Question

Quaternary structure is found in
(A) Simple monomeric protein
(B) Conjugated monomeric protein
(C) Oligoprotein
(D) Both B and C

Answer 1

Quaternary structure is made up of more than two polypeptides. These polypeptides are joined by means of interaction between the proteins. These interactions are disulfide bonds, Hydrogen bonds and salt bridges etc. These interactions provide the proper conformation to the quaternary structure.

Complete step-by-step answer:
Protein is defined as the polymer structure of amino acids. The amino acids are joined by peptide bonds. In this bond, the carboxyl group of one amino acid reacts with the amino group of another amino acid. Water molecule is released in this process. This bond formation is a kind of condensation reaction.
Simple monomeric protein refers to the protein structure which consists of only one kind of polypeptide. This monomeric protein consists of many amino acids. That’s why “Option A” is incorrect.
Conjugated monomeric protein has single polypeptide and non proteinaceous part also. This non proteinaceous part enhances the stability and activity of conjugated monomeric protein. That’s why “Option B” is incorrect.
Oligo Protein is made up of more than two polypeptides. Which are subunit chains that show spatial arrangement and nature of interaction. A quaternary protein structure is dimer that possesses two identical subunits of polypeptides. Together with others linked by different bonds to stabilize the structure and form multimers.

Hence the correct option is Option C.

Additional information:
Quaternary structures are stabilized by means of interactions between the polypeptides. There are found intra as well as inter interaction in the polypeptide and between the polypeptides respectively. Disulfide bond, hydrogen bond and salt bridges are found which stabilize the quaternary structure.

Note:
Quaternary structure consists of four polypeptides. For example: Haemoglobin. Quaternary structure is an example of oligomeric protein because there are more than two polypeptides in haemoglobin. Interactions such as salt bridges, hydrogen bond and disulfide bond stabilize the structure and provide the functional form to quaternary structure.