Biomolecules Notes for NEET

Enzyme Properties and Classification for NEET Preparation

Enzymes as biological catalysts exhibit properties that NEET tests through conceptual and application-based questions. Key properties include substrate specificity (each enzyme acts on a specific substrate), temperature and pH optima (activity peaks at optimal conditions and declines beyond), and the ability to lower activation energy without being consumed in the reaction. The lock-and-key model proposes rigid enzyme-substrate complementarity, while the induced fit model suggests the enzyme active site adjusts its shape upon substrate binding. Competitive inhibitors resemble the substrate and bind to the active site, increasing the apparent Km without affecting Vmax, while non-competitive inhibitors bind to an allosteric site, reducing Vmax without changing Km. Enzyme classification into six categories (oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases) with examples from NCERT is tested directly. Cofactors are non-protein components required for enzyme activity: prosthetic groups are tightly bound, coenzymes (NAD+, FADH) are loosely bound organic molecules, and metal ions (Zn, Fe, Cu) are inorganic cofactors.