Enzyme Technology Questions and Answers – Biosensors

This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “Biosensors”.

1. Which of the following statements is not true for biosensors?
a) Biosensors convert a biological signal into an electrical signal
b) Biosensors are used to determine the concentration of substances and other parameters of biological interest even where they do not utilize a biological system directly
c) Biosensors utilize the different biological systems such as enzymes, whole cell metabolism, ligand binding and the antibody-antigen reaction
d) Biosensor consists of a vessel, or series of vessels, used to perform a desired conversion by enzymic means
View Answer

Answer: d
Explanation: The statements which are true for biosensors are as follows:
• Biosensors convert a biological signal into an electrical signal.
• Biosensors are used to determine the concentration of substances and other parameters of biological interest even where they do not utilize a biological system directly.
• Biosensors utilize the different biological systems such as enzymes, whole cell metabolism, ligand binding and the antibody-antigen reaction.
“Biosensor consists of a vessel, or series of vessels, used to perform a desired conversion by enzymic means” is a false statement. It is true for enzyme reactors.
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2. Which of the following features is not possessed by biosensor?
a) The biocatalyst used in the biosensor must be highly specific for the purpose of the analyses
b) The reaction occurring in the biosensor should be as independent of such physical parameters
c) Active site is mainly constituted by non-polar amino acids for catalysis to take place
d) The response from the biosensors should be accurate, precise, reproducible and linear
View Answer

Answer: c
Explanation: Some of the features possessed by biosensors are discussed below:
• The biocatalyst used in the biosensor must be highly specific for the purpose of the analyses.
• The reaction occurring in the biosensor should be as independent of such physical parameters which allows the analysis of samples with minimal pre-treatment. Also if cofactors or coenzymes are involved, they should also be co-immobilised with the enzyme.
• The response from the biosensors should be accurate, precise, reproducible, linear over the useful analytical range and also free from electrical noise.
“Active site is mainly constituted by non-polar amino acids for catalysis to take place.” This statement is possessed by active site of the enzyme.

3. Which of the following property is not possessed by biosensors?
a) The probe used in the biosensor must be tiny and biocompatible, having no toxic or antigenic effects
b) The biosensor should be cheap, small, portable and capable of being used by semi-skilled operators
c) There should be a market for the biosensor
d) The specificity of substrate binding is mediated by spatial arrangement of atoms in an enzyme’s substrate binding site as well as substrate.
View Answer

Answer: d
Explanation: Following are the properties which a biosensor should possess:
• If the biosensor used in invasive, the probe must be tiny and biocompatible, having no toxic or antigenic effects.
• The biosensor should be cheap, small, portable and capable of being used by semi-skilled operators.
• If the traditional methods used is encouraged and the decentralization of laboratory testing is discouraged, then there is no use of producing more biosensors. Thus, there should be a market for the biosensor.
“The specificity of substrate binding is mediated by spatial arrangement of atoms in an enzyme’s substrate binding site as well as substrate.” This is a property of active site of the enzyme.

4. Immobilized enzymes are more preferred over free enzymes in producing biosensors.
a) True
b) False
View Answer

Answer: a
Explanation: Immobilized enzymes are more preferred over free enzymes in producing biosensors because of the following reasons:
• Immobilized enzymes may be re-used ensuring the same catalytic activity for a series of analyses.
• Immobilized enzymes are intrinsically stabled during the immobilization process
• Even if inactivation of enzymes occurs, it is steady and predictable
• Immobilised enzyme systems are re-usable up to 10,000 times over a period of several months which results in a considerable saving in terms of cost of the enzyme in bound state relative to that of free soluble enzymes.

5. What does the following diagram represent?

a) Packed bed reactor
b) Schematic diagram showing the main components of a biosensor
c) Chromatography
d) Lock and key model
View Answer

Answer: b
Explanation: Biosensors convert a biological signal into an electrical signal. The diagram below represents schematic diagram showing the main components of a biosensor.
In this diagram, the biocatalyst is one which converts the substrate to product. This reaction is determined by the transducer which converts it to an electrical signal. The output from the transducer is amplified, processed and displayed.

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6. If the physical change accompanying the reaction is heat output, the biosensors are referred to as _________________
a) potentiometric biosensors
b) optical biosensors
c) calorimetric biosensors
d) amperometric biosensors
View Answer

Answer: c
Explanation: If the physical change accompanying the reaction is heat output, the biosensors are referred to as calorimetric biosensors. In potentiometric biosensors, changes in the distribution of charges causes an electrical potential to be produced. Optical biosensors are those in which light output during the reaction is the physical change. In amperometric biosensors, movement of electrons produced in a redox reaction is the physical reaction.

7. Heat output: calorimetric biosensor:: light output: ____________
a) Optical biosensor
b) Piezo-electric biosensor
c) Potentiometric biosensor
d) Amperometric biosensor
View Answer

Answer: a
Explanation: When the physical change accompanying the reaction is heat output, the biosensor is called as calorimetric biosensor. In the same way, when the physical change accompanying the reaction is light output or a light absorbance difference between the reactants and products, then the biosensor is referred to as optical biosensor.

8. When the physical change produced in a biosensor is due to the movement of electrons produced in a redox reaction, the biosensor is referred to as ____________
a) calorimetric biosensor
b) potentiometric biosensor
c) piezo-electric biosensor
d) amperometric biosensor
View Answer

Answer: d
Explanation: The key part of a biosensor is the transducer which makes use of a physical change accompanying the reaction. This may be as follows
• Amperometric biosensor: movement of electrons produced in a redox reaction.
• Calorimetric biosensor: the heat output (or absorbed) by the reaction.
• Potentiometric biosensor: changes in the distribution of charges causing an electrical potential to be produced.
• Optical biosensor: light output during the reaction or a light absorbance difference between the reactants and products.
• Piezo-electric biosensor: effects due to the mass of the reactants or products.

9. Distribution of charges: Potentiometric biosensor:: Mass of reactants or products: _________
a) Optical biosensor
b) Calorimetric biosensor
c) Piezo-electric biosensor
d) Amperometric biosensor
View Answer

Answer: c
Explanation: In a biosensor, when the changes in the distribution of charges causes an electrical potential to be produced. Such biosensors are referred to as potentiometric biosensor. In the same way, if the effects are due to the mass of the reactants or products, then the biosensor is referred to as piezo-electric biosensor.
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10. There are 3 so called generation of biosensors.
a) True
b) False
View Answer

Answer: a
Explanation: There are 3 so called generation of biosensors and they are as follows:
• 1st generation: The normal product of the reaction diffuses to the transducer and causes the electrical response.
• 2nd generation: Specific mediators between the reaction which generate an improved response by passing it through the transducer.
• 3rd generation: No product or mediator diffusion is directly involved. But, the reaction itself causes the response.
Hence the above statement is true.

11. _______________ biosensors are those in which the changes in the distribution of charges causing an electrical potential to be produced.
a) Calorimetric
b) Potentiometric
c) Optical
d) Amperometric
View Answer

Answer: b
Explanation: Potentiometric biosensors are those in which the changes in the distribution of charges causing an electrical potential to be produced. Calorimetric biosensors are those in which the physical change is the heat output (or absorbed) by the reaction. Optical biosensors involve light output during the reaction as a physical change. Amperometric biosensors are those which involve the movement of electrons produced in a redox reaction as a physical change given to a transducer.

12. What property of enzyme doesn’t make it an excellent analytical reagent?
a) Specificity
b) Selectivity
c) Piezo-electric biosensor
d) Location of the enzyme
View Answer

Answer: c
Explanation: Enzymes make excellent analytical reagents due to their specificity, selectivity and efficiency. Whereas as the location of enzyme is important while isolating an enzyme for its use in different ways.

13. In a biosensor ___________ is one which involves subtracting a ‘reference’ baseline signal from the sample signal.
a) signal processor
b) amplifier
c) detector
d) transducer
View Answer

Answer: a
Explanation: In a biosensor, signal processor is one that involves subtracting a ‘reference’ baseline signal from the sample signal. Transducer is one that converts the reaction data into an electrical signal. Amplifier is used to amplify the signal from the transducer as it is of low frequency. Detector is used to detect the value obtained from the whole process.
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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter