Kaplan Nursing Entrance Practice Exam

What is the primary role of enzymes in biological reactions?

1. To slow down reactions

2. To act as substrates

3. To act as catalysts

4. To be used up in reactions

The correct answer is: To act as catalysts

The primary role of enzymes in biological reactions is to act as catalysts. Catalysts are substances that increase the rate of a chemical reaction without themselves undergoing any permanent change. Enzymes are a specific type of catalyst composed of proteins, and they work by lowering the activation energy required for a reaction to occur. This allows biological processes to proceed at a much faster rate than they would without the presence of enzymes, making them essential for sustaining life. Enzymes achieve this by binding to reactant molecules, known as substrates, and facilitating their conversion into products. They do this through various mechanisms, such as providing an ideal environment for the reaction to occur or stabilizing transition states. Importantly, after the reaction, enzymes remain unchanged and can be reused for subsequent reactions, highlighting their role as catalysts rather than being consumed in the process. This enzymatic activity is crucial in numerous biological functions, including digestion, metabolism, and DNA replication, emphasizing the indispensable role of enzymes in maintaining life processes.