Biomolecules: The Chemical Basis of Life

Biomolecules are organic molecules produced by living organisms that are essential for biological processes. The four major classes are carbohydrates, proteins, lipids, and nucleic acids. In the NEET syllabus, OC-09 focuses on carbohydrates, proteins, vitamins, and nucleic acids.

Hierarchy of Carbohydrate Classification:

Carbohydrates
├── Monosaccharides (cannot be hydrolysed further)
│   ├── Trioses (C3): Glyceraldehyde
│   ├── Pentoses (C5): Ribose, Deoxyribose
│   └── Hexoses (C6): Glucose, Fructose, Galactose
├── Disaccharides (hydrolyse → 2 monosaccharides)
│   ├── Sucrose (Glu + Fru) — non-reducing
│   ├── Lactose (Glu + Gal) — reducing
│   └── Maltose (Glu + Glu) — reducing
└── Polysaccharides (hydrolyse → many monosaccharides)
    ├── Starch (amylose + amylopectin) — plant storage
    ├── Glycogen — animal storage
    └── Cellulose — plant structural

All carbohydrates follow the general empirical formula $\text{C}_n(\text{H}_2\text{O})_n$ (hence "hydrates of carbon"), though this is only an approximation — the actual molecular structures are more complex.