Dictyosome consists of flattened membranous sacs. They look like a stack of pita bread. A cell may have several interconnected stacks. Each cisterna in a stack consists of a membrane. This membrane separates its internal space from the cytosol. Vesicles concentrated near the Golgi apparatus. They are used in the transfer of material between the Golgi and other structures. The number of dictoysomes may be few hundreds in plant cells. But lower organisms have only 4 or less dictoysomes.
After leaving the ER, mans transport vesicles travel to the Golgi apparatus. Golgi apparatus is a center of manufacturing, storing, and transportation. Here. products are modified and then sent to other parts. The Golgi apparatus are extensive in cells specialized for secretion.
Dictyosome generally has two poles. The membranes of cisternae differ in thickness and molecular composition at opposite ends of a stack. The two poles of a Golgi stack are:
(a) The cis-face (or forming face): The cis face is located near ER.
(b) The trans face (or maturing face): This end acts as the receiving and shipping departments of the Golgi apparatus.
Formation of secretions in Dictoysomes
Following steps take place during formation of secretions:
I. Transport vesicles move .material from the ER to the Golgi. A vesicle buds from the ER. They forms transport vesicles. This transport vesicle fuses w ith cis face of Golgi apparatus and transfer its contents to Golgi membrane.
- The trans face gives rise to secretary vesicles. These secretary vesicles pinch off and travel to other sites.
- Products of the ER are modified during transport from the cis pole to the trans pole of the Golgi Proteins. Various Golgi enzymes modify oligosaccharide portions of glycoproteins. The oligosaccharides of glycoproteins are identical in the ER. The Golgi removes some sugar monomers and substitutes others. So they produce different types of oligo saccharides. The trans face of the ribosomes budded of as secretary vesicle.
- The secretary vesicles fuse with the plasma membrane. This product is finally exported outside.
Functions of Golgi apparatus
Golgi complex performs following functions:
I. Cell secretions: Golgi complex are concerned with cell secretions. For example in mammals, the pancreas secretes granules. These granules contain enzymes that help in digestion.
- Transportation: Golgi apparatus transport the proteins or enzymes outside the cell.
- Formation of Glyeoproteins and glycolipids: It is the mostimportant function of the Golgi apparatus. They add carbohydrate to protein and lipids to form glycoprotein and glycolipids.4. Formation of cell wall: The dictoysomes forms a structure called phragmoplast between the dividing plant cells. Phragmoplast form new cell wall between dividing cell.