Here's why:

* Proteins are large, complex molecules made up of amino acids. They have a wide variety of functions, including acting as enzymes, structural components, and signaling molecules.

* Carbohydrates are sugars and starches that provide energy.

* Lipids are fats and oils that provide energy storage and insulation.

* Nucleic acids (DNA and RNA) carry genetic information.

Enzymes are biological catalysts that speed up chemical reactions. Almost all enzymes are proteins, although a few are made of RNA (called ribozymes).