NEET UG BIOLOGY MCQ: BIOMOLECULES

Solution approach

1. Correct Answer + Core Reason: Primary structure of proteins is due to the presence of peptide bonds.
   
   Step-by-Step Solution:
   
   Step 1: Define primary structure. The primary structure of a protein refers to the linear sequence of amino acids that make up the polypeptide chain.
   
   Step 2: Explain the role of peptide bonds. The amino acids in the primary structure are linked together by peptide bonds, which are covalent bonds formed between the carboxyl group of one amino acid and the amino group of the next.
   
   Step 3: Consider the other options:
   - Covalent bond: A general term, but peptide bonds are the specific covalent bonds in primary structure.
   - Disulphide bond: Important for tertiary structure.
   - Ionic bonds: Can contribute to tertiary structure.
   
   Step 4: Conclusion: Peptide bonds are responsible for the primary structure of proteins.
   
   Why other options are wrong:
   - Option B: Covalent bonds is a general term; peptide bonds are the specific covalent bonds.
   - Option C: Disulphide bonds contribute to tertiary structure, not primary.
   - Option D: Ionic bonds contribute to tertiary structure, not primary.
   
   Key Concepts:
   - Protein structure (primary, secondary, tertiary, quaternary)
   - Peptide bond
   
   Memory Aids:
   - Primary = Peptide bonds
   
   Quick Tips:
   - Remember the hierarchy of protein structure: primary, secondary, tertiary, quaternary.