Answer the question on the basis of passage given below:

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids etc. Proteins and carbohydrates are essential constituents of our food. Carbohydrates are primarily produced by plants and form a very large group of naturally occurring organic compounds. SOme common examples are cane sugar, glucose, starch etc.

Match List I with List II

Choose the correct answer from the options given below:

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

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

Let us go through each category and its corresponding linkage in detail:

1. Carbohydrates – Ether Linkage

Carbohydrates, such as sugars and starches, consist of carbon, hydrogen, and oxygen atoms. They are primarily linked by glycosidic linkages, which are a type of ether linkage.  In disaccharides (e.g., sucrose) and polysaccharides (e.g., starch, cellulose), the glycosidic bond connects the anomeric carbon of one sugar to the hydroxyl group of another sugar. This bond is formed through a dehydration reaction (water loss) between the hydroxyl groups of the two sugars.

Example: In sucrose (table sugar), glucose and fructose are linked by an α(1→2) glycosidic bond.

\(\text{Glucose} + \text{Fructose} \rightarrow \text{Sucrose} + \text{H}_2\text{O}\)

2. Proteins – Amide Linkage

Proteins are composed of amino acids linked by peptide bonds, which are a type of amide linkage. A peptide bond forms between the amino group (-NH₂) of one amino acid and the carboxyl group (-COOH) of another. This bond results from a dehydration reaction, where a molecule of water is released. The peptide bond is crucial for forming polypeptide chains, which then fold into functional proteins.

Example: The dipeptide glycine-alanine is formed by a peptide bond between the carboxyl group of glycine and the amino group of alanine.

\(\text{Glycine} + \text{Alanine} \rightarrow \text{Glycyl-Alanine} + \text{H}_2\text{O}\)

3. Nucleic Acids – Phosphodiester Linkage

Nucleic acids (DNA and RNA) are polymers of nucleotides. The nucleotides are linked by phosphodiester bonds. This bond forms between the phosphate group of one nucleotide and the hydroxyl group on the sugar of the adjacent nucleotide. This linkage creates the backbone of nucleic acid strands, consisting of alternating sugar and phosphate groups, with the nitrogenous bases extending from the sugar.

Example: In DNA, the phosphodiester bonds connect the 3'-hydroxyl group of one nucleotide to the 5'-phosphate group of the next nucleotide

\(\text{Nucleotide}_1 + \text{Nucleotide}_2 \rightarrow \text{Nucleotide}_1-\text{Phosphate}-\text{Nucleotide}_2\)

4. Lipids – Ester Linkage

Lipids, such as triglycerides, are made up of glycerol and fatty acids. The fatty acids are connected to the glycerol backbone by ester linkages. An ester bond is formed between the carboxyl group (-COOH) of a fatty acid and the hydroxyl group (-OH) of glycerol. This reaction produces water and forms the ester bond, which is a key feature of triglycerides (fats and oils).

Example: In triglycerides, three fatty acids each form an ester bond with a glycerol molecule.

\(\text{Glycerol} + 3\text{Fatty Acids} \rightarrow \text{Triglyceride} + 3\text{H}_2\text{O}\)

These linkages define the structure and function of each macromolecule and are fundamental to their biological roles.