Golgi Apparatus

                      Golgi Apparatus, also Golgi body or Golgi complex,
                      network of stacked sacs found within nucleated cells
                      that store, package, and distribute the proteins and
                      lipids made in the endoplasmic reticulum.

                      The Golgi apparatus was first described by Italian
                      anatomist Camillo Golgi in the late 19th century.
                      Located near the nucleus, each apparatus consists of
                      a stack of six or seven flattened, membrane-bound
                      sacs, or cisternae, each separated by a narrow space.
                      The Golgi apparatus is cup-shaped with the convex
                      end, or cis cisterna, facing the cell nucleus and the
                      concave end, or trans cisterna, facing the cell surface.
                      The number of Golgi apparatus in each cell varies but
                      averages between 10 and 20 in animal cells and up to
                      several hundred in plant cells.

                      Proteins and lipids manufactured in the endoplasmic
                      reticulum bud off in tiny, hollow structures, or vesicles,
                      and fuse with the cis cisterna of the Golgi apparatus.
                      The proteins and lipids move progressively through the
                      stack of cisternae until they reach the trans cisterna.
                      There they may be modified by the attachment of
                      lipids or carbohydrates. The proteins and lipids are
                      enclosed in a membrane to form a vesicle so that they
                      do not affect the rest of the cell. The vesicles are
                      then sorted and their destination is determined.

                      Proteins that are meant to return to the endoplasmic
                      reticulum carry a distinctive tag. The Golgi apparatus
                      recognizes the tag and transports the proteins back to
                      the endoplasmic reticulum. Some proteins and lipids are
                      sent to the surface of the cell to be released into the
                      external environment. Others are transferred to the
                      small structures that hold digestive enzymes, called
                      lysosomes.

                      The Golgi apparatus also manufactures long-chained
                      sugars called polysaccharides that cells secrete into
                      their external environments. Examples include cellulose
                      and pectin used to construct plant cell walls, and the
                      polysaccharides in the mucus of animal cells.


                      Contributed By: John B. Ferguson, Sc.B., M.Phil., Ph.D.
                      Professor of Biology, Division of Natural Sciences and
                      Mathematics, Bard College. Director, Distinguished
                      Scientist Lecture Series, Bard Center.
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