This set of Bioseparation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Biological Material Properties – Light Absorption and Fluorescence”.
1. The molecule which form coloured solutions usually absorb __________
a) Visible light
b) UV light
c) Invisible light
d) X ray
View Answer
Explanation: The visible light is absorbed by the molecules which form coloured solutions. The visible light wavelength ranges between 400nm to 700nm, red light of visible light has long wavelength of 700nm and blue light has short wavelength of 400nm.
2. The protein in aqueous solution absorbs ___________
a) Visible light
b) UV light
c) Invisible light
d) X ray
View Answer
Explanation: The protein absorbs ultra violet light because of the presence of amino acid tyrosine and tryptophan. These amino acids are aromatic compounds which absorb UV light, both the amino acids have distinct absorption wavelength as well as distinct emission wavelength and has different quantum yield.
3. The wavelength at which proteins absorbs UV light is ___________
a) 254nm
b) 595nm
c) 280nm
d) 275nm
View Answer
Explanation: The proteins absorb UV light at 280nm because of the aromatic rings in the amino acids tyrosine and tryptophan.
4. The wavelength at which DNA absorbs UV light is ___________
a) 595nm
b) 280nm
c) 275nm
d) 260nm
View Answer
Explanation: The DNA absorbs UV light at 260nm wavelength due to the presence of heterocyclic acid of nucleotide. The process of absorption of light in DNA increases due to hyperchromic shift and it is caused by the purine and pyrimidine bases of DNA.
5. Light absorption is a basis of separation.
a) True
b) False
View Answer
Explanation: Light absorption is not a basis of separation; it’s just a parameter to monitor the compounds during a process of separation. In the process of liquid chromatography, the retention time of the separated components leaving the column is determined by the measurement of the absorption of light.
6. Which methods of chromatography utilize the process of light absorption?
a) Fluorimetry
b) Laminar Air Flow
c) Spectrophotometry
d) SEM
View Answer
Explanation: The spectrophotometry is used to measure the amount of light intensity absorbed when a beam of light passes through the sample. The compounds absorb and transmit range of wavelengths.
7. How much light will be absorbed by a solution when the concentration of solute 2 kg/m3 and the path length of the light within the solute is 5m? Given: (specific absorption = 1.5 A U m2/Kg).
a) 5AU
b) 20AU
c) 10AU
d) 15AU
View Answer
Explanation: The amount of light absorbed can be calculated according to the Beer-Lambert Law, A = α.C.l where, α is the specific absorbance, C is the concentration and l is the path length. Therefore, amount of light absorbed (A) = 15 A U.
8. What will be % transmittance of the absorbed light when the intensity of incident light is 4 W/m2 and it is transmitted with the intensity of 2 W/m2?
a) 100%
b) 50%
c) 75%
d) 25%
View Answer
Explanation: %T = (\(\frac{Transmitted \,light}{Incident \,light}\)) * 100, so %T = \(\frac{2 W/m2}{4 W/m2}\) * 100 = 50 %. Therefore, the % of light transmitted is 50% of the light absorbed.
9. The compounds which emits light after absorbing the light of higher frequency are ___________
a) absorbing compounds
b) transmitting compounds
c) soluble compounds
d) fluorescent compounds
View Answer
Explanation: The fluorescent compounds emit light after absorbing the light of higher intensity. The molecules of the compound get excited when an incident light of higher frequency is absorbed and it posses deactivation channel which leads to the emission of light.
10. Fluorescence is a basis of separation.
a) False
b) True
View Answer
Explanation: Fluorescence is not a basis of separation, it is one of the important parameters which help to monitor the compounds which are separated during the separation processes. It helps in determining the concentration and purity of the compounds.
11. Which method of separation utilizes the process of fluorescence?
a) Fluorimetry
b) Laminar Air Flow
c) Spectrophotometry
d) SEM
View Answer
Explanation: Fluorimetry is the method which utilizes the use of fluorescence. Example of Fluorimetry is fluorometer in which the analysis of fluorescence is performed by knowing the intensity and the wavelength of the compounds emitting the absorbed light after the excitation.
12. What are the examples of fluorescent compounds?
a) Sugar, vitamin
b) Proteins, nucleic acid
c) Protein, sugar
d) Minerals, nucleic acid
View Answer
Explanation: Proteins and nucleic acids emit light which they absorb from the incident light at 260nm and 280nm respectively. The covalent bonding and the presence of aromatic groups in nucleic acid as well as proteins make these compounds a fluorochrome i.e. the substance which emits light.
13. What is the angle of measurement of emitted light in fluorometer?
a) 45°
b) 90°
c) 120°
d) 180°
View Answer
Explanation: The emitted light is measure at an angle of 90° i.e. right angle of the incident light in order to avoid the interference of the absorbed light with the transmitted light.
14. Which separation techniques involve the use of Fluorimetry?
a) Electrophoresis
b) Filtration
c) Adsorption
d) Immunoassay
View Answer
Explanation: Immunoassay involves the use of Fluorimetry in order to measure the amount of compounds or proteins through utilization of antigen or antibody.
Sanfoundry Global Education & Learning Series – Bioseparation Technology.
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