Morphological differences between cells and the exis- tence of morphologically distinct particles have been examined since cells were first recognized. Each techno- logical advance in detection and visualization has led to the description of different organelles and cell types. Basic biochemical processes in cells were recognized and are now weIl understood. It is only recently however, that research has expanded to include the specific meta- bolic function of the specialized cell types and organelles. In some cases metabolic roles were recognized when the organelles were first described,...