The primary function of enzymes in the human body is to act as biological catalysts that speed up chemical reactions. Enzymes are crucial for various metabolic processes, including digestion, energy production, and DNA replication. Without enzymes, many of these reactions would occur too slowly to sustain life. They work by lowering the activation energy required for a reaction to take place, allowing the body to efficiently utilize nutrients and maintain homeostasis. Each enzyme is specific to a particular reaction or type of substrate, ensuring precision in the body's biochemical pathways and facilitating the myriad of processes necessary for health.