Introduction to NCERT Exemplar Solutions for Class 12 Chemistry Chapter 14: Biomolecules
Biomolecules are naturally occurring compounds that are essential for life. They include carbohydrates, proteins, nucleic acids, and vitamins, which perform structural, functional, and regulatory roles in living organisms. Chapter 14 of Class 12 Chemistry explores the structure, properties, and functions of these molecules, providing students with a strong foundation in both organic and biological chemistry. The NCERT Exemplar Solutions for this chapter guide learners through conceptual, application-based, and reasoning problems, ensuring a thorough understanding of biomolecular Chemistry.
Carbohydrates
Carbohydrates are polyhydroxy aldehydes or ketones, classified as monosaccharides, disaccharides, and polysaccharides. Monosaccharides, like glucose and fructose, are simple sugars that act as energy sources. Disaccharides, such as sucrose and lactose, form from two monosaccharides via glycosidic linkage. Polysaccharides like starch, cellulose, and glycogen are polymers of monosaccharides and serve as storage or structural molecules. Exemplar questions test students’ ability to distinguish between reducing and non-reducing sugars, write structural formulas, and explain properties like mutarotation and optical activity. Students also learn about interconversion reactions and the biological significance of carbohydrates.
Proteins
Proteins are polymers of amino acids linked by peptide bonds. They are classified based on structure into primary, secondary, tertiary, and quaternary levels. Proteins serve as enzymes, structural components, hormones, and transport molecules. Exemplar problems often require students to identify amino acids, determine peptide sequences, or explain denaturation effects caused by heat, pH, or chemicals. These questions strengthen the understanding of protein structure-function relationships and their importance in living systems.
Enzymes
Enzymes are biological catalysts that accelerate chemical reactions without being consumed. Their activity depends on substrate specificity, temperature, pH, and coenzymes or cofactors. The Michaelis-Menten kinetics and the concept of activation energy are briefly discussed to explain enzyme action. Exemplar solutions provide reasoning-based questions about the effects of inhibitors and the significance of enzymes in metabolism.
Nucleic Acids
Nucleic acids, such as DNA and RNA, are polymers of nucleotides. Each nucleotide consists of a nitrogenous base, pentose sugar, and phosphate group. DNA stores genetic information, while RNA is involved in protein synthesis. Exemplar questions focus on nucleotide structure, complementary base pairing, and differences between DNA and RNA. Students are also guided to understand the role of nucleic acids in heredity and cellular functions.
Vitamins and Hormones
Vitamins are organic compounds required in small quantities for proper physiological functioning. They are classified as water-soluble (B-complex and C) and fat-soluble (A, D, E, K). Hormones such as insulin and thyroxine regulate metabolism and homeostasis. Exemplar problems often test students’ ability to classify vitamins, explain their deficiency symptoms, and relate their chemical structure to biological function.
Lipids
Lipids are hydrophobic biomolecules, including fats, oils, phospholipids, and steroids. Fats and oils are esters of glycerol and fatty acids and serve as energy storage molecules. Phospholipids are key components of cell membranes, and steroids like cholesterol act as signaling molecules. Exemplar solutions provide reasoning problems to explain lipid structure, properties, and biological significance.