Pharmaceutical Biotechnology Questions and Answers for Freshers on “Biopharmaceuticals – Peptide and Protein Structure Stability Profile”.
1. What is the name of the bond which is caused by changes in electron density?
a) Vander Waals force
b) H bond
c) Hydrophobic interaction
d) Electrostatic bond
Answer: a
Clarification: Van der Waals forces are also known as London forces. They are weak interactions caused by momentary changes in electron density in a molecule. They are the only attractive forces present in nonpolar compounds. The surface area of a molecule determines the strength of the van der Waals interactions between molecules.
2. Which of the following is a characteristic of the secondary structure of a protein?
a) Amino acid sequence
b) Association of secondary structure
c) Alpha helix and beta sheets
d) Association of polypeptides
Answer: c
Clarification: Secondary structure is formed by the interactions between the amino acids of a peptide chain. They are mostly alpha helix and beta sheets. Alpha-helix and b-sheet, if occur together, are found in different structural layers. Beta sheets are most stable.
3. Van der Waals forces are the only attractive forces present in nonpolar compounds.
a) True
b) False
Answer: a
Clarification: They are weak interactions caused by momentary changes in electron density in a molecule. Thus they are the only force between non-polar molecules. Such as CH4 has no net dipole, at any one instant its electron density may not be completely symmetrical, resulting in a temporary dipole. This can induce a temporary dipole in another molecule. The weak interaction of these temporary dipoles constituents’ van der Waals forces.
4. What is the name of the bond formed between two ions by the sharing of electrons?
a) Disulfide bond
b) H bond
c) Hydrophobic interaction
d) Covalent bond
Answer: d
Clarification: Covalent bond is the bond that occurs due to the sharing of electrons between the molecules. This bond can form bonds in any polyatomic ions or diatomic ions. This is one of the strongest bond and the energy required to break one such bond is 250 kJ/mol.
5. What is the name of the bond formed between two ions by the transfer of electrons?
a) Disulfide bond
b) Ionic bond
c) Hydrophobic interaction
d) Covalent bond
Answer: b
Clarification: Bond formed between two ions by the transfer of electrons. It involves electrostatic attraction between oppositely charged ions. In ionic bonds generally, a metal loses an electron becoming a positively charged ion and a nonmetal accepts that ion becoming a negatively charged ion.
6. What is the name of the bond found in metals; holds metal atoms together very strongly?
a) Disulfide bond
b) Ionic bond
c) Hydrophobic interaction
d) Metallic bond
Answer: d
Clarification: Metallic bonds are found in metals. It arises from the electrostatic attraction between electrons. When metals are bonded with proteins they are known as metalloproteins. They usually coordinate with nitrogen, oxygen, etc.
7. What is the name of the bond formed when electrons are shared equally?
a) Disulfide bond
b) Nonpolar covalent bond
c) Hydrophobic interaction
d) Metallic bond
Answer: b
Clarification: When electrons between the atoms, while bonding is shared equally, are known as non-polar covalent bonds such as H2 or Cl2. And when the electrons are shared unequally they are called polar covalent bond such as H2O.
8. What is the name of the bond formed when electrons are shared unequally?
a) Polar covalent bond
b) Nonpolar covalent bond
c) Hydrophobic interaction
d) Metallic bond
Answer: a
Clarification: A covalent bond is when a bond formed by the sharing of electrons. A nonpolar covalent n=bond is when electrons are shared equally such as H2 or Cl2. And Polar covalent bonds are where the electrons are not shared equally such as H2O.
9. Alpha-helix and b-sheet, if occur together, are found in different structural layers.
a) True
b) False
Answer: a
Clarification: There some of the rules of secondary structure and these are hydrophobic side groups must be buried inside the folds, therefore, layers must be created (b-a-b; a-a). Alpha-helix and b-sheet, if occur together, are found in different structural layers. Adjacent polypeptide segments are stacked together. The b-sheet is the most stable.
10. Adjacent polypeptide segments are stacked one above other.
a) True
b) False
Answer: b
Clarification: Adjacent polypeptide segments are stacked together is a rule of Secondary structure of proteins. Secondary structure composition will be all alpha and beta motifs together or segregated. Motifs are stable arrangements which makes a secondary structure stable. Packing side chains from adjacent secondary elements produces a super secondary structure.
11. B-Sheet is the most stable.
a) True
b) False
Answer: a
Clarification: There are some of the rules of Secondary protein structure and one of them is that the Beta sheet is the most stable. The beta sheet is a paper like structure formed mostly by the hydrogen bonds between the NH molecule and CO molecule of different amino acids.
12. Which of the following will be a characteristic of homotypic quaternary structure?
a) Formed by any single peptide chain in a whole protein molecule
b) Arrangement of polypeptide chains
c) Association between identical polypeptides
d) Association between subunits of different structure
Answer: c
Clarification: The biological function of some molecules is determined by multiple polypeptide chains. Two kinds of quaternary structures: both are multi-subunit proteins. Homotypic which is an association between identical polypeptide chains. Heterotypic which will be interactions between subunits of very different structures.
13. Intracellular protein tertiary structures mostly held together by ___________
a) Covalent forces
b) Disulfide bridges
c) Weak forces
d) Ionic bonds
Answer: c
Clarification: Tertiary structure is formed by the folding and packing of super secondary structures. It gives a globular shape. Tertiary structures are stabilized by the bonds which are mostly formed between the R groups. Protein tertiary structures are mostly held by weak forces.
14. Which of the following is a characteristic of a quaternary protein structure?
a) Formed by any single peptide chain in a whole protein molecule
b) Arrangement of polypeptide chains
c) Arrangement of different folding of the structure
d) Arrangement of the water molecules on the surface
Answer: a
Clarification: Many proteins consist of a single polypeptide chain, and are defined as monomeric proteins. Others may consist of two or more polypeptide chains that may be structurally identical or totally unrelated. The arrangement of these polypeptide subunits is called the quaternary structure of the protein.
15. What bonds stabilize the extracellular structure of proteins?
a) Hydrogen bond
b) Disulfide bonds
c) Hydrogen bonds
d) Ionic bonds
Answer: b
Clarification: Bonds that stabilize tertiary structure are: hydrogen, disulfide, ionic and hydrophobic bonds. Intracellular protein tertiary structures mostly held together by weak forces. Extracellular tertiary structures stabilized by disulfide (covalent) bonds.