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

What is the lifecycle of amylase according to the lock and key model?

1. Enzyme, substrate, and product exchange

2. Contact, complex formation, and release

3. Enzyme formation, degradation, and recycling

4. Activation, inhibition, and dissolution

The correct answer is: Contact, complex formation, and release

The lifecycle of amylase, as described by the lock and key model, involves the sequence of processes where the enzyme encounters its substrate, forms a complex, and ultimately releases the product. In this model, the enzyme (amylase) has a specific shape that perfectly fits the substrate (starch). When amylase comes into contact with its substrate, the two bind to form a temporary enzyme-substrate complex. This complex undergoes a transformation that helps break down the starch into smaller sugar molecules. Once the reaction is complete, the product is released from the active site of the enzyme, allowing the enzyme to be free to catalyze another reaction cycle. This model emphasizes the specificity of enzyme-substrate interactions and how the enzyme's shape facilitates the reaction, which is central to enzyme functionality.