Golgi apparatus was discovered by Golgi in 1898. This apparatus, which was found virtually in all eukaryotic cells, consists of stacks of flattened, membrane bound sacs, called cisternae. These cisternae together with associated vesicles are called Golgi complex. It is a complex system of interconnected tubules around the central stacks.
Cisternae stacks are continuously formed by fusion f vesicles, which are probably derived by the budding of ser. Their outer convex surface is the forming face, while the inner concave surface is the maturing face. The cisternae break up into vesicles from the latter. The whole stack consists of a number of cisternae thought to be moving from the outer to the inner face.
Fig. 4.9Golgi Complex
Fig. 4.10: This figure shows relationship of endoplasmic reticulum with Golgi apparatus, Lysosome and plasma membrane. Golgi apparatus has two ends, forming face and maturation face. Blebs from tips of ser fuse with Golgi apparatus cisternae at forming face, whereas secretory granules (transport vesicles) are pinched off at the maturation face of golgi apparatus. The arrows show the direction of flow of protein product systhesized on Ribosomes. These proteins are converted into glycoproteins in the golgi apparatus.
Golgi complex is concerned with cell secretions. Secretions are products formed within the cell on ribosomes and then passed to the outside through endoplasmic reticulum and Golgi Apparatus. The secretions are converted into finished product and are packed inside membrane, before export. For example in mammals, the pancreas secretes granules containing enzymes that help in digestion. The Golgi complex has a role in formation of these granules. The proteins or enzymes which have to be transported out of the cell pass through the Golgi Apparatus. The most important function of this apparatus is to modify the proteins and lipids by adding carbohydrates and converting them into glycoproteins or glycolipids.