Enzymes are biological molecules that act as catalysts, speeding up chemical reactions in living organisms. They are primarily proteins, and their specific structure allows them to interact with substrates, the molecules they act upon, to facilitate various biochemical processes. Without enzymes, many essential reactions would occur too slowly to sustain life. Each enzyme is highly specific, meaning it only catalyzes a particular reaction or type of reaction. This specificity is crucial for maintaining the delicate balance of metabolic pathways in cells. Enzymes are involved in processes such as digestion, energy production, and DNA replication, making them vital for life.