This set of Protein Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Protein Folding – 1”.
1. Which amino acids are buried deep inside a protein structure?
a) Either hydrophobic or hydrophilic
b) Both hydrophobic and hydrophilic
c) Hydrophilic
d) Hydrophobic
View Answer
Explanation: Hydrophobic amino acids are buried deep inside a protein structure. The environmental conditions of a globular protein molecule are usually aqueous, and hence, hydrophilic. Thus, to avoid unstable interactions the hydrophobic amino acids are buried deep inside a protein structure.
2. Which of the following amino acids are likely to be present on the surface of a globular protein?
a) Both hydrophobic and hydrophilic
b) Either hydrophobic or hydrophilic
c) Hydrophobic
d) Hydrophilic
View Answer
Explanation: Hydrophilicamino acids are likely to be present on the surface of a globular protein. These hydrophilic amino acids form stable interactions with the aqueous environment when they are present on the surface of a protein. Hence, they are most likely to be present on the surface.
3. Which of the following class of proteins helps a newly made protein molecule to fold properly?
a) Mitochondrial proteins
b) Ribosomal proteins
c) Immunoglobulins
d) Chaperones
View Answer
Explanation: Chaperones are a class of proteins that help a newly made protein molecule to fold properly. Many of the newly made proteins fold properly on their own, but some require assistance in folding. These chaperones assist these proteins to fold properly.
4. To which of the special class of proteins do heat-shock proteins belong?
a) Immunoglobulins
b) Chloroplast proteins
c) Catalytic proteins
d) Chaperones
View Answer
Explanation: Heat-shock proteins belong to a special class of proteins called chaperones. These proteins are produced in large amounts in certain bacteria upon exposure to high temperatures. These proteins help bacteria thrive in the higher temperature environment.
5. Which of the following chaperones act early in the life of many proteins?
a) Hsp50
b) Hsp40
c) Hsp60
d) Hsp70
View Answer
Explanation: There are several major families of eukaryotic chaperones, including the Hsp60 and Hsp70 proteins. The Hsp70 acts early in the life of many proteins, binding to a string of amino acids before the protein leaves the ribosome.
6. To which of the following strings present on the polypeptide chain, does an Hsp70 machinery bind?
a) A string of about six hydrophobic amino acids
b) A string of about seven hydrophilic amino acids
c) A string of about six hydrophilic amino acids
d) A string of about seven hydrophobic amino acids
View Answer
Explanation: The Hsp70 chaperones act early in the life of many proteins. They bind to a string of about seven hydrophobic amino acids, even before the newly made protein leaves the ribosome.
7. The Hsp70 machinery binds to the polypeptide chain after it has left the ribosome.
a) True
b) False
View Answer
Explanation: Hsp70 proteins are a special class of proteins that assist in the folding of newly synthesized proteins. The Hsp70 chaperones act early in the life of proteins and bind to them before they leave the ribosome.
8. When the Hsp70 bound to proteins hydrolysis the ATP, it undergoes a conformational change. This change causes Hsp70 molecules to perform which of the following activities?
a) No activity at all
b) Cleave the target
c) Dissociate from target
d) Associate even more tightly to the target
View Answer
Explanation: Aided by a set of smaller Hsp70 proteins, ATP bound Hsp70 molecules to grasp their target protein and then hydrolyze ATP to ADP. This hydrolysis induces some conformational changes that cause the Hsp70 molecules to associate even more tightly with the target.
9. Which of the following event causes the dissociation of Hsp70 molecules from proteins?
a) Rapid ADP binding after ATP release
b) Slow ATP binding after ADP release
c) Slow ADP binding after ATP release
d) Rapid ATP binding after ADP release
View Answer
Explanation: Hsp70 molecules bind to the protein on seeing a hydrophobic patch of seven amino acids on the protein. Hsp40 molecules also bind and assist Hsp70 molecules. After the Hsp40 dissociates, the rapid binding of ATP induces the dissociation of Hsp70 molecules after the ADP release.
10. In reality, only one cycle of Hsp protein binding and release helps the target protein to refold.
a) True
b) False
View Answer
Explanation: In reality, repeated cycles of Hsp protein binding and release helps the target protein to refold. Hence, the above statement is false. Only a small change occurs in a single cycle and hence, many such cycles are required.
11. Which of the following phenomenon allows chaperones to recognize a wide variety of misfolded structures?
a) ATP release
b) ATP binding
c) GTP hydrolysis
d) ATP hydrolysis
View Answer
Explanation: ATP hydrolysis allows chaperones to recognize a wide variety of misfolded structures. It helps to halt any further misfolding and to recommence the folding of a protein in an orderly way.
12. Hsp60 like proteins act before the target protein leaves the ribosome.
a) True
b) False
View Answer
Explanation: Hsp60 like proteins act late in the life cycle of many proteins. They act after a protein has left the ribosome. Hence, the above statement is false. On the contrary, Hsp70 like proteins acts early in the life of many proteins.
13. Which type of chaperones form an “isolated chamber”?
a) Hsp30
b) Hsp40
c) Hsp70
d) Hsp60
View Answer
Explanation: Hsp60 like chaperones, sometimes called a chaperonin, forms an “isolatedchamber” into which misfolded proteins are fed, preventing their aggregation and providing them with a favorable environment in which to attempt to refold. Hsp60 like proteins form a large barrel-shaped structure that acts after a protein has been fully synthesized.
14. What are Hsp60 like proteins known as in the cytosol of a vertebrate cell?
a) Hsp70
b) from
c) GroEL
d) TCP 1
View Answer
Explanation: Hsp60 like proteins in the cytosol of a vertebrate cell are known as TCP 1. This type of molecular chaperones is also known as a chaperonin. These proteins are barrel-shaped.
15. What is the interval of time for which proteins are stored inside the barrel-shaped proteins?
a) 60 seconds
b) 45 seconds
c) 30 seconds
d) 15 seconds
View Answer
Explanation: The misfolded proteins are first captured inside the barrel-shaped proteins by the hydrophobic interactions. After about 15 seconds, ATP hydrolysis occurs and weakens the complex to release the proteins.
Sanfoundry Global Education & Learning Series – Protein Engineering.
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