Protein Engineering Question Bank on “Structure Function Relationships – Peripheral Membrane Proteins”.
1. The kinds and amounts of proteins associated with bio-membranes is same.
A. True
B. False
Answer: B
Clarification: 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 %
Answer: D
Clarification: 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 %
Answer: D
Clarification: 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
Answer: B
Clarification: 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
Answer: D
Clarification: 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
Answer: B
Clarification: 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
Answer: D
Clarification: 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
Answer: B
Clarification: 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