PLEASE HELP MEEE. and are what we call the molecules
before and after a chemical reaction.

In a chemical reaction, the atoms and molecules that interact with each other are called reactants. In a chemical reaction, the atoms and molecules produced by the reaction are called products. In a chemical reaction, only the atoms present in the reactants can end up in the products.

where in your body is there an enzyme that does function at a high or low ph? what is the name of that enzyme and its function?