A Level Biology Practice Exam

What is typically true about the specificity of enzymes?

1. Enzymes can act on a wide variety of substrates

2. Each enzyme catalyzes a specific reaction

3. Enzymes require cofactors to function

4. Enzymes tend to work independently of pH

The correct answer is: Each enzyme catalyzes a specific reaction

Enzymes are biological catalysts that facilitate specific chemical reactions, and each enzyme is tailored to interact with a particular substrate or group of closely related substrates. This specificity arises from the unique shape and chemical environment of the enzyme's active site, which allows it to bind only to specific substrate molecules. The lock-and-key model and the induced fit model illustrate how the enzyme and substrate fit together, further emphasizing the concept that enzymes are selective in the reactions they catalyze. This characteristic specificity is crucial for maintaining the efficiency of metabolic processes in living organisms, ensuring that the right reactions occur at the right time, and preventing unwanted side reactions. In this way, enzymes play a critical role in regulating biological pathways and processes.