Match List-I with List-II:

Choose the correct answer from the options given below:

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

The correct answer is Option (4) → (A)-(II), (B)-(IV), (C)-(I), (D)-(III).

Let us explain the matching between the amino acids and their nature in greater detail.

Understanding the Nature of Amino Acids
Amino acids are the building blocks of proteins, and they differ in the side chains attached to their central (α) carbon. These side chains determine the chemical nature of each amino acid: whether it is acidic, basic, neutral, polar, or non-polar, as well as whether it is optically active or inactive.

(A) Valine: (II) Neutral optically active amino acid

Valine is a neutral, nonpolar amino acid. It has a branched aliphatic side chain (isopropyl group), which makes it hydrophobic (water-repelling). Valine is classified as neutral because its side chain does not carry a charge under physiological conditions.

Valine has a chiral center at its α-carbon, meaning it is optically active (can rotate plane-polarized light). All amino acids except glycine have a chiral carbon and are thus optically active.

(B) Glycine: (IV) Neutral optically inactive amino acid

Glycine is the simplest amino acid with just a hydrogen atom as its side chain. This simplicity makes it neutral (nonpolar and uncharged). Since there is no functional group that can ionize in physiological pH, it’s neither acidic nor basic.

Unlike other amino acids, glycine is optically inactive because it has no chiral center. The α-carbon in glycine is attached to two hydrogen atoms, making it achiral (non-chiral).

(C) Lysine: (I) Basic amino acid

Lysine is a basic amino acid. It has an extra amino group (-NH₂) in its side chain, which can accept a proton, giving it a positive charge at physiological pH (around 7.4). This makes lysine basic in nature.

Lysine's positively charged side chain can form interactions with negatively charged molecules like DNA or phosphates, playing an important role in the structure and function of proteins.

(D) Glutamic acid: (III) Acidic amino acid

Glutamic acid is an acidic amino acid. It has an extra carboxyl group (-COOH) in its side chain, which can lose a proton and become negatively charged (forming the glutamate ion) at physiological pH. This additional carboxyl group makes glutamic acid acidic in nature.

Glutamic acid is involved in protein synthesis and serves as a precursor for the synthesis of other amino acids.

Thus, the correct option is: (A)-(II), (B)-(IV), (C)-(I), (D)-(III).