Formation of the tertiary structure culture on fold of a protein- held together by non-covalent interactions

• A. Primary structure of proteins
• B. Secondary structure of proteins
• C. Tertiary structure of proteins
• D. Quaternary structure of proteins

Answer: (C)

The ending three-dimensional shape of a single polypeptide, folded into a unique arrangement, is held together by non-covalent interactions among side chains and the backbone. This is the tertiary structure. It describes how the whole chain coils into a global 3D form that determines the protein’s function, extending beyond the local patterns of the secondary structure (like helices and sheets) and the linear sequence of amino acids (primary structure). Quaternary structure, by contrast, would involve how multiple polypeptide chains fit together. Non-covalent forces such as hydrogen bonds, ionic interactions, hydrophobic packing, and van der Waals attractions are central to stabilizing this final fold (though covalent disulfide bonds can also contribute in some proteins).