Match List I with List II

Choose the correct answers from the options given below:

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

The correct answer is option 4. A-IV, B-III, C-I, D-II.

A. Glycosidic linkage → IV. Linkage between two monosaccharide units

Glycosidic linkage is the bond that forms between two monosaccharides (simple sugars) through a dehydration reaction (removal of water). This bond typically involves the hydroxyl group of one monosaccharide reacting with the anomeric carbon of another monosaccharide. It is the key structural linkage in carbohydrates (like disaccharides, oligosaccharides, and polysaccharides). For example, in sucrose (table sugar), the glycosidic bond links glucose and fructose. Thus, A matches with IV (Linkage between two monosaccharide units).

B. Peptide linkage → III. Linkage between two amino acids

Peptide linkage (or peptide bond) is the amide bond that forms between two amino acids during protein synthesis. It is formed by a condensation reaction between the carboxyl group (-COOH) of one amino acid and the amino group (-NH2) of another, releasing water. This bond is fundamental to the formation of peptides and proteins. Example: In the dipeptide formed from glycine and alanine, the peptide bond joins the amino end of glycine to the carboxyl end of alanine. Thus, B matches with III (Linkage between two amino acids).

C. Nucleotide → I. Monomeric units of nucleic acids

A nucleotide is the basic building block (monomer) of nucleic acids, such as DNA and RNA. It consists of three components:

1. A nitrogenous base (adenine, thymine, cytosine, guanine, or uracil in RNA).

2. A five-carbon sugar (ribose in RNA, deoxyribose in DNA).

3. One or more phosphate groups.

Nucleotides link together through phosphodiester bonds to form the backbone of DNA and RNA. Thus, C matches with I (Monomeric units of nucleic acids).

D. Nucleoside → II. Sugar-heterocyclic base combination

A nucleoside consists of only two components:

1. A five-carbon sugar (either ribose or deoxyribose).

2. A nitrogenous base (adenine, guanine, cytosine, thymine in DNA, or uracil in RNA).

Nucleosides are similar to nucleotides but lack the phosphate group. When a phosphate group is added, a nucleoside becomes a nucleotide. Thus, D matches with II (Sugar-heterocyclic base combination).

Thus correct answer is option 4: A-IV, B-III, C-I, D-II.