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

How can the reactions in a cell's metabolism be sped up?

1. By decreasing enzyme concentration

2. By lowering temperature

3. By increasing substrate concentration

4. Usually by raising the temperature

The correct answer is: Usually by raising the temperature

The correct answer highlights that raising the temperature generally speeds up the reactions in a cell's metabolism. This is primarily because an increase in temperature provides more kinetic energy to the molecules involved, leading to more frequent and energetic collisions between enzymes and substrates. As a result, the likelihood of reactions occurring increases, which can enhance the rate of metabolic reactions. While enzyme concentration can influence the overall rate of reactions, the question specifically pertains to speeding up the reactions themselves rather than altering the availability of enzymes. Lowering the temperature would reduce the kinetic energy, slowing down the reaction rates. Increasing substrate concentration can also enhance reaction rates, but this is often dependent on enzyme availability and may not universally lead to faster reactions if the enzymes become saturated. In contrast, raising the temperature typically has a direct positive effect on the speed of metabolic reactions.