Enzyme Kinetics & Michaelis-Menten

How enzymes speed up reactions

Enzymes are biological catalysts that lower activation energy by forming a specific enzyme-substrate (ES) complex at the active site (lock-and-key or induced fit). The catalytic cycle: E + S ⇌ ES → E + P. The Michaelis-Menten model describes reaction rate (v) as a function of [S]: v = Vmax[S]/(Km + [S]). Km (Michaelis constant) is the [S] at half-Vmax — a measure of enzyme-substrate affinity (lower Km = higher affinity). Competitive inhibitors increase apparent Km (compete with substrate for active site). Non-competitive inhibitors decrease Vmax (bind allosteric site, alter enzyme shape). Uncompetitive inhibitors decrease both Km and Vmax (bind ES complex only). Temperature and pH also affect enzyme activity by denaturing the protein.