1. Which among the following structure of a protein describes the folding of its secondary structural elements and specifies the position of every atom in a protein, including those of side chains?
a) Primary structure
b) Secondary structure
c) Quaternary structure
d) Tertiary structure
Explanation: Tertiary structure of a protein describes the folding of its secondary structural elements and specifies the position of every atom in a protein, including those of side chains. Moreover, the tertiary structure of a protein consists of secondary structural elements that join to form motifs and domains.
2. In the tertiary structure of protein, the non-polar residues tend to occur in the protein interior and polar residues on the exterior
a) false
b) true
Explanation: Generally, a globular protein contains both polar and non-polar residues. The polar residues are present mostly on the outer surface of a protein to interact with the hydrophilic environment. The non-polar residues reside in the interior of the protein. Hence, the above statement is true.
3. Which among the following residues is most likely to be present on the surface of a protein?
a) Val
b) Leu
c) Ile
d) Arg
Explanation: Arg is most likely to be present on the surface of a protein because it is a polar residue. Generally, polar residues reside on the surface of a protein. Val, leu, and Ile are non-polar residues, hence, they are not likely to be present on the surface of a protein.
4. Which among the following residues is most likely to be present in the interior of a protein?
a) Arg
b) His
c) Asp
d) Val
Explanation: Val is most likely to be present in the interior of a protein because it is a non-polar residue. Generally, non-polar residues reside in the interior of the protein. Arg, His, and Asp are polar residues, hence, they are not likely to be present in the interior of a protein.
5. Find the odd one out.
a) Phe
b) Met
c) Leu
d) Glu
Explanation: Glu is the odd one out. Glu is a charged, polar amino acid and is, therefore, most likely to be present on the surface of a protein. Phe, Met, and leu are non-polar, thus, likely to be present in the interior of the protein.
6. Which of the following options contain only those amino acids that are likely to be present on the surface of a protein?
a) Arg, Met, Lys
b) Met, Leu, Asp
c) Lys, Leu, Val
d) Arg, Asp, Lys
Explanation: The option containing Arg, Asp, and Lys is the correct option. Due to the polar nature of Asp, Arg, and Lys, they are most likely to be present on the surface of a protein. Leu, Val, and Met are non-polar residues.
7. Which of the following options contain only those amino acids that are likely to be present in the interior of a protein?
a) Arg, Val, Met
b) Asp, Met, Phe
c) Lys, Phe, Val
d) Val, Met, Phe
Explanation: The option containing Val, Met, and Phe is the correct option. Val, Met, and Phe are all non-polar residues, hence, likely to be present in the interior of the protein. Arg, Asp, and Lys are polar residues.
8. Serine is always present on the surface of protein.
a) true
b) false
Explanation: Serine is usually present on the surface of a protein but it can also be found in the interior of the molecule. When present in the interior it is always hydrogen-bonded to neutralize the polarity. Hence, the above statement is false.
9. Which of the following is a structural database?
a) CATH
b) SCOP
c) VAST
d) PDB
Explanation: PDB is a structural database. PDB stands for Protein Data Bank. It is the repository of structural information. CATH, SCOP, and VAST are not structural databases, on the contrary, they are structural classification algorithms. PDB archive is the single worldwide repository of information about the 3D structures of large biological molecules, including proteins and nucleic acids.
10. Which among the following is not a structural database?
a) PDB
b) MMDB
c) Nucleic acid database
d) CATH
Explanation: CATH is not a structural database, but it is a structural classification algorithm. CATH provides hierarchial classification of protein domains based on their folding patterns. PDB, MMDB (Molecular Modelling Database), and Nucleic acid database are structural databases.