A Level Biology Practice Exam

Which property of enzymes contributes to their function as biological catalysts?

1. They change shape permanently during reactions

2. They lower activation energy for reactions

3. They are consumed in chemical reactions

4. They are only active at high temperatures

The correct answer is: They lower activation energy for reactions

Enzymes function as biological catalysts primarily by lowering the activation energy required for chemical reactions. This property is crucial because it allows reactions to occur more rapidly and under milder conditions than would otherwise be possible. By reducing the activation energy, enzymes enable substrates to transform into products more easily, facilitating essential metabolic processes within living organisms. This efficient catalysis is essential for sustaining life as it allows for the regulation of biochemical reactions at a pace suitable for cellular function. The other options present characteristics that do not align with the fundamental role of enzymes. Enzymes typically do not change shape permanently during reactions; rather, they may undergo a temporary conformational change as they bind to substrates, but they return to their original shape afterward. Additionally, enzymes are not consumed in chemical reactions; they can be reused multiple times, which is a hallmark of their catalytic nature. Finally, enzymes generally function within specific temperature ranges, with many being inactive at excessively high temperatures, as high heat can denature them and permanently alter their structure.