(golgi body, dicty-osome) An *
organelle formed from flattened membrane-bound cisternae and a variable number of associated spherical vesicles. In most cells, between three and twelve saucer-like cisternae are stacked together with their concave surfaces directed towards the cell surface. The expanded 'rims' of the cisternae give rise to the surrounding spherical vesicles, which contain the products of biochemical activity within the golgi apparatus. If these vesicles move to the cell surface to release their contents, their membranes become incorporated into the *
plasma membrane. The golgi apparatus is thus important in cell membrane synthesis.
Within the golgi cisternae, synthesis of glycoproteins, which commences on the polyribosomes of the rough *
endoplasmic reticulum, is completed. These are moved within vesicles to the cell surface where they may be discharged from the cell or become incorporated into the cell membrane. Complex polysaccharides are also formed in the cisternae and are similarly distributed in vesicles to the cell surface. Cellulose synthesizing enzymes have been identified in the membranes of these vesicles, but they only become functional when incorporated in the plasma membrane. It is probable that hydrolytic enzymes in the golgi cisternae are organized into membrane-bound *
lysosomes. In some unicellular algae (Haptophyta) scales that have been observed with the electron microscope on the cell surface originate in the golgi apparatus.
