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

How does increasing temperature affect enzyme activity?

1. It decreases the rate of reactions

2. It increases the rate of reactions

3. It has no effect on enzyme activity

4. It stops the enzyme from working entirely

The correct answer is: It increases the rate of reactions

Increasing temperature typically increases the rate of enzyme activity, up to a certain point. Enzymes are proteins that act as catalysts in biochemical reactions, and as the temperature rises, the kinetic energy of the enzyme and substrate molecules increases. This phenomenon enhances the likelihood of collisions between the two, thus speeding up the reaction rate. However, it's important to note that this effect is only observed within a specific temperature range. Each enzyme has an optimal temperature at which it performs best. Beyond this optimal temperature, higher temperatures can lead to denaturation, where the enzyme's structure becomes altered and its active site can no longer bind to the substrate effectively. This means that while increasing temperature can initially boost enzyme activity, there is a limit to how much temperature can be raised before the enzyme starts to lose functionality.