Question

Quarternary structure of protein _____________________.

• A. Consists of four subunits
• B. May be either $\alpha$ or $\beta$
• C. Is unrelated to two function of the protein
• D. Is dictated by the primary structures of the individual subunits

Answer 1

The correct option is D Is dictated by the primary structures of the individual subunits

Conceptually, protein structure can be understood at four levels. They are primary, secondary, tertiary and quaternary.

• Primary structure includes all the covalent bonds between amino acids and is normally defined by the sequence of peptide-bonded amino acids and locations of disulphide bonds. The relative spatial arrangement of the linked amino acids is unspecified.
• Secondary structure refers to regular recurring arrangements of space of adjacent amino acid residues in a polypeptide chain.
• Tertiary structure refers to the spatial relationship among all amino acids in a polypeptide chain; it is the complete three dimensional structure of a polypeptide.
• Proteins with several polypeptide chains have one more level of structure called the quaternary structure, which refers to the spatial relationship of the polypeptides or subunits within the membrane. The arrangement of proteins and protein subunits in three dimensional complexes or quaternary structure is stabilized and guided by multiple non covalent interactions. The two most common quaternary structures of multisubunit proteins are α-helices in globular proteins and β-sheets in fibrous proteins. The functional properties of multi-subunit proteins depends on the quaternary structure.