Budding Vesicles in Living Cells; March 1996; Scientific American Magazine; by Rothman, Orci; 6 Page(s)
All nucleated cells--whether in colonies of yeast or in plants and people--have a complex internal organization resembling that of a well-run city. Perhaps most notably, cell and city both rely on the coordinated activities of specialized departments. In cells these departments are walled off by membranes and called organelles.
A brief tour of some of the more important departments in a cellular "city" might start at the outer membrane, itself an organelle. This structure is akin to the gated walls that once enclosed ancient cities, in that it controls the entry of food and other materials and the export of products manufactured within. Another critical department lies deep inside cells and serves as a manufacturing center. It is here, in the endoplasmic reticulum, that many proteins--the main working parts of cells--are produced. These newly made proteins are then transported to yet another department, the Golgi apparatus, where they are modified (often by the addition of sugars) and ultimately shipped to other destinations within or outside the cell. The Golgi, then, is a major distribution hub for our microscopic cities.