(a) (i) What is meant by an enzyme’s optimum pH? (ii) What is a denatured enzyme? (b) In the course of your studies you investigated the effect of denaturation by heat application on the activity of an enzyme - Leaving Cert Biology - Question 9 - 2008

A denatured enzyme is one that has lost its native structure and, consequently, its functional activity. This loss can be caused by factors such as extreme temperatures or pH levels, leading to the alteration of the enzyme's three-dimensional shape, which is essential for its biological activity.

The enzyme used was catalase.

The substrate used was hydrogen peroxide (H₂O₂).

To investigate the effect of denaturation by heat, I prepared several test tubes containing a fixed amount of hydrogen peroxide. I then heated separate test tubes to different temperatures (e.g., 30°C, 50°C, and 70°C) while keeping one as a control at room temperature. After heating, I added an equal amount of catalase to each test tube and measured the amount of oxygen produced within a set time period using a gas syringe. This allowed me to quantify the enzyme's activity under the varying conditions.

The results showed that the enzyme catalase was most active at room temperature and began to lose activity significantly at 50°C, with little to no oxygen production observed at 70°C. The control demonstrated the highest volume of oxygen released, illustrating the importance of optimal conditions for enzyme function.