Enzymes are specialized proteins that catalyze biochemical reactions, significantly increasing reaction rates without being consumed. They work by binding to specific substrates at their active sites, forming enzyme-substrate complexes that lower the activation energy needed for the reaction. For example, the enzyme amylase breaks down starch into sugars during digestion. Enzymes are crucial for maintaining homeostasis and regulating processes like metabolism, DNA replication, and energy production. Factors like pH, temperature, and inhibitors affect enzyme activity, making their proper functioning essential for health and survival.