Which statement is true of enzymes? they are proteins
they are nucleic acids
they are lipids
they are carbohydrates

Enzymes- are proteins which function as biological catalysts

so, the answer is that they are proteins.

1.the evidene of the reaction

2.yes

3.yes

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.