The ATP (adenosine triphosphate) molecule can function as a coenzyme. When a phosphate group is removed, turning ATP into ADP (adenosine diphosphate), energy is released. Since many chemical reactions require energy, cells can use ATP to give energy to a reaction to help change the substrate into the product. The substrate may be temporarily phosphorylated or have an added phosphate group. The phosphate group can then be removed and the product is formed in part by the addition and removal of a phosphate. Fig 2: structure of ATP.2. Coenzymes often have long, complex names and are often abbreviated. Coenzymes with abbreviated names include: NAD+/NADH, NADP+/NADPH, and FAD/FADH2. These work similarly to ATP, except that instead of a molecular group, they remove or add electrons and hydrogen atoms. therefore, they have two different forms: NAD+ and NADH are the same molecule, except that NADH has added hydrogen. Additionally, removing or adding electrons can change their shape, allowing them to bind or dissociate (be removed) from an enzyme they are helping.3. Their function is generally to accept atoms or groups from a substrate and transfer them to other molecules. 4. They are less specific than enzymes and the same coenzyme can act as such in a number of different areas.