Q. The correct statement about peptides and proteins is
A) In α-helices, the polypeptide chain is twisted into a left-handed screw (helix) through intramolecular hydrogen bonds
B) Tertiary structure of proteins has two or more polypeptide subunits
C) Only the proteins having a quaternary structure are biologically active
D) In β-pleated sheet structures, peptide chains are held together by intermolecular hydrogen bonds
Explanation
[Solution from source] In the β-pleated sheet, neighbouring chains are linked by hydrogen bonds between chains (intermolecular). The α-helix is right-handed; several subunits make quaternary (not tertiary) structure; and many single-chain proteins are fully active. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.