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

How do enzymes behave at low temperatures during photosynthesis?

1. They work at a faster pace

2. They function normally

3. They become inactive

4. They work at a slower pace

The correct answer is: They work at a slower pace

Enzymes are biological catalysts that speed up chemical reactions, including those involved in photosynthesis. At low temperatures, the kinetic energy of molecules decreases, leading to fewer collisional interactions between enzymes and substrates. This results in a reduction in the rate at which the enzymes can catalyze reactions, causing them to work at a slower pace. While enzymes are not completely inactive at low temperatures, their efficiency and activity levels are diminished. This slowing of enzyme activity can significantly affect the overall rate of photosynthesis, as the processes that depend on these enzymes will also become less efficient. In contrast, at higher temperatures, enzymes generally increase in activity until they reach an optimal point, after which they may denature and lose function. Thus, lower temperatures lead to decreased enzyme efficiency and a slower rate of photosynthesis.