But now we know that some enzymes are actually RNA molecules. So RNA molecules, certain RNA molecules also have the ability to catalyze reactions as we'll see eventually. And the last thing we're going to mention about enzymes is enzymes are not actually used up or not depleted in chemical reactions. And if enzymes are changed or altered in some way in the reaction at the end of that reaction the enzyme will assume its original shape and original structure. So enzymes are not used up and remain unchanged at the end of the reaction. Now, this is not to say that enzymes during the reaction are unchanged in some way.