combining acid and protein can cause chemical change
acid is compound. change_in_protein_activity is chemical_interaction. breaking_down_proteins is chemical_reaction. protein_conformational_change is chemical_interaction. change_in_enzyme_activity is not chemical_interaction. protein_conformational_change is not chemical_interaction. breaking_down_proteins is not chemical_reaction. change_in_enzyme_activity is chemical_interaction. acid is not compound. change_in_protein_activity is not chemical_interaction.