This set of Protein Engineering Question Bank focuses on “Structure Function Relationships – Peripheral Membrane Proteins”.
1. The kinds and amounts of proteins associated with bio-membranes is same.
a) True
b) False
View Answer
Explanation: The above statement is false. The kinds and amounts of proteins associated with bio-membranes is not same. It varies depending on the cell type and subcellular organization. Although every bio-membrane has the same basic bilayer structure, the proteins associated with a particular membrane are responsible for its distinctive activities.
2. How much percent of the mitochondrial inner membrane is protein?
a) 46 %
b) 96 %
c) 86 %
d) 76 %
View Answer
Explanation: The mitochondrial inner membrane has 76 % proteins. This percentage of proteins in the cell membrane varies from cell to cell and membrane to membrane within a cell.
3. How much percent of the myelin membrane that surrounds the nerve axons, is protein?
a) 46 %
b) 95 %
c) 27 %
d) 18 %
View Answer
Explanation: Protein constitutes to about 18 % of the myelin membrane that surrounds the nerve axons. The high phospholipid content of myelin allows it to electrically insulate the nerve from its environment.
4. Approximately a third of all yeast genes code for membrane proteins.
a) False
b) True
View Answer
Explanation: The above statement is true. Approximately a third of all yeast genes code for membrane proteins. The importance of membrane proteins is evident from this discovery. Multicellular organisms have even higher number of these genes that encode for membrane proteins.
5. Which of the following cannot be a function of membrane protein?
a) Cell to cell interaction
b) Cell adhesion
c) Intracellular transport
d) Cell division
View Answer
Explanation: Cell to cell interaction, cell adhesion, and intracellular transport are all functions of membrane proteins. Cell division is not a function of membrane proteins. Many proteins are required for cell division and they are mostly located in the cytosol and inside the nucleus.
6. The lipid bilayer presents a distinctive two-dimensional hydrophobic environment for membrane proteins.
a) False
b) True
View Answer
Explanation: The above statement is true. The lipid bilayer presents a distinctive two-dimensional hydrophobic environment for membrane proteins. Many membrane proteins contain segments that are embedded within the hydrophobic core of the phospholipid bilayer.
7. Which of the following type of proteins do not directly contact the hydrophobic core of the phospholipid bilayer?
a) Integral membrane proteins
b) Lipid-anchored proteins
c) Intrinsic proteins
d) Peripheral proteins
View Answer
Explanation: Peripheral proteinsdo not directly contact the hydrophobic core of the phospholipid bilayer. Instead, they are bound to the membrane either indirectly by interacting with integral or lipid-anchored membrane proteins or directly by interacting with lipid head groups.
8. Peripheral proteins are bound only to the cytosolic face of the plasma membrane.
a) True
b) False
View Answer
Explanation: The above statement is false. Peripheral proteins are bound not only to the cytosolic face of the plasma membrane, they are bound to exoplasmic face also. On both the sides they are attached to the membrane either directly or indirectly.
9. Cytoskeleton proteins are associated loosely with the cytosolic face of the bilayer, through which proteins?
a) Exoplasmic proteins
b) Cytosolic proteins
c) Lipid-anchored proteins
d) Peripheral proteins
View Answer
Explanation: Cytoskeleton proteins are associated loosely with the cytosolic face of the bilayer, through peripheral membrane proteins. The proteins are also known as peripheral adapter proteins.
10. The association of cellular membranes with the cytoskeleton does not help in which of the following process?
a) Cell communication
b) Determination of cell shape
c) Provide mechanical properties
d) Transcription
View Answer
Explanation: The association of cellular membranes with the cytoskeleton does not help in the process of transcription. The association of cellular membranes with the cytoskeleton help in cell communication, determination of cell shape, and provide mechanical properties.
11. Which of the following class of protein (blue colored) is shown in the figure below?
a) Integral membrane protein
b) Lipid-anchored protein
c) Intrinsic protein
d) Peripheral protein
View Answer
Explanation: The protein (blue colored) that is shown in the figure above belong to the class of peripheral membrane proteins. Peripheral membrane proteins are bound to the membrane either indirectly by interacting with integral or lipid-anchored membrane proteins or directly by interacting with lipid head groups.
12. The binding of which proteins to the cell membrane is said to be reversible?
a) Lipid-anchored proteins
b) Integral membrane proteins
c) Intrinsic proteins
d) Peripheral membrane proteins
View Answer
Explanation: The binding of peripheral membrane proteins is said to be reversible. Whereas, the binding of lipid-anchored proteins, integral membrane proteins, and intrinsic proteins are not likely to be reversible.
13. Which of the following is a peripheral membrane protein?
a) Glucose permease
b) Glycophorin
c) GPCRs
d) G proteins
View Answer
Explanation: G proteins are peripheral membrane proteins. G proteins are composed of three subunits. Glucose permease, Glycophorin, and GPCRs are integral membrane proteins.
14. Which of the following is not a peripheral membrane protein?
a) Phospholipases
b) Bcl-2
c) Signal peptidase
d) DNA polymerase
View Answer
Explanation: DNA polymeraseis not a peripheral membrane protein. In fact, it is not even a membrane protein. Phospholipases, Bcl-2 proteins, and signal peptidases are peripheral membrane protein.
15. Which of the following is not a peripheral membrane protein?
a) Cholesterol oxidases
b) Glycosyl transferases
c) Transglycosidases
d) RNA polymerases
View Answer
Explanation: RNA polymerase is not a peripheral membrane protein. Cholesterol oxidases, glycosyl transferases, and transglycosidases are peripheral membrane protein. RNA polymerases are required for the transcription process which takes place in the nucleus of eukaryotic cells.
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