An enzyme is a special type of protein that helps speed up chemical reactions in living organisms. They act as catalysts, meaning they lower the energy needed for a reaction to occur, making processes like digestion and metabolism more efficient. Each enzyme is specific to a particular reaction or type of molecule, often working on substances called substrates. For example, the enzyme amylase helps break down starches into sugars in our mouths and digestive systems. Without enzymes, many essential reactions would happen too slowly for life to exist. They are crucial for everything from breaking down food to building DNA, making them vital for all living things.