The Human Body

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.