OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Why are enzymes considered specific?

1. They have multiple active sites

2. They can act on any substrate

3. Each enzyme has its own specific substrate they bind to

4. Enzymes work best at any substrate concentration

The correct answer is: Each enzyme has its own specific substrate they bind to

Enzymes are considered specific because each enzyme has a unique three-dimensional structure that determines its function. This structure includes a specific active site that is designed to bind to a particular substrate. The shape and chemical environment of the active site fit only certain substrates, much like a key fits into a specific lock. This specificity means that an enzyme will facilitate a particular reaction involving its corresponding substrate, ensuring that biochemical processes within organisms work efficiently and correctly. The uniqueness of the active site is crucial as it not only binds the substrate but also catalyzes the chemical reaction, promoting the transformation of the substrate into products. This specificity is vital in biological systems because it prevents unwanted reactions and ensures that metabolic pathways occur in an orderly and controlled manner. Thus, the reason for enzyme specificity lies in the precise interaction between the enzyme and its substrate, which is a fundamental concept in understanding enzyme function and regulation in biological systems.