This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Working with Proteins”.
1. The salt which produces salting out effect during extraction of proteins is?
a) NH4 SO4
b) (NH4)2 SO4
c) (NH4)3 SO4
d) NaCl
View Answer
Explanation: (NH4)2 SO4 is added in the right amount can selectively precipitate some proteins, while others remain in the solution. (NH4)2 SO4 is often used for this purpose because of its high solubility in water.
2. Mobile phase can be ___________
a) Only solid
b) Only gas
c) Solid or liquid
d) Liquid or gas
View Answer
Explanation: Only liquids and gases can flow through to act as a mobile phase.
3. The pattern on paper in chromatography is called __________
a) Chroming
b) Chroma
c) Chromatograph
d) Chromatogram
View Answer
Explanation: In paper chromatography usually stationary phase is a strip of chromatography paper which is also called a chromatogram.
4. Which of the following statements about column chromatography is correct?
a) Resolution increases as the length of the column increases
b) Mobile phase is a porous solid material with appropriate chemical properties held in the column
c) Stationary phase is a buffered solution that percolates through mobile phase
d) Large proteins emerge from the column sooner than small ones
View Answer
Explanation: As the length of the column increases, the overall protein band widens as it moves through the column. Individual proteins gradually separate from each other forming bands within the broader protein and this separation increases as the length of the column increases.
5. Which of the following statements is true about size-exclusion chromatography?
a) During the separation of a mixture of proteins, protein with smallest molecular weight is eluted first
b) During the separation of a mixture of proteins, protein with largest molecular weight is eluted first
c) During the separation of a mixture of proteins, protein with largest molecular weight is eluted last
d) During the separation of a mixture of proteins, protein with largest molecular weight flow around the beads
View Answer
Explanation: Larger proteins migrate faster than the smaller ones because they are too large to enter the pores in the beads.
6. Which of the following statements is true about affinity chromatography?
a) During the separation of a mixture of proteins, the protein which does not bind to ligand is eluted first
b) During the separation of a mixture of proteins, the protein which does not bind to ligand is eluted last
c) During the separation of a mixture of proteins, the protein which binds to ligand is eluted first
d) Unwanted proteins are eluted by ligand solution
View Answer
Explanation: After proteins that do not bind to the ligand are washed through the column, the bound protein of particular interest is eluted.
7. Which of the following statements is true about ion-exchange chromatography?
a) It separates proteins according to their size
b) The column matrix with bound anionic groups is called cationic exchanger
c) The column matrix with bound anionic groups is called anionic exchanger
d) The column matrix with bound cationic groups is called cationic exchanger
View Answer
Explanation: It involves the attachment to the column matrix of ionic groups known that bind to the anted protein.
Cationic exchanger exchanges cations with anionic groups.
8. Which of the following statements is true about SDS polyacrylamide chromatography?
a) SDS polyacrylamide gel electrophoresis separates proteins on the basis of size
b) SDS polyacrylamide gel electrophoresis separates proteins on the basis of charge
c) SDS binds to proteins non-covalently with a stoichiometry of around one SDS molecule per three amino acids
d) SDS binds to proteins non-covalently with a stoichiometry of around one SDS molecule per one amino acid
View Answer
Explanation: SDS polyacrylamide gel electrophoresis separates proteins on the basis of their size or mass. SDS binds to proteins non-covalently with a stoichiometry of around one SDS molecule per two amino acids.
9. Which of the following statements is true about two-dimensional electrophoresis?
a) Separates proteins of identical molecular weight, same pI but different charge
b) Separates proteins of different molecular weight and different pI
c) Separates proteins of identical molecular weight that differ in pI
d) Isoelectric focusing is also termed as two-dimensional electrophoresis
View Answer
Explanation: SDS gel electrophoresis and isoelectric focusing together make up the process of two-dimensional electrophoresis. It separates proteins of identical molecular weight that differ in pI, or proteins with similar pI values but different molecular weights.
10. Which of the following statements is false?
a) The term activity refers to the total units of enzyme in a solution
b) The specific activity is a measure of enzyme purity
c) Specific activity increases during purification of an enzyme and becomes maximal and constant when the enzyme is pure
d) Specific activity decreases during purification of an enzyme and becomes maximal and constant when the enzyme is pure
View Answer
Explanation: The statement “Specific activity decreases during purification of an enzyme and becomes maximal and constant when the enzyme is pure” is false. In reality, specific activity increases during purification, and it reaches a maximal and constant value when the enzyme is pure.
Sanfoundry Global Education & Learning Series – Biochemistry.
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