This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Determinants of Protein Structure”.
1. Which one of the following forces will not determine the protein structure?
a) H bonds
b) Disulfide bridges
c) Spring forces
d) Dispersion forces
View Answer
Explanation: The different forces involved in the formation of proteins are hydrophobic/hydrophilic forces, H bonding, Vander Walls/dispersion forces, Electrostatic forces and disulfide bridges. These forces help proteins to attain a specific stable structure which can later perform a certain biological function.
2. Which one of the following oligopeptides gets exposed to the solvent side of the membrane protein?
a) Gln-Tyr-Glu-Arg-His-Asp-Ser-Thr-Trp-Lys-Asn
b) Ala-Leu-Met-Phe-Pro-Ile-Gln-Tyr-Glu-Arg-His
c) Ser-Thr-Trp-Lys-Asn-Ala-Leu-Met
d) Val-Ala-Leu-Met-Phe-Pro-Ile
View Answer
Explanation: The side chain of proteins having hydrophilic amino acids face towards the solvent or water when they are a part of membrane proteins or submerged proteins. The hydrophilic amino acids are Glutamine, Tyrosine, Glutamate, Arginine, Histidine, Aspartate, Serine, Threonine, Tryptophan, Lysine, Asparagine.
3. The surface of a protein in a cell is ________
a) Always polar
b) Always Non-Polar
c) Depends on its function
d) Can’t predict
View Answer
Explanation: Most of the proteins have polar groups on its surface. But it is not possible to assume all the proteins have polar groups on the surface since there are several proteins like enzymes. In enzymes, the portion of its surface that binds to the substrate will be Non-Polar whereas rest of the portion will be polar. Hence it entirely depends on its function.
4. In proteins, H-bonds are not formed when ________
a) Hydrogen is shared between N and O
b) Hydrogen is shared between N and N
c) Hydrogen is shared between O and O
d) Hydrogen is shared between N and C
View Answer
Explanation: When hydrogen is shared between two partially charged atoms, hydrogen bonds are formed. In proteins, hydrogen is shared between nitrogen and nitrogen, nitrogen and oxygen, oxygen and oxygen.
5. Hydrogen is essential for a protein to form _________
a) Primary structure
b) Primary and secondary structure
c) Secondary and tertiary structure
d) Primary, secondary and tertiary structure
View Answer
Explanation: The primary structure is stabilized by covalent bond rather than the hydrogen bonds. But in secondary and tertiary structure hydrogen play a very important role in forming super secondary structures.
6. The main function of hydrogen bonds in alpha helix is _________
a) Stabilizing the backbone
b) Donating hydrogen to the hydroxyl group of water
c) Altering its conformation
d) Inducing pucker
View Answer
Explanation: In beta sheets and alpha helixes the hydrogen is shared between non-adjacent or distant amino acids. Hydrogen bonds are the one which bends the oligopeptide into ribbon-like shape.
7. Hydrogen bonds are formed only on the surface.
a) True
b) False
View Answer
Explanation: Hydrogen bonds are not only formed on the surface but also, they are formed inside the protein at the centre stabilizing the hydrophobic groups hiding in the core.
8. Which one of the following forces is not a Van der Waal’s force?
a) Dispersion forces
b) Hydrogen bonds
c) Ionic interactions
d) Dipole-dipole forces
View Answer
Explanation: Ionic interactions do not belong to Van der Waal’s forces even though they are weak in nature. In ionic interactions, we can not find the internal division of charges.
9. What causes Van der Waal’s forces?
a) Partial distribution of atoms
b) Difference in charges
c) Fluctuation in positions of atoms
d) Sharing of nitrogen
View Answer
Explanation: Here, the electrons inside an atom gets grouped together on one side and interacts with each other. This even contributes to the positioning of functional groups of the amino acids in proteins.
10. Van der Waal’s forces are ________ times stronger than peptide bonds.
a) 1000
b) 100
c) 1/100
d) 1/1000
View Answer
Explanation: In covalent bonds, the bond is formed by the sharing of electrons between the atoms and they will be in physical contact whereas groups undergoing Van der Waal’s interactions will be just close to each other making it much weaker than covalent bonds.
11. Choose the correct combination.
a) Atom 1 having negative charges on the left side and atom 2 having positive charges on the right side, repulses
b) Atom 1 having positive charges on the left side and atom 2 having positive charges on the right side, attracts
c) Atom 1 having negative charges on the left side and atom 2 having negative charges on the right side, repulses
d) Atom 1 having negative charges on the left side and atom 2 having positive charges on the right side, repulses
View Answer
Explanation: Since atom 1 has exactly the opposite charge to that of atom 2 at the interaction region, atom 1 attracts atom 2.
12. Van der Waal’s stabilize the Enzyme-Ligand interactions.
a) True
b) False
View Answer
Explanation: Enzyme-Ligand interactions are stabilized by the dipole-dipole interactions between the side chains of amino acids of proteins. The charged side chains undergo Van der Waal’s interactions.
13. Disulfide bonds are _______ bonds.
a) Peptide bonds
b) Covalent bonds
c) Ionic bond
d) London dispersion
View Answer
Explanation: These are strong bonds are formed when the sulphur containing amino acids like methionine, cysteine, taurine and homocysteine get oxidized and form sulphur-sulphur bonds between non-adjacent amino acids.
14. Disulfide bridges are mainly involved in _________
a) Primary and secondary structure
b) Secondary and tertiary structure
c) Tertiary and quaternary structure
d) Secondary, tertiary and quaternary structure
View Answer
Explanation: Primary structure of a protein is just a linear chain. Secondary structure can be a helix or a sheet. In both of these cases, the structure is stabilized only by peptide and H-bonds. Disulfide bridges come into picture only when tertiary and quaternary structure form.
Sanfoundry Global Education & Learning Series – Structural Biology.
To practice all areas of Structural Biology, here is complete set of Multiple Choice Questions and Answers.
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