As can be seen above, caffeine consists of two carbon/nitrogen rings with oxygen and methyl groups as substituents. The fused rings are similar to those in adenine only the substituents differ. Caffeine is found in coffee, tea, and many soft drinks. There is also some amount of caffeine in chocolate, as well as a closely related stimulant, theobromine. The caffeine in sodas is generally produced from the cola berries, and is either a by-product of the cola flavoring or is added for flavor and stimulant effect. There are four ways in which caffeine stimulates the nervous system. Of these, one is of primary improtance. Another has some level of importance, and the other two only occur at unrealistically high levels of caffeine in the body. The first of these methods, and the most important, is blocking adenosine receptors. As caffeine has a similar structure to the adenosine group, but also has more heavily electrophilic and nucleophilic functional groups than adenosine as, for instance, seen in cyclic AMP. This means that caffeine will fit adenosine receptors as well as adenosine itself will. Thus, cyclic AMP remains active, rather than being broken down. Second among the effects of caffeine is phosphodiesterase inhibition. The phosphodiesterase class of enzymes includes a number of enzymes responsible for breaking down cyclic AMP, thus depriving the body of an energy supply. Caffeine fools phosphodiesterase into attacking it instead, which inhibits the breakdown of cyclic AMP. However, the concentration of caffeine required for this effect to become significant is sufficiently high that the adenosine blocking remains the dominant factor. The other two laboratory effects of caffeine have been judged insignificant in actual biochemical situations. Caffeine can increase the speed of rapid information processing by 10% 1, and a cup of regular (caffeine-containing) coffee after lunch helps to counteract the normal post-lunch dip in ability to sustain concentration, aiding alertness 2. Research has also shown that a couple of cups of coffee help to improve alertness and concentration during night shift hours 3. These findings have been further endorsed by Smith et al 4 who conducted a study in 1993 to examine the effects of coffee on daytime and night-time performance and alertness. The results clearly demonstrated that caffeinated coffee had a beneficial effect on alertness and improved performance in a variety of tasks in both day and night sessions. These effects are especially beneficial to night shift workers as it is known that many industrial accidents occur late into the shift when workers become less attentive.