Question

Match List-I with List-II
{|p{7cm}|p{7cm}|} List-I (Column A) & List-II (Column B)
(A) n-hexadecanaic acid & (I) Watson and Crick
(B) Secondary amino group & (II) Proline
(C) Double helical DNA & (III) Palmitic acid
(D) Enantiomer & (IV) Optical isomer

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (I), (B) - (III), (C) - (II), (D) - (IV)
• (A) - (I), (B) - (II), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (II), (C) - (I), (D) - (IV)

Hint:

Remembering that Proline is the only standard amino acid with a secondary amine (imino) group helps you quickly match (B) with (II).
This immediately narrows down the options in similar biochemical matching questions.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This matching question covers fundamental biochemical terms, molecular structures, historical scientific discoveries, and stereochemistry.
Each matched pair represents a key standard definition or relationship in biochemistry.

Step 3: Detailed Explanation:
Let us analyze each of the matched pairs individually:
(A) n-hexadecanoic acid:
n-hexadecanoic acid (spelled as "n-hexadecanaic acid" in the question paper) is the systematic IUPAC name for Palmitic acid.
It is a common saturated fatty acid with the chemical formula $\text{CH}_3(\text{CH}_2)_{14}\text{COOH}$.
Hence, (A) matches with (III).
(B) Secondary amino group:
Among the twenty standard amino acids, Proline is unique because its side chain cyclic structure bonds back to the nitrogen atom of the amino group.
This forms a rigid five-membered pyrrolidine ring, making it a secondary amino acid (historically called an imino acid).
Hence, (B) matches with (II).
(C) Double helical DNA:
The double-helix molecular structure of Deoxyribonucleic Acid (DNA) was famously solved and proposed by James Watson and Francis Crick in 19
Hence, (C) matches with (I).
(D) Enantiomer:
An enantiomer is one of two stereoisomers that are non-superimposable mirror images of each other.
Because they rotate plane-polarized light in opposite directions, they are classified as optical isomers.
Hence, (D) matches with (IV).

Step 4: Final Answer:
Matching the columns yields:
(A) - (III), (B) - (II), (C) - (I), (D) - (IV).
This corresponds to Option (D).