Enzymes are protein catalysts that speed up biochemical reactions without being consumed. They are produced by living organisms and work by lowering the activation energy of reactions. Enzymes are used as biocatalysts in industries like food processing and are essential for human digestion and DNA replication. Environmental factors like temperature and pH can impact enzyme activity, as can cofactors and inhibitors. Biocatalysts offer advantages over chemical catalysts like milder reaction conditions and higher product quality. They have many applications including food processing, diagnostics, and molecular biology.