This set of Marine Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Isolation of Marine Natural Products”.
1. Organic solvents are used to isolate bioactive compounds from marine organisms.
a) True
b) False
View Answer
Explanation: Marine organisms prove to be a great source of bioactive secondary metabolites. These compounds can be broadly separated using fractionation with organic solvents.
2. The isolation of bioactive compounds from which of the following fractions is easy?
a) Water
b) Phenol
c) Chloroform
d) Distilled water
View Answer
Explanation: After the broad separation of crude extracts of marine bioactive compounds, the compounds are separated into water soluble and water insoluble (lipophilic) fractions. Isolation of pure compounds from chloroform and hexane soluble lipophilic fractions is easier.
3. Isolation of polar bioactive compounds from marine sources is easier.
a) True
b) False
View Answer
Explanation: Isolation of non-polar bioactive compounds is easier than the separation of polar counterparts. The non-polar bioactive compounds are extracted in hexane, benzene and chloroform.
4. Which of the following is a problem associated with the isolation of polar bioactive compounds of marine origin?
a) pH
b) Temperature requirements
c) Salt content
d) Coloration of the compounds
View Answer
Explanation: The bioactive compounds that are polar and water soluble have two major problems associated with their isolation from the crude extract namely the high salt content carried over from the seawater to aqueous extracts and bacterial/ fungal growth that can degrade the active constituents of the bioactive fraction.
5. Addition of alcohols can prevent which of the following in isolation of marine polar bioactive compounds?
a) Bacterial growth
b) Fungal growth
c) Compound discoloration
d) Salt precipitation
View Answer
Explanation: Addition of small amount of alcohols or immiscible organic solvents such as n-Butanol or toluene prevents the growth of bacteria in water soluble fractions of marine bioactive compounds.
6. Boiling of organisms prior to extraction of bioactive compounds is done to ________________
a) inactivate degrading enzymes
b) activating degrading enzymes
c) permeabilizing the membrane
d) increasing water solubility
View Answer
Explanation: Boiling of marine organisms prior to extraction of bioactive compounds may be done in order to inactivate the enzymes that can reduce the former’s bioactivity, such as glycosidases, proteinases etc.
7. Which of the following is used for concentration of aqueous extracts of marine bioactive compounds?
a) Crystallization
b) Boiling
c) Freeze-drying
d) Vacuum separation
View Answer
Explanation: For concentration the aqueous extracts of marine bioactive compounds, freeze drying is used instead of evaporation (as in case of non-polar compounds). This is because sea water has high heat of vaporization and prolonged evaporation can lead to destruction of the activity of compounds.
8. Desalting is the process done to ___________________ while working with aqueous extracts from marine organisms.
a) remove inorganic salts
b) remove biomass
c) add density
d) increase temperature
View Answer
Explanation: Desalting is the process done to remove inorganic salts from the aqueous extracts of marine organisms, the presence of which interfere with bioassays and chromatographic separations.
9. Which of the following can be used to for desalting of aqueous extracts from marine organisms?
a) Methane
b) Chloform
c) Ethylene
d) Methanol
View Answer
Explanation: For desalting i.e. removing inorganic salts, from the aqueous extracts of marine organisms absolute methanol can be used. The bioactive residues are treated with absolute methanol and the solvent is removed, henceforth removing majority of the salt.
10. In which of the following separation procedures, the stationary phase is hydrophobic?
a) Reverse-phase chromatography
b) Thin-layer chromatography
c) Fluorescence activated cell sorting
d) High-performance liquid chromatography
View Answer
Explanation: In the reverse-phase chromatography, the stationary phase is hydrophobic (non-polar) and the mobile phase is polar. A combination of organic solvents such as methanol, acetonitrile etc. can be used in this process.
11. The classical method of structure determination of the marine bioactive compound requires _________________________
a) degradation of the molecule
b) vaporization of the molecule
c) fluorescence labeling
d) tagging the compound with HRP
View Answer
Explanation: After the bioactive compound of interest is isolated in its pure form the next step is to elucidate the structure of that compound. The classical approach to this requires degradation of the molecule to establish the nucleus and other transformation reactions.
12. Which of the following is used for elution, while using a strongly acidic ion-exchange resin such as Dowex-50?
a) Ethanol
b) Aqueous ammonia
c) Ammonium
d) Methane
View Answer
Explanation: Adsorption on a strongly acidic ion-exchange resin can be used for preliminary separation of the total amino acid fraction. For subsequent elution of amino acid fraction, aqueous ammonia is used, ammonia can be removed under reduced pressure at low temperature.
13. After adsorption onto a strong acid cation-exchange resin, the amino acids can be eluted using ______________________
a) linear gradient of HCl
b) linear gradient of methane
c) linear gradient of methanol
d) linear gradient of benzene
View Answer
Explanation: After adsorption onto a strong acid cation-exchange resin such as Dowex-50, the elution of amino acids can be done using dilute ammonia or a linear gradient of hydrochloric acid (HCl). For basic amino acids, acidic resins such as Dowex-50 are used.
14. Column chromatography on carbon-celite is the best method for isolation of _________________
a) amino sulfonic acids
b) peptides
c) steroids
d) terpenoids
View Answer
Explanation: Column chromatography on carbon-celite is the best method for obtaining individual components from a mixture of amino sulfonic acids. Depending upon the nature of amino acid fraction, different chromatographic separations are used.
15. The marine algae are mainly used for extracting bioactive __________________
a) peptides
b) hydrocarbons
c) inorganic metals
d) amino acids
View Answer
Explanation: Algal extracts contain amino acids and other nitrogen containing compounds in high abundance. For isolating amino acids from the marine algae, initially the algal material is homogenized with ethanol.
Sanfoundry Global Education & Learning Series – Marine Biotechnology.
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