1. Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process. They do this by lowering the activation energy required for the reaction to occur.

2. Enzymes are highly specific in their action, meaning they typically catalyze only one or a small number of reactions. This specificity is due to the unique three-dimensional shape of the enzyme's active site, which interacts with specific molecules called substrates.

3. Enzymes are proteins, although some RNA molecules (ribozymes) can also act as catalysts. The protein nature of enzymes gives them the ability to fold into complex shapes that allow for precise binding and catalysis.