the following is a typical application of a microfluidic immunoassay platform?
High‑throughput drug screening
Large‑scale industrial production
Whole‑body imaging
Genetic sequencing
Explanation - Microfluidic devices allow parallel testing of many samples in drug discovery.
Correct answer is: High‑throughput drug screening
Q.90 Which component of an immunoassay kit is used to produce a chromogenic signal?
Chromogenic substrate
Secondary antibody
Blocking buffer
Wash buffer
Explanation - The substrate reacts with the enzyme on the detection antibody to create a visible color change.
Correct answer is: Chromogenic substrate
Q.91 In an ELISA, which step is performed last?
Blocking
Incubation with detection antibody
Incubation with sample
Washing
Explanation - The detection antibody is added after sample incubation and washing to bind the captured antigen.
Correct answer is: Incubation with detection antibody
Q.92 Which of the following is a common feature of a flow‑through ELISA?
Use of magnetic beads
Use of a vacuum to speed up sample flow
Use of radioactive labeling
Use of large volumes
Explanation - Vacuum-driven flow accelerates binding and washing steps.
Correct answer is: Use of a vacuum to speed up sample flow
Q.93 In a chemiluminescent ELISA, the light output is typically measured by:
A photomultiplier tube
A spectrophotometer
A flow cytometer
An optical fiber sensor
Explanation - Photomultiplier tubes detect the low-intensity light emitted by chemiluminescent reactions.
Correct answer is: A photomultiplier tube
Q.94 Which of the following best describes a lateral flow immunoassay?
A laboratory-based plate assay
A point‑of‑care test with a strip format
An electrophoresis technique
A mass spectrometry method
Explanation - Lateral flow uses capillary action across a strip to separate and detect analytes.
Correct answer is: A point‑of‑care test with a strip format
Q.95 In a multiplex immunoassay, the detection of multiple analytes is achieved by:
Different colored substrates
Distinct antibody pairs on separate spots
Sequential incubation steps
Multiple microplates
Explanation - Each analyte is captured by a specific antibody pair in a spatially resolved array.
Correct answer is: Distinct antibody pairs on separate spots
Q.96 What is the typical role of a blocking buffer in ELISA?
Prevent non‑specific protein adsorption
Enhance enzyme activity
Stabilize pH
Reduce background noise
Explanation - Blocking proteins occupy unreacted sites, reducing nonspecific binding.
Correct answer is: Prevent non‑specific protein adsorption
Q.97 Which of the following is NOT a typical component of an immunoassay?
Capture antibody
Detection antibody
Enzyme conjugate
X‑ray crystal
Explanation - X‑ray crystals are used for structure determination, not routine immunoassay kits.
Correct answer is: X‑ray crystal
Q.98 What does the term 'sandwich ELISA' refer to?
ELISA using two antibodies that bind different epitopes of the same antigen
ELISA where the antigen is sandwiched between two enzymes
ELISA performed in a sandwich‑shaped plate
ELISA with a sandwich of detection and capture antibodies on the same well
Explanation - The capture and detection antibodies form a sandwich around the antigen.
Correct answer is: ELISA using two antibodies that bind different epitopes of the same antigen
Q.99 Which of the following is a typical signal amplification strategy in immunoassays?
Use of a secondary antibody
Increased incubation temperature
Higher sample volume
Longer detection time
Explanation - A secondary antibody conjugated to an enzyme or fluorophore amplifies the signal.
Correct answer is: Use of a secondary antibody
Q.100 Which of the following is a common detection method for a fluorescence‑based immunoassay?
Plate reader fluorescence detection
Mass spectrometry
NMR spectroscopy
X‑ray diffraction
Explanation - Fluorescence microplate readers measure emitted light at specific wavelengths.
Correct answer is: Plate reader fluorescence detection
Q.101 In a competitive ELISA, the signal intensity is:
Directly proportional to analyte concentration
Inversely proportional to analyte concentration
Independent of analyte concentration
Dependent on incubation time only
Explanation - High analyte levels compete with labeled antigen, decreasing signal.
Correct answer is: Inversely proportional to analyte concentration
Q.102 Which of the following is a key advantage of label‑free biosensors?
Simplified assay design
No requirement for conjugates
Potential for real‑time monitoring
All of the above
Explanation - Label‑free sensors detect binding directly, enabling simple, rapid, and real‑time analyses.
Correct answer is: All of the above
Q.103 Which of the following is a major challenge in developing portable serological tests?
Maintaining reagent stability
Ensuring high sensitivity
Integrating a user‑friendly interface
All of the above
Explanation - Portability requires stable reagents, sensitivity, and ease of use.
Correct answer is: All of the above
Q.104 What type of sensor transduces changes in the dielectric constant due to antigen‑antibody binding?
Capacitance‑based sensor
Inductive sensor
Resistive sensor
Thermocouple
Explanation - A dielectric layer changes the capacitance when the antigen binds.
Correct answer is: Capacitance‑based sensor
Q.105 Which of the following is a typical component of a chemiluminescence substrate?
Luminol
Glucose
Alkaline phosphatase
Hemoglobin
Explanation - Luminol reacts with HRP to generate light in chemiluminescence.
Correct answer is: Luminol
Q.106 What does the term 'signal‑to‑noise ratio' (SNR) refer to in a biosensor?
Signal divided by background noise
Noise divided by signal
Signal plus noise
Signal minus noise
Explanation - A higher SNR indicates a clearer, more reliable measurement.
Correct answer is: Signal divided by background noise
Q.107 In a flow cytometry assay, the fluorescence intensity of a bead is proportional to:
Number of target molecules bound
Bead size
Flow speed
Buffer temperature
Explanation - More bound analyte leads to higher fluorescence signal.
Correct answer is: Number of target molecules bound
Q.108 Which of the following is a key advantage of using a microplate reader for ELISA?
High throughput
Low reagent consumption
Precise temperature control
All of the above
Explanation - Microplate readers enable rapid, automated, and accurate measurements.
Correct answer is: All of the above
Q.109 What is the main purpose of a wash buffer in a lateral flow assay?
To rinse away unbound sample
To enhance antibody binding
To maintain buffer pH
To immobilize the test line
Explanation - Washing removes excess reagents, improving signal clarity.
Correct answer is: To rinse away unbound sample
Q.110 Which of the following best describes a 'capture antibody' in an immunoassay?
Antibody that binds the antigen and is immobilized on a surface
Antibody that is labeled with an enzyme
Antibody that blocks nonspecific binding
Antibody that competes with the target antigen
Explanation - The capture antibody is fixed to capture the target antigen from the sample.
Correct answer is: Antibody that binds the antigen and is immobilized on a surface
Q.111 Which of the following is a typical component of a competitive ELISA?
Radiolabeled antigen
Labeled antibody
Enzyme‑conjugated secondary antibody
All of the above
Explanation - In competitive ELISA, the antigen is labeled and competes with sample antigen.
Correct answer is: Radiolabeled antigen
Q.112 Which of the following is a common method for immobilizing antibodies on a sensor surface?
Covalent attachment via EDC/NHS chemistry
Hydrophobic adsorption
Electrostatic attraction to silica
Physical entrapment in polymer
Explanation - This chemistry forms stable covalent bonds between antibody amines and carboxyl groups.
Correct answer is: Covalent attachment via EDC/NHS chemistry
Q.113 What does the term 'limit of detection' (LOD) refer to?
Lowest quantity of analyte that can be detected with confidence
Highest quantity of analyte that can be measured accurately
Lowest concentration that can be quantified with precision
Time required to achieve a result
Explanation - LOD is the smallest amount of analyte that stands above background noise.
Correct answer is: Lowest quantity of analyte that can be detected with confidence
Q.114 Which of the following is an advantage of a microfluidic immunoassay?
Reduced reagent consumption
Higher throughput
Faster assay times
All of the above
Explanation - Microfluidics enable efficient, rapid, and high‑throughput assays with minimal reagents.
Correct answer is: All of the above
Q.115 What is the primary purpose of the detection antibody in a sandwich ELISA?
To bind the captured antigen
To immobilize the antigen on the plate
To generate a color change
To block nonspecific sites
Explanation - The detection antibody binds to a second epitope on the antigen, forming the sandwich complex.
Correct answer is: To bind the captured antigen
Q.116 In a chemiluminescent ELISA, the light signal is generated by:
Enzyme reacting with a luminogenic substrate
Fluorescent dye emitting upon excitation
Color change in a chromogenic substrate
Precipitation of a solid product
Explanation - HRP or similar enzymes catalyze a luminescent reaction.
Correct answer is: Enzyme reacting with a luminogenic substrate
Q.117 Which of the following is a key feature of a lateral flow immunoassay?
Capillary action drives sample flow
Detection requires a plate reader
It is performed in a laboratory
It uses radioactive labeling
Explanation - The strip design relies on capillary forces to move the sample and reagents.
Correct answer is: Capillary action drives sample flow
Q.118 In a multiplex flow cytometry assay, different bead populations are distinguished by:
Distinct fluorescent dyes
Different sizes
Different magnetic properties
Different electrical potentials
Explanation - Each bead set has a unique fluorescence signature, enabling simultaneous detection.
Correct answer is: Distinct fluorescent dyes
Q.119 What is the main purpose of a blocking buffer in ELISA?
Prevent nonspecific protein adsorption
Stabilize the pH of the buffer
Increase enzyme activity
Reduce background noise
Explanation - Blocking proteins occupy unreacted sites, reducing nonspecific binding.
Correct answer is: Prevent nonspecific protein adsorption
Q.120 Which of the following is a typical readout for a fluorescent immunoassay?
Fluorescence intensity measured by a microplate reader
Mass of the analyte via mass spectrometry
Color change observed by eye
Electrical resistance change
Explanation - Fluorescence microplate readers detect emitted light from fluorophore‑conjugated antibodies.
Correct answer is: Fluorescence intensity measured by a microplate reader
Q.121 In a competitive ELISA, increasing concentrations of the target analyte will:
Increase the signal intensity
Decrease the signal intensity
Have no effect on the signal
Only affect the signal if the incubation time changes
Explanation - Higher analyte concentrations outcompete the labeled antigen, reducing the signal.
Correct answer is: Decrease the signal intensity
Q.122 Which of the following is a key advantage of label‑free biosensors?
Simplified assay design
No need for conjugates
Potential for real‑time monitoring
All of the above
Explanation - Label‑free sensors detect binding directly, eliminating conjugates and enabling real‑time analysis.
Correct answer is: All of the above
Q.123 Which component is typically used to immobilize antibodies on a gold electrode surface?
Covalent coupling via EDC/NHS
Physical adsorption
Magnetic binding
Electrostatic attraction to silica
Explanation - EDC/NHS chemistry forms stable amide bonds between antibodies and carboxylated surfaces.
Correct answer is: Covalent coupling via EDC/NHS
Q.124 What is the main purpose of the wash step in an ELISA?
To remove unbound antibodies
To fix the antigens to the plate
To block nonspecific sites
To enhance enzyme activity
Explanation - Washing clears non‑bound antibodies, reducing background noise.
Correct answer is: To remove unbound antibodies
Q.125 Which of the following is a common method for measuring the signal from a chemiluminescence immunoassay?
Photomultiplier tube
Spectrophotometer
Fluorescence microscope
Mass spectrometer
Explanation - PMTs detect the low‑level light emitted in chemiluminescence reactions.
Correct answer is: Photomultiplier tube
Q.126 Which of the following best describes a flow‑through ELISA?
The sample is pushed through the plate by vacuum
The sample is added and left to incubate without agitation
The sample is mixed with a magnetic bead
The sample is applied to a glass slide
Explanation - Vacuum‑driven flow accelerates the assay steps.
Correct answer is: The sample is pushed through the plate by vacuum
Q.127 Which of the following is a common type of substrate used in chemiluminescent ELISAs?
Luminol
NADH
HRP
Alkaline phosphatase
Explanation - Luminol reacts with HRP to produce light in chemiluminescent assays.
Correct answer is: Luminol
Q.128 What is the main advantage of a microfluidic immunoassay over a traditional ELISA?
Higher reagent consumption
Longer assay times
Reduced sample volume
Higher detection limits
Explanation - Microfluidic devices use microliter volumes, lowering reagent consumption.
Correct answer is: Reduced sample volume
Q.129 Which of the following is a key advantage of a label‑free biosensor?
No need for labeling
Rapid real‑time detection
High sensitivity
All of the above
Explanation - Label‑free methods simplify assay design and can provide rapid, sensitive detection.
Correct answer is: All of the above
Q.130 In a lateral flow assay, the test line typically contains:
Capture antibodies
Conjugate antibodies
Enzyme conjugate
Chromogenic substrate
Explanation - Capture antibodies bind the antigen–antibody conjugate, forming a visible line.
Correct answer is: Capture antibodies
Q.131 What is the function of a blocking buffer in immunoassays?
Prevent nonspecific adsorption of proteins
Stabilize the pH of the buffer
Enhance enzyme activity
Reduce background noise
Explanation - Blocking proteins occupy unreacted sites, reducing nonspecific binding and background.
Correct answer is: Prevent nonspecific adsorption of proteins
Q.132 Which of the following best describes the principle of a sandwich ELISA?
Two antibodies bind to the same epitope of an antigen
Two antibodies bind to different epitopes of the same antigen
The antigen is sandwiched between two enzymes
The antibody and antigen form a ring structure
Explanation - The capture antibody binds one epitope; the detection antibody binds another, forming a sandwich complex.
Correct answer is: Two antibodies bind to different epitopes of the same antigen
Q.133 Which of the following is a typical method for measuring the signal from an electrochemical impedance spectroscopy immunosensor?
Nyquist plot
Bode plot
Fourier transform
Phase shift
Explanation - Nyquist plots show the real vs. imaginary impedance, revealing binding events.
Correct answer is: Nyquist plot
Q.134 In a flow cytometry immunoassay, the fluorescence intensity of each bead correlates with:
The number of target molecules bound
The size of the bead
The flow speed
The buffer temperature
Explanation - Higher binding leads to increased fluorescence intensity.
Correct answer is: The number of target molecules bound
Q.135 What is the primary function of a secondary antibody in an ELISA?
Capture the target antigen
Detect the target antigen
Block nonspecific sites
Enhance enzyme activity
Explanation - The secondary antibody binds to the detection antibody and carries the enzyme for signal generation.
Correct answer is: Detect the target antigen
Q.136 Which of the following is a common detection method for a fluorescent immunoassay?
Plate reader fluorescence detection
Mass spectrometry
X‑ray diffraction
Thermal imaging
Explanation - Fluorescence microplate readers measure light emission from labeled antibodies.
Correct answer is: Plate reader fluorescence detection
Q.137 In a chemiluminescent ELISA, what is the main source of light?
Enzyme substrate reaction
Fluorescent dye excitation
Chromogenic color change
Photoluminescence from a solid
Explanation - The enzyme (e.g., HRP) catalyzes a luminogenic reaction that emits light.
Correct answer is: Enzyme substrate reaction
Q.138 Which of the following is a key feature of a microfluidic immunoassay platform?
High throughput
Low sample volume
Rapid assay times
All of the above
Explanation - Microfluidic devices enable efficient, high‑throughput, and rapid testing with minimal reagents.
Correct answer is: All of the above
Q.139 What is the main advantage of a label‑free sensor for serological detection?
Simplified assay design
No need for labeled reagents
Real‑time detection
All of the above
Explanation - Label‑free detection eliminates labeling steps and allows real‑time monitoring.
Correct answer is: All of the above
Q.140 Which of the following is a typical component of a chemiluminescence substrate?
Luminol
NADH
Glucose
Alkaline phosphatase
Explanation - Luminol reacts with HRP to produce chemiluminescence.
Correct answer is: Luminol
Q.141 What does the term 'signal‑to‑noise ratio' (SNR) mean?
Signal divided by background noise
Noise divided by signal
Signal plus noise
Signal minus noise
Explanation - A higher SNR indicates a clearer, more reliable measurement.
Correct answer is: Signal divided by background noise
Q.142 In flow cytometry, the fluorescence intensity of a bead correlates with:
Number of target molecules bound
Bead size
Flow speed
Buffer temperature
Explanation - More antigen bound leads to higher fluorescence.
Correct answer is: Number of target molecules bound
Q.143 In a sandwich ELISA, the capture antibody is:
Immobilized on the plate to bind antigen
Conjugated to an enzyme for detection
A secondary antibody
A blocking agent
Explanation - Capture antibodies anchor the antigen, allowing the detection antibody to bind.
Correct answer is: Immobilized on the plate to bind antigen
Q.144 What is the main purpose of a wash buffer?
Remove unbound antibodies
Fix antigens to the plate
Block nonspecific sites
Enhance enzyme activity
Explanation - Washing clears excess antibodies and reduces background noise.
Correct answer is: Remove unbound antibodies
Q.145 Which of the following is a key advantage of using a microplate reader for ELISA?
High throughput
Low reagent consumption
Precise temperature control
All of the above
Explanation - Microplate readers enable rapid, automated, and accurate measurements.
Correct answer is: All of the above
Q.146 In a lateral flow immunoassay, the test line contains:
Capture antibodies
Conjugate antibodies
Enzyme conjugate
Chromogenic substrate
Explanation - Capture antibodies bind the antigen–antibody conjugate, forming a visible line.
Correct answer is: Capture antibodies
Q.147 What is the primary function of the detection antibody in a sandwich ELISA?
Bind the captured antigen
Generate a color change
Block nonspecific binding
Enhance enzyme activity
Explanation - Detection antibody binds a second epitope on the antigen, forming the sandwich.
Correct answer is: Bind the captured antigen
Q.148 Which of the following is a typical readout for a chemiluminescence immunoassay?
Photomultiplier tube signal
Spectrophotometer reading
Fluorescence microscope image
Mass spectrometer output
Explanation - Photomultiplier tubes detect the low‑intensity light from chemiluminescence.
Correct answer is: Photomultiplier tube signal