Caffeine's biochemical effects

There are four ways in which caffeine stimulates the nervous system. of these, one is of primary importance. 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 (of caffeine) that the adenosine blocking remains the dominant factor but a novel occurrence of biochemical effect of phospodiesterase inhibition action will be the conversion of UV rays striking the human skin, which radiation are then converted in the presence of caffeine to more pronounced phospodiesterase inhibition (cellulite fat busting).

The other two laboratory effects of caffeine have been judged insignificant in actual biochemical situations. (not of cosmetic importance)