The primary source of energy for all cellular processes is a molecule known as ATP (adenosine triphosphate). Healthy, active cells constantly replenish their supply of ATP to produce vital cellular energy. However, under conditions of stress, injury, or aging, critical body tissues such as heart and skeletal muscles cannot produce ATP quickly enough to perform optimally. D-ribose, a carbohydrate molecule found in every living organism, facilitates the production of ATP.