Chapter 10 — Biomolecules

Biomolecules are complex organic molecules — including carbohydrates, proteins, nucleic acids, lipids, vitamins, and hormones — that form the structural and functional basis of all living systems.

Class 12 Chemistry Chapter 10 covers the major biomolecules essential to life. Carbohydrates (monosaccharides, oligosaccharides, polysaccharides) serve as energy sources and structural materials; glucose (C6H12O6) is the most abundant organic compound on earth. Proteins are polymers of alpha-amino acids linked by peptide bonds, existing as fibrous or globular types with four levels of structure. Nucleic acids — DNA and RNA — are polynucleotides that store and transmit genetic information and direct protein synthesis. Vitamins are classified as fat-soluble (A, D, E, K) or water-soluble (B group, C), and hormones act as intercellular messengers regulating body functions.

1. 01Carbohydrates are polyhydroxy aldehydes or ketones classified as monosaccharides, disaccharides, or polysaccharides based on hydrolysis behaviour; sucrose on hydrolysis yields glucose and fructose
2. 02Glucose (C6H12O6) is an aldohexose that exists in open-chain and cyclic (pyranose) forms; the two cyclic anomers are called alpha- and beta-glucose
3. 03Proteins are polymers of about 20 alpha-amino acids joined by peptide bonds; essential amino acids (10 in number) cannot be synthesised by the body and must come from diet
4. 04DNA contains deoxyribose sugar and the base thymine, whereas RNA contains ribose sugar and uracil; adenine pairs with thymine and cytosine pairs with guanine in DNA's double helix
5. 05Vitamins A, D, E, and K are fat-soluble (stored in liver and adipose tissue); B-group vitamins and vitamin C are water-soluble and must be regularly supplied in diet
6. 06Hormones are chemical messengers secreted by endocrine glands; insulin lowers blood glucose, glucagon raises it, and thyroxine deficiency causes hypothyroidism