1. Active Site: This is a specific three-dimensional region on the enzyme where the substrate binds and the chemical reaction takes place. The active site is shaped to fit the substrate precisely, like a lock and key.

2. Specificity: Enzymes are highly specific, meaning they typically catalyze only one or a very small number of reactions. This specificity arises from the precise fit between the enzyme's active site and its substrate.

3. Temperature and pH: Enzymes have optimal temperature and pH ranges. Outside these ranges, enzyme activity can decrease or even cease altogether. Extreme temperatures can denature the protein, disrupting the active site, while pH changes can affect the charges of amino acids, altering the active site's shape.

Let me know if you'd like more detail on any of these factors!