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

What is the role of enzymes in respiration?

1. To create energy

2. To speed up the reaction

3. To store energy

4. To transport oxygen

The correct answer is: To speed up the reaction

Enzymes play a crucial role in respiration by acting as biological catalysts. Their primary function is to speed up the chemical reactions involved in the process of respiration. In cellular respiration, enzymes lower the activation energy required for the reactions to occur, which significantly increases the rate at which glucose and oxygen are converted into energy, carbon dioxide, and water. Without enzymes, these reactions would take place at a much slower rate, making it difficult for cells to meet their energy demands efficiently. The enzymes involved in respiration facilitate various biochemical pathways, such as glycolysis and the citric acid cycle, allowing cells to efficiently extract energy from nutrients. By increasing the speed of these reactions, enzymes ensure that energy is made available to the cell as quickly as needed to support essential functions. In this context, while energy creation, storage, and oxygen transportation are important components of respiration and cellular metabolism, they are not the direct roles of enzymes. Instead, it is the acceleration of reactions that is the defining role enzymes play in respiration.