1. Which of the following proteins help in the refolding of proteins in Endoplasmic Reticulum?
a) TCP 1
b) GroES
c) GroEL
d) BIP
Explanation: BIP is the special class of proteins that help in the refolding of proteins in Endoplasmic Reticulum. GroES and GroEL are found in bacterial cells. TCP 1 is found in the cytosol of vertebrate cells.
2. What are the Hsp60 like proteins called in bacterial cells?
a) BIP
b) TCP 1
c) GroES
d) GroEL
Explanation: Hsp60 like proteins in bacterial cells are called as GroEL. GroES is a cap of these GroEL proteins. TCP 1 is not found in bacterial cells; it is found in vertebrate cells. BIP is usually found in the endoplasmic reticulum.
3. Which of the following does not lead to exposure of hydrophobic amino acids on the surface of a protein?
a) Failed to fold correctly
b) Protein suffered an accident
c) Failed to find its normal partner subunit
d) Proper folding of proteins
Explanation: The events that can lead to exposure of hydrophobic amino acids on the surface of a protein are failing to fold correctly, suffered an accident, and failing to find normal partner subunit. Whereas, proper folding of proteins does not lead toexposure of hydrophobic amino acids on the surface.
4. A misfolded protein or a protein with the abnormally exposed hydrophobic region is not merely useless to the cell, they can be dangerous.
a) false
b) true
Explanation: The above statement is true. A misfolded protein or a protein with the abnormally exposed hydrophobic region is not merely useless to the cell, they can be dangerous. They can form aggregates that are harmful to the cell.
5. What is the fate of misfolded proteins when attempts to refold it fail?
a) Sent back to the ribosome
b) Stored in vacuole
c) Kept in the cytosol
d) Destroyed by proteolysis
Explanation: When the attempts to refold, a misfolded protein fails it is destroyed. This is necessary because a misfolded or protein with exposed hydrophobic regions is not only useless to the cell, it can be dangerous to the cell.
6. Which of the following is a complex protease, used to destroy protein molecules?
a) Ubiquitin
b) Chaperone
c) Proteosome
d) Proteasome
Explanation: Proteasome is a complex protease which is used to destroy all misfolded proteins. The destruction of the misfolded protein is initiated when attempts to refold it fails. Ubiquitin is a protein that marks the protein for destruction.
7. Which of the following event increases the diameter of the barrel (Hsp60)?
a) Binding of only cap protein
b) Binding of the only ATP
c) Hydrolysis of ATP
d) Binding of ATP and a protein cap
Explanation: Binding of ATP and a protein cap increases the diameter of the barrel (Hsp60). This increase in diameter gives proteins an extra space to refold correctly.
8. Which of the following is the protein Cap of barrel-shaped bacterial Hsp60 like proteins?
a) BIP
b) TCP 1
c) GroEL
d) GroES
Explanation: GroES is the protein Cap of barrel-shaped bacterial Hsp60 like proteins. It covers the opening through which the misfolded proteins enter GroEL. Binding of GroES along with ATP increases the diameter of the barrel.
9. Which of the following is not a model for the refolding of misfolded proteins?
a) Passive model
b) Active model
c) Iterative model
d) Intermediate model
Explanation: The passive model, active model, and iterative model are models for the refolding of misfolded proteins. The intermediate model is not a model for the refolding of a misfolded protein.
10. Which of the following feature is pertaining to the passive model of the refolding of proteins?
a) Both ATP and GTP are required
b) GTP hydrolysis
c) ATP hydrolysis
d) No energy expenditure
Explanation: In the passive model there is no energy expenditure, hence, there is no ATP/GTP hydrolysis. In this model, proteins are fed in a small cage-like environment so that the proteins can attempt to refold.