Question

Consider the following statements: Statement-I: Primary structure of protein represents its constitution. Statement-II: \( \alpha \)-Helix and \( \beta \)-pleated sheet structure of protein represent tertiary structure of it. The correct answer is:

• A. Both statement-I and statement-II are correct
• B. Both statement-I and statement-II are not correct
• C. Statement-I is correct, but statement-II is not correct
• D. Statement-I is not correct, but statement-II is correct

Hint:

Protein folding occurs in four stages: primary (sequence), secondary (local folding), tertiary (3D shape), and quaternary (multiple chains).

Answer 1

The Correct Option is C

Step 1: Understanding Protein Structures Proteins have four levels of structure: 1. Primary structure: The sequence of amino acids in a polypeptide chain, determining the protein’s fundamental constitution. 2. Secondary structure: Includes \( \alpha \)-helix and \( \beta \)-pleated sheet, formed by hydrogen bonding between backbone atoms. 3. Tertiary structure: The three-dimensional folding due to interactions between side chains (hydrophobic interactions, ionic bonds, disulfide bridges). 4. Quaternary structure: Association of multiple polypeptide chains to form a functional protein. Step 2: Evaluating Statements - Statement-I is correct: Primary structure indeed represents a protein’s constitution. - Statement-II is incorrect: \( \alpha \)-helix and \( \beta \)-pleated sheet belong to secondary structure, not tertiary. Conclusion Thus, the correct answer is: \[ \text{Statement-I is correct, but Statement-II is not correct.} \]