Final answer:
Enzymes are proteins that act as catalysts in biological reactions, lowering the required activation energy and increasing reaction rates. They are specific to their substrates and are necessary for both anabolic and catabolic processes.
Step-by-step explanation:
Enzymes are proteins that function as biological catalysts in various metabolic processes within living organisms. They are not broken down in reactions; instead, they lower the activation energy required for reactions to occur, which can lead to an increase in the rate of those reactions by millions of times compared to reactions that are not catalyzed by enzymes.
Enzymes are highly specific, meaning that each enzyme works on a particular substrate or type of reaction. Contrary to the options provided, enzymes are also necessary for catabolic reactions, which involve the breakdown of larger molecules into smaller ones, releasing energy in the process. Therefore, the correct statement about enzymes is that they are proteins that function as catalysts.