In this activity, students will use construction paper models to view how enzymes catalyze reactions. Students first model and draw a reaction in normal conditions. They try several substrates to determine which fits the active site of the enzyme. This really helps drive how the importance of active site shape to enzyme function. It helps them to understand why only one enzyme will catalyze each reaction. The students then switch to a different version of the enzyme. In this scenario, the enzyme has been denatured and its active site has changed shape. This helps them to understand why changes in temperature and pH alter enzyme function. This activity is great stand-alone or in conjunction with a temperature/pH lab (such as the classic liver and hydrogen peroxide lab).