Q-1. Which of not a method of protein precipitation? (AIIMS Nov 2015)
a) Salting out with metals
b) Acetone & alcohol
c) Changing pH other than iso-electric pH
d) Tri-Chloro-acetic acid
Answer: Changing pH other than iso-electric pH
Explanation:
Method of protein precipitation:
Salting out protein (Ammonium sulfate most commonly used reagent for salting out)
Organic solvents (Ethanol and acetone)
Heavy metals
Altering pH at iso-electric pH
Q-2. Precipitation of proteins is done by all these except (AIIMS May 2016)
a) Trichloro-acetate
b) Salts of heavy metals
c) Alcohol and acetone
d) Above or below the iso-electric pH
Answer: Above or below the iso-electric pH
Explanation:
See above explanation.
Q-3. Protein is purified using ammonium sulfate by (AIIMS May 2009)
a) Salting out
b) Ion exchange chromatography
c) Mass chromatography
d) Molecular size exclusion
Answer: Salting out
Explanation:
Ammonium sulfate precipitation is a method of protein purification by altering the solubility of protein.
Differential precipitation of proteins by ammonium sulfate is one of the most widely used preliminary purification procedures.
It is based on proteins having differing solubility in ammonium sulfate solutions and can result in a two- to five-fold increase in specific activity.
Q-4. In chromatography mass movements of the substances in due to: (AIIMS May 2001)
a) Diffusion
b) Electrophoresis
c) Osmosis
d) Paper chromatography
Answer: Diffusion
Explanation:
Chromatography is a method by which a mixture is separated by distributing its components between two phases. The stationary phase remains fixed in place while the mobile phase carries the components of the mixture through the medium being used.
Diffusion is a concentration driven mass transfer process in chromatography.
Q-5. Which migrates fastest on paper chromatography on methylcellulose medium? (AIIMS May 2009)
a) Ascorbic acid
b) Glycine
c) Lysine
d) Valine
Answer: Valine
Explanation:
Paper chromatography is a type of partition chromatography in which the stationary phase of the system is water permanently bound to the cellulose fibers of chromatography paper. The mobile phase is usually a relatively non-polar solvent that is allowed to migrate through the paper.
The more soluble a sample is in the non-polar mobile solvent, the greater its tendency to migrate with the mobile solvent.
The more soluble a sample is in water, the greater its tendency to remain stationary in the aqueous phase. Thus, the degree of separation ultimately depends on differences in solubility of each component in water versus non-polar solvent.
Valine is most non polar amino acid among options.
Q-6. Same charged two proteins separation is done by
a) Agarose
b) DEAE Cellulose
c) Sephadex
d) None
Answer: Sephadex
Explanation:
Size exclusion chromatography or Gel filtration chromatography separates proteins based on their Stokes radius, the diameter of the sphere they occupy as they tumble in solution.
The Stokes radius is a function of molecular mass and shape.
Important point:
Sephadex is cross-linked dextran gel used for gel filtration chromatography.
Molecular separation of two proteins with same charge can be done by gel filtration chromatography. Gel filtration chromatography is the best method to differentiate proteins.
Q-7. The following separation technique depends on the molecular size of the protein (AIIMS Nov 2002)
a) Chromatography on a carboxy-methyl (CM) cellulose column)
b) Iso-electric focusing
c) Gel filtration chromatography
d) Chromatography on a diethylaminoethyl (DEAE) cellulose column.
Answer: Gel filtration chromatography
Explanation:
See above explanation.
Q-8. Molecular separation of two proteins with same charge can be done by
a) Ion exchange chromatography
b) Dialysis
c) Gel diffusion chromatography
d) Electrophoresis
Answer: Gel diffusion chromatography
Explanation:
See above explanation.
Q-9. The best method to differentiate proteins is by
a) Gel chromatography
b) Affinity chromatography
c) Ion exchange electrophoresis
d) One of the above
Answer: Gel chromatography
Explanation:
See above explanation.
Q-10. Method of chromatography in which molecules that are negatively charged are selectively released form stationary phase into the positively charged molecules in mobile phase is termed as:
a) Affinity chromatography
b) Ion – Exchange chromatography
c) Absorption chromatography
d) Size-Exclusion chromatography
Answer: Ion – Exchange chromatography
Explanation:
Ion-exchange chromatography separates ions and polar molecules based on their affinity to the ion exchanger.
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Q-11. In which type of chromatography, the proteins are bound to another substance (AIIMS May 2001)
a) Hydrophobic chromatography
b) Affinity chromatography
c) Paper chromatography
d) Gel chromatography
Answer: Affinity chromatography
Explanation:
Affinity chromatography exploits the high selectivity of most proteins for their ligands.
Enzymes may be purified by affinity chromatography using immobilized substrates, products, coenzymes, or inhibitors. In theory, only proteins that interact with the immobilized ligand adhere.
Bound proteins are then eluted either by competition with soluble ligand or, less selectively, by disrupting protein-ligand interactions using urea, guanidine hydrochloride, mildly acidic pH, or high salt concentrations.
Q-12. Hemoglobin electrophoresis is based on
a) Molecular weight
b) Charge
c) Solubility
d) Calorimetric properties
Answer: Charge
Explanation:
Electrophoresis separates charged bio-molecules based on the rates at which they migrate in an applied electrical field.
Q-13. Proteins are separated on the basis of size by
a) SDS- PAGE
b) HPLC
c) Affinity Chromatography
d) Ion exchange Chromatography
Answer: SDS- PAGE
Explanation:
The most widely used method for determining the purity of a protein is SDS-PAGE (Poly-acryl-amide gel-electrophoresis) in the presence of the anionic detergent sodium dodecyl sulfate (SDS).
Electrophoresis separates charged bio-molecules based on the rates at which they migrate in an applied electrical field.
Since the charge-to-mass ratio of each SDS polypeptide complex is approximately equal, the physical resistance each peptide encounters as it moves through the acryl-amide matrix determines the rate of migration.
Since large complexes encounter greater resistance, polypeptides separate based on their relative molecular mass (M), Individual polypeptides trapped in the acryl-amide gel are visualized by staining with dyes such as Coomassie blue.
Q-14. Separation of proteins based on size is done by
a) Affinity chromatography depending on charge
b) SDS Poly-acryl-amide gel electrophoresis
c) Ion exchange chromatography
d) High performance liquid chromatography
e) Electrophoresis
Answer: SDS Poly-acryl-amide gel electrophoresis
Explanation:
See above explanation.
Q-15. The molecular weight of a protein can be determined by (AIIMS Nov 2004)
a) Native Poly Acryl-amide Gel Electrophoresis (PAGE)
b) Sodium Dodecyl Sulphate PAGE
c) Iso-electric focusing
d) Ion Exchange Chromatography
Answer: Sodium Dodecyl Sulphate PAGE
Explanation:
See above explanation.
Q-16. A protein with molecular weight of 100 kD is subjected to SDS PAGE electrophoresis. The SDS PAGE electrophoreses pattern show two widely separated bands of 20 kD and 30kd after addition of mercapto-ethanol. The true statement regarding this will be
a) The protein has undergone complete lysis
b) The protein is a monomer of 20 kD and 30 kD protein
c) The protein is a dimer of two 20 kD and 30 kD protein
d) The protein is a tetramer of 20 kD and 30 kD proteins
Answer: The protein is a dimer of two 20 kD and 30 kD protein
Explanation:
The protein is a dimer of two 20 kD and 30 kD> 2X 20 + 2X30 = 100 kD
Q-17. Electrophoresis done under pH gradient is
a) Iso-osmotic
b) Iso-electric
c) Ion exchange
d) None
Answer: Iso-electric
Explanation:
Iso-electric focusing (IEF):
Ionic buffers called ampholytes and an applied electric field are used to generate a pH gradient within a poly-acryl-amide matrix.
Applied proteins migrate until they reach the region of the matrix where the pH matches their iso-electric point (pI), the pH at which a molecule’s net charge is zero.
IEF is used in conjunction with SDS-PAGE for two-dimensional electrophoresis. It separates polypeptides, based on pI in one dimension and based on Mr in second.
Q-18. Protein purification and separation can be done by all except
a) Chromatography
b) Centrifugation
c) Electrophoresis
d) Densitometry
Answer: Densitometry
Explanation:
Protein purification and separation can be done by:
Precipitation of proteins with ammonium sulfate (Salt fractionation)
Chromatography
Electrophoresis
Ultracentrifugation
Important point:
Densitometry may be used as a method to quantitate protein in tissue.
Q-19. Proteins can be separated by the following except
a) Electrophoresis
b) Ultra centrifugation
c) Gas chromatography
d) Salt separation
Answer: None
Explanation:
Techniques for protein separation:
Chromatography
Electrophoresis
Ultracentrifugation
Salting out with ammonia sulfate
Q-20. Molecular size is assessed by
a) Sedimentation
b) Absorption mass spectroscopy
c) Lyophilisation
d) Salting out
Answer: Absorption mass spectroscopy
Explanation:
Mass spectrometry (MS) has replaced the Edman technique as the principal method for determining the sequences of peptides and proteins.
Conventional mass spectrometers generally are used to determine the masses of molecules of 4000 Da or less, whereas time-of-flight mass spectrometers are suited for determining the large masses of proteins.
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Q-21. The substance present in the gall bladder stones or the kidney stones can be best identified by the following techniques
a) Fluorescence spectroscopy
b) Electron microscopy
c) Nuclear magnetic resonance
d) X-ray diffraction
Answer: X-ray diffraction
Explanation:
Techniques for analysis of renal and gall bladder stones:
Infrared spectroscopy
Polarizing microscopy
X-ray diffraction
Q-22. Nephelometry is based on the principle of: (AIIMS Nov 2007)
a) Light attenuated in intensity by scattering
b) Reduced transmission of light
c) Refraction of light
d) Filtration of solutes by kidney
Answer: Light attenuated in intensity by scattering
Explanation:
Turbidimetry is the measurement of the degree of attenuation of a radiant beam incident on particles suspended in a medium, the measurement being made in the directly transmitted beam.
Nephelometry is the measurement of the light scattered by suspended particles, the measurement usually being made perpendicularly to the incident beam.
(Ref: http://apps.who.int/phint/en/p/docf/)
Q-23. All of the following can determine the protein structure except (AIIMS Nov 2008)
a) Mass spectrometry
b) NMR spectrometry
c) High Performance Liquid Chromatography
d) X-Ray crystallography
Answer: High Performance Liquid Chromatography
Explanation:
High Performance Liquid Chromatography (HFLC) is used to separate, identify, and purify compound.
Methods for determining bio-molecular structures:
NMR spectroscopy
Mass spectrometry
X-Ray crystallography
Specific sequencing methods
Q-24. Which technique is used to detect microscopic structure of bio-molecule?
a) Agar gel electrophoresis
b) X-Ray crystallography
c) MRI
d) Ion exchange chromatography
Answer: X-Ray crystallography
Explanation:
X-ray crystallography is a tool used for identifying the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays to diffract into many specific directions.
The method also reveals the structure and function of many biological molecules, including vitamins, drugs, proteins and nucleic acids such as DNA.
Q-25. Study of multiplication of proteins in disease process is called
a) Proteomics
b) Genomics
c) Glycomics
d) Nucleomics
Answer: Proteomics
Explanation:
Proteomics aims to identify the entire complement of proteins elaborated by a cell under diverse conditions.
Proteomics aims to identify the entire complement of proteins elaborated by a cell under diverse conditions.
Important point:
The proteome is the entire set of proteins expressed by a genome, cell, tissue, or organism at a certain time.