1. Proteins are made up of amino acids. These amino acids are linked together by which of the following bonds?
a) Disulfide bond
b) Hydrogen bond
c) Ionic bond
d) Peptide bond
Explanation: The amino acids in a protein are linked together by a peptide bond. The peptide bond is an amide linkage formed by the reaction of the carboxylic group of one amino acid amino group of the other amino acid.
2. The peptide bond observes which of the following characters?
a) Single bond
b) Triple bond
c) Complete double bond
d) Partial double bond
Explanation: The peptide bond is formed by the reaction of the carboxylic group of one amino acid amino group of the other amino acid. The peptide bond observes partial double bond character due to the lone pair of electrons on the nitrogen atom.
3. Which of the following phenomenon results in the partial double-bond character of the peptide bond?
a) Electronegativity
b) Both resonance and steric hindrance
c) Steric hindrance
d) Resonance
Explanation: The peptide bond observes the partial double bond character due to resonance. There is a lone pair of electrons on the nitrogen atom. These electrons resonate to give the peptide bond its partial double bond character.
4. There is a limitation to the rotation of bonds on either side of the peptide bond, due to which of the following phenomenon?
a) Hydrophobicity
b) Resonance
c) Electronegativity
d) Steric hindrance
Explanation: There is a limitation to the rotation of bonds on either side of the peptide bond, due to steric hindrance. Steric hindrance is the repulsion faced by two groups when they come too close to each other.
5. What is the span of rotation of dihedral angles?
a) 0° to 90°
b) 0° to – 180°
c) 0° to 180°
d) – 180° to 180°
Explanation: The span of rotation of dihedral anglesis – 180° to 180°. This means that there is the possibility of rotation of these angles from – 180° to 180°. But the rotation of these angles is restricted to a subset of this span due to steric hindrance.
6. There are two single bonds on either side of the peptide bond. What are the angles of rotation of these bonds known as?
a) Tetrahedral angles
b) Trihedral angles
c) Monohedral angles
d) Dihedral angles
Explanation: The angles of rotation of the bonds on either side of the peptide bond are known as dihedral angles. The span of rotation of these angles is – 180° to 180°.
7. Which of the following is also known as dihedral angles?
a) Right angles
b) Obtuse angles
c) Acute angles
d) Torsion angles
Explanation: Torsion angles are also known as dihedral angles. There are two bonds on either side of the peptide bond. The angle of rotation of these bonds is known as torsion angles.
8. Left-handed alpha-helix allowed region is present in which of the following quadrants of Ramachandran plot?
a) Fourth quadrant
b) Third quadrant
c) Second quadrant
d) First quadrant
Explanation: Ramachandran plot is the depiction of allowed and disallowed dihedral angles. There are some allowed and some disallowed regions in each quadrant. Left-handed alpha-helix allowed region is present in the first quadrant of the Ramachandran plot.
9. Beta-sheets allowed region is present in which of the following quadrants of Ramachandran plot?
a) First quadrant
b) Third quadrant
c) Fourth quadrant
d) Second quadrant
Explanation: Beta-sheets allowed region is present in the second quadrant of the Ramachandran plot. This region contains values of allowed dihedral angles such that the protein would assume a beta-sheet secondary structure.
10. Right-handed alpha-helix allowed region is present in which of the following quadrants of Ramachandran plot?
a) Fourth quadrant
b) Second quadrant
c) First quadrant
d) Third quadrant
Explanation: Right-handed alpha-helix allowed region is present in the third quadrant of the Ramachandran plot. It contains values of allowed dihedral angles such that the protein would assume a right-handed alpha-helix secondary structure.