A non-protein organic molecule that an enzyme needs in order to function, such as NAD, is called a

Explanation

Coenzymes are organic helper molecules, often derived from vitamins, that bind loosely and carry chemical groups or electrons between reactions, and NAD is the classic hydrogen carrier of respiration. Inorganic helpers such as zinc or magnesium ions are cofactors. A prosthetic group is a helper bound tightly and permanently, such as the haem in catalase.