BharatNotes What is Enzymes?
Enzymes are biological catalysts that speed up the chemical reactions of living cells without themselves being used up. Most enzymes are proteins, though some are catalytic RNA molecules called ribozymes. They work by binding a reactant — called the substrate — at a specific pocket known as the active site, and lowering the activation energy (the energy barrier reactions must cross), so the reaction proceeds far faster than it would unaided.
Two models explain this fit. The older lock-and-key model treats the active site as a rigid shape complementary to the substrate. The widely accepted induced-fit model holds that the enzyme is flexible and adjusts its shape on substrate contact, better stabilising the transition state and lowering activation energy. Both explain enzyme specificity — why one enzyme typically acts on one substrate or reaction.
Classification and Cofactors
The International Union of Biochemistry and Molecular Biology (IUBMB) assigns each enzyme a four-digit Enzyme Commission (EC) number whose first digit gives its class.
| EC class | Enzyme type | What it does |
|---|---|---|
| 1 | Oxidoreductases | Transfer electrons (oxidation-reduction) |
| 2 | Transferases | Transfer functional groups between molecules |
| 3 | Hydrolases | Break bonds using water (e.g. digestive enzymes) |
| 4 | Lyases | Add/remove groups to form double bonds |
| 5 | Isomerases | Rearrange atoms within a molecule |
| 6 | Ligases | Join two molecules using energy (e.g. ATP) |
Many enzymes need non-protein helpers: inorganic cofactors (metal ions like Zn, Mg) or organic coenzymes (often vitamin-derived, such as NAD/NADP). Activity is also controlled by inhibitors — competitive inhibitors compete for the active site, while non-competitive inhibitors bind elsewhere (an allosteric site) and change the enzyme's shape.
Factors and Significance
Each enzyme has an optimum temperature and pH. Beyond these, enzymes denature — losing the three-dimensional shape of the active site — and become inactive. Familiar human digestive enzymes show this: salivary amylase (carbohydrates), pepsin (proteins, acidic stomach pH) and pancreatic trypsin and lipase (proteins and fats in the small intestine).
Industrially, enzymes enable greener, lower-energy processes. Alkaline proteases power bio-detergents; pectinases and cellulases aid food and juice processing; and thermostable enzymes serve textile and paper industries. Because most commercial enzymes are mesophilic — most active roughly 20-45°C at near-neutral pH — research increasingly targets thermostable and extremophile-derived enzymes for harsher industrial conditions (peer-reviewed reviews, as of 2026).
UPSC Angle
Focus on the essentials: enzymes lower activation energy, are reaction-specific, denature with heat and pH extremes, and are not consumed. Link them to biotechnology, the bio-economy and pollution control for GS3. This is a foundation concept — no direct PYQ maps to the exact term, but it underpins recurring questions on biotechnology, digestion and industrial science.
