Enzymes are chemically

Concept: Enzymes are biological catalysts (biocatalysts) that speed up biochemical reactions without themselves being consumed. Almost all enzymes are built from long chains of amino acids folded into a specific three-dimensional shape; a pocket in that shape, the active site, binds a substrate and lowers the reaction's activation energy.

Application: The question asks for the chemical class enzymes belong to. Since an enzyme's catalytic power comes from its folded amino-acid chain and active site, enzymes are chemically classified as proteins.

Cross-check — ruling out the other options by what each one actually is:

• Carbohydrate: chains of sugar units used for energy storage/structure (e.g., starch, glycogen, cellulose) — no amino-acid chain, so no active site.

• Acid: a chemical property (proton donor, lowers pH), not a class of biomolecule at all.

• Lipid: built from fatty acids and glycerol, used for energy storage and membranes — again no amino-acid backbone.

None of these three has the folded amino-acid structure a catalyst of this kind needs, which confirms the chemical classification of enzymes as proteins.