Question

The polypeptide chain in a protein has amino acids linked with each other in a specific sequence. This specific sequence of amino acids is called:

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

Hint:

Primary structure = {Sequence}. If sequence changes → protein function may change.

Answer 1

The Correct Option is A

Concept: Proteins have four levels of structural organization:

• 
  Primary structure – Linear sequence of amino acids.
• 
  Secondary structure – Local folding (α-helix, β-pleated sheet).
• 
  Tertiary structure – Overall 3D folding of a single polypeptide.
• 
  Quaternary structure – Association of multiple polypeptide chains.

Step 1: Understand the question. The question refers to the
specific order in which amino acids are linked.
Step 2: Identify correct structural level. The linear arrangement of amino acids connected by peptide bonds defines the
primary structure. \[ \text{Amino acid}_1 - \text{Amino acid}_2 - \text{Amino acid}_3 - \dots \]
Step 3: Eliminate other options.

• Secondary → hydrogen bonding patterns.
• Tertiary → 3D folding.
• Quaternary → multiple subunits.

\[ \therefore \text{Correct answer = (A)} \]