Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are primarily composed of proteins. Some enzymes also require non-protein molecules called cofactors or coenzymes to function. However, the core structure of the enzyme itself is made up of proteins, which are composed of amino acids.
- Carbohydrates, lipids, and nucleic acids serve other important roles in the cell but do not typically function as enzymes.
Thus, the correct answer is option (A) Proteins.