The correct answer is option 2: Proteins.

Enzymes are specialized proteins that act as catalysts in biochemical reactions. They play a crucial role in speeding up the rate of these reactions by lowering the activation energy required for the reaction to proceed. Enzymes are highly specific molecules that can recognize specific substrates and convert them into specific products.

Proteins are large, complex molecules composed of amino acids. They are formed by the linkage of amino acids through peptide bonds. Enzymes, being proteins, are composed of a chain of amino acids arranged in a specific sequence. This sequence determines the unique structure and function of each enzyme.

Although carbohydrates, fatty acids, and sterols are important biomolecules, they are not enzymes themselves. Carbohydrates are primarily involved in providing energy to the body, while fatty acids and sterols play roles in cell membrane structure and hormone synthesis.

In conclusion, while all enzymes are proteins, not all proteins are enzymes. Enzymes are a specific class of proteins with unique properties that enable them to catalyze biochemical reactions.