Question

In large proteins, peptide chains are much looped, twisted and folded back on themselves. The folded structure is due to the formation of \rule{2cm{0.15mm} bonds}

• A. phosphodiester
• B. peptide
• C. disulphide
• D. glycosidic

Hint:

Memory trick: Protein folding stability $\rightarrow$ Disulphide bridges (S–S bonds)

Answer 1

The Correct Option is C

Concept: Proteins have different levels of structure:
• Primary structure: Sequence of amino acids (peptide bonds)
• Secondary structure: $\alpha$-helix and $\beta$-pleated sheet (hydrogen bonds)
• Tertiary structure: Folding of the polypeptide chain into a 3D shape

Step 1: Understand protein folding.
The complex folding of protein chains results in loops and twists forming a stable three-dimensional structure.

Step 2: Identify the bond responsible.
Disulphide bonds are formed between sulphur atoms of cysteine residues and stabilize the folded structure.

Step 3: Analyze options.
• (A) Phosphodiester: Found in nucleic acids
• (B) Peptide: Links amino acids (primary structure)
• (C) Disulphide: Stabilizes folded structure (correct)
• (D) Glycosidic: Found in carbohydrates

Step 4: Conclusion.
Thus, disulphide bonds are responsible for stabilizing folded protein structures. Final Answer: Option (C)