This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Quaternary Structure of Proteins”.
1. Quaternary structure of proteins is the three-dimensional arrangement of protein subunits.
a) True
b) False
View Answer
Explanation: Not all proteins are constituted of single polypeptide chains. Some contain two or more than two polypeptide chains, which may not necessarily be identical. The arrangement of these chains in the three-dimensional space is called the quaternary structure of the protein.
2. The higher levels of protein structure are classified into ________
a) Fibrous proteins and globular proteins
b) Fibrous proteins and immuno-proteins
c) Globular proteins and immuno-proteins
d) Structural proteins and immuno-proteins
View Answer
Explanation: Fibrous proteins consist of long strands or sheets of the polypeptide chains while polypeptides folded into a compact, spherical and globular shape are called globular proteins.
3. Which of the following are the basic functions of a fibrous protein?
a) Enzymatic, regulatory functions
b) Provide shape, support, external protection
c) Fight foreign antigens
d) Only provide structural support
View Answer
Explanation: Fibrous proteins are mainly found in systems that provide shape and support like collagen and keratin while regulatory functions are taken care of by globular proteins like myoglobin.
4. Which one of the following is the elementary structural unit of a fibrous protein?
a) Primary structural protein
b) Secondary structural protein
c) Tertiary structural protein
d) Quaternary structural protein
View Answer
Explanation: A fibrous protein is built by repeating units of the secondary structure of the protein as a fibrous protein is a quaternary structural protein and a quaternary structure is the three dimensional arrangement of protein subunits, which in the case of a fibrous protein is the arrangement of the secondary structural proteins.
5. The reason for insolubility of fibrous proteins in water is _______
a) High concentration of hydrophilic amino acid residues in the interior and on surface of the protein
b) Low concentration of hydrophilic amino acid residues in the interior and on surface of the protein
c) High concentration of hydrophobic amino acid residues in the interior and on surface of the protein
d) Low concentration of hydrophobic amino acid residues in the interior and on the surface of the protein
View Answer
Explanation: Due to the large number of hydrophobic amino acid residues on the surface and in the interior of the protein, similar polypeptide chains are buried, packed together forming supramolecular complexes which is the reason for insolubility in water.
6. Secondary structures of fibrous proteins are alpha helix, beta confirmation, collagen triple helix.
a) True
b) False
View Answer
Explanation: The above are responsible for flexibility and insoluble protection in hair, flexible filaments found in silk fibroin and high tensile strength in bone matrix.
7. What facilitates structural diversity to globular proteins to carry out their biological functions?
a) Folding of different segments of polypeptide chains on each other
b) Formation of a rope like structure
c) Hydrophobic collapse
d) Highly extended structure
View Answer
Explanation: The folding of segments of a polypeptide leads to the formation of a highly compact structure from an extended conformation. This enables globular proteins to extend to include enzymes, transport-motor proteins, etc.
8. Myoglobin is abundantly found in seals and whales.
a) True
b) False
View Answer
Explanation: Muscle myoglobin stores and distributes oxygen in such creatures, which enables them to remain under water for long periods of time. The high content of this protein is the reason for the muscle colour to be almost brown.
9. The term used when a large number of amino acid residues fold into two or more stable, globular structures is _________
a) Fold
b) Motif
c) Super-secondary structure
d) Domain
View Answer
Explanation: Fold, motif and super-secondary structure are synonymous for stable arrangements of secondary structural elements, and a domain, a large protein is result of folding of the many amino acid residues which retains its native structure on subjecting to proteolytic cleavage.
10. The two types of symmetry shown by oligomers are ________
a) Rotational and planar symmetry
b) Planar and helical symmetry
c) Rotational and helical symmetry
d) Planar and circle symmetry
View Answer
Explanation: When the constituent subunits are superimposed and rotated about one or more rotational axes, helical symmetry is observed, while subunits that pack themselves around the axes of rotation to form closed structures show rotational symmetry.
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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