1. Biological enzymes are proteins, meaning they have specific shapes depending on bond interactions.

2. The active site of the protein is specific to a certain substrate (the thing being broken down).

3. At temperatures higher than body temperature, the proteins start to lose their structure, as the molecules get too excited.

4. This changes the shape of the active site.

5. The substrate can no longer fit into the active site and therefore the enzyme does not work.