A substance that speeds up a chemical reaction without being consumed in the process is called a catalyst. Catalysts lower the activation energy required for reactions, enabling them to occur more quickly or at lower temperatures. They participate in the reaction but remain unchanged at the end, allowing them to be used repeatedly. Enzymes, which are biological catalysts, play a crucial role in facilitating various metabolic processes in living organisms, highlighting the importance of catalysts in both organic and inorganic chemistry.