Enzyme Technology Questions and Answers – Continuous, Discontinuous and Coupled Assay

This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “Continuous, Discontinuous and Coupled Assay”.

1. In which of the following assays, there is a “stop and sample” procedure?
a) Continuous assay
b) Coupled assay
c) Enzymatic assay technique
d) Discontinuous assay
View Answer

Answer: d
Explanation: In discontinuous assay, there is a “stop and sample” procedure which is used. Hence the name. This means that taking the sample out at required time and stopping the enzymatic activity and then measuring the amount of product. This procedure has a disadvantage of sampling errors and estimation of product. But this can be corrected by use of ion-exchange chromatography.
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2. Which of the following is not a step involved in discontinuous assay?
a) Taking sample from the reaction mixture at known time
b) Stopping the reaction by inactivating the enzyme
c) Measure the convenient change in absorbance
d) Measuring the amount of product formed
View Answer

Answer: c
Explanation: “Measure the convenient change in absorbance.” This step is involved in continuous assay, and not discontinuous, which has “stop and sample procedure”. The steps involved in discontinuous assay are as follows:
• Taking sample from the reaction mixture at known time after addition of enzyme.
• Stopping the reaction by addition of acid to inactivate the enzyme.
• Measuring the amount of product formed.

3. Which type of assay does the following reaction represent?
enzyme-technology-questions-answers-continuous-discontinuous-coupled-assay-q3
a) Continuous assay
b) Coupled assay
c) Enzymatic assay technique
d) Discontinuous assay
View Answer

Answer: a
Explanation: The above equation represents continuous assay, which involves some changes in property during the course of the reaction. In this reaction, there are changes that occur when the production glucose-6-phosphate is coupled to reduction of NADP+ to NADPH using enzyme glucose-6-phosphate dehydrogenase.

4. Which of the following assays, there is a convenient change is absorbance?
a) Continuous assay
b) Coupled assay
c) Enzymatic assay technique
d) Discontinuous assay
View Answer

Answer: a
Explanation: In continuous assays, convenient change in absorbance is seen. Discontinuous assay is one which has a “stop and sample procedure. Coupled assays are those which involve coupling of enzyme and substrate such that coupling reaction is not limiting one. Enzymatic assay technique are the procedures used to measure the amount of substrate or product in all the 3 types of assays.
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5. The reaction catalyzed by ornithine decarboxylase is an example of which assay?
a) Continuous assay
b) Coupled assay
c) Enzymatic assay technique
d) Discontinuous assay
View Answer

Answer: b
Explanation: The reaction catalyzed by ornithine decarboxylase is an example of coupled assay. In this assay, L-[1-C14] ornithine is used which liberates radioactive CO2 which can be trapped by a suitable base such as ethanolamine dissolved in 2-methoxyethanol. Then the radioactivity is measured by scintillation counting.

6. Which of the following precautions must not be followed while performing assays?
a) The substrates, buffers etc., should be of high purity
b) Enzyme preparation should as pure as possible
c) The probe must be tiny and biocompatible
d) Stability of the enzyme during the time taken by assay
View Answer

Answer: c
Explanation: “The probe must be tiny and biocompatible.” This is feature of biosensor, and not precautions to be followed. Following are the precautions that must not be followed while performing assays:
• The substrates, buffers etc., should be of high purity as the contaminants may affect the activity of the enzyme. For example: Certain NAD+ preparations contain inhibitor of dehydrogenases.
• Enzyme preparation should as pure as possible so that any other compounds or enzyme will not interfere with assay
• Stability of the enzyme during the time taken by assay to complete the reaction.
• pH, temperature etc., affects the activity of the enzyme, and hence has to be maintained by use of buffers, thermostable bath etc.
• It should be ensured that once steady state is reached, the rate of reaction is constant over a period of interest and proportional to the amount of enzyme added.

7. Which of the following is a precaution which must be followed while performing assays?
a) It should be ensured that once steady state is reached, the rate of reaction is constant over a period of interest and proportional to the amount of enzyme added
b) The response should be accurate, reproducible, precise, linear and free from electrical noise
c) The probe must be tiny and biocompatible
d) It should be cheap, small portable and capable of being used by semi-skilled operators
View Answer

Answer: a
Explanation: The precaution to be taken while performing assay is “it should be ensured that once steady state is reached, the rate of reaction is constant over a period of interest and proportional to the amount of enzyme added.” Following are the beneficial features of biosensor:
• The response should be accurate, reproducible, precise, linear and free from electrical noise.
• The probe must be tiny and biocompatible.
• It should be cheap, small portable and capable of being used by semi-skilled operators.
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8. Use of thermostable baths, buffers are necessary while performing assays.
a) True
b) False
View Answer

Answer: a
Explanation: The enzyme activity is affected by changes in temperature, pH, etc. To ensure that these parameters are stabilized, use of thermostable bath, buffer becomes necessary. Hence the above statement is true.

Sanfoundry Global Education & Learning Series – Enzyme Technology.

To practice all areas of Enzyme Technology, here is complete set of 1000+ Multiple Choice Questions and Answers.

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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