The molecule ATP (adenosine triphosphate) can function as a coenzyme. When a phosphate group is removed, turning ATP into ADP (adenosine diphosphate), energy is released. Since several chemical reactions require energy, cells can use ATP to provide energy to a reaction to help alter the substrate into product. The substrate may be temporarily phosphorylated or have a phosphate group added. The phosphate group can then be removed and the product is formed partly through the addition and removal of a phosphate. Fig 2: structure of ATP.2. Coenzymes often have long, complex names and are often shortened to abbreviations. Coenzymes with abbreviated names include: NAD+/NADH, NADP+/NADPH, and FAD/FADH2. They work similarly to ATP, except instead of a molecular group they eliminate or add electrons and hydrogen atoms. therefore, they have two different forms: NAD+ and NADH are the same molecule, except that hydrogen has been added to NADH. 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 typically 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 many different ways