GOLGI APPARATUs

STRUCTURE It was discovered by Camillo Golgi in1898 while he was investigating the nervous system. It looks like a stack of pancakes!

The Golgi apparatus is a “packing organelle”. It can be thought of as the “post office” of the cell. (It packages and labels items which it then sends to different parts of the cell).

Its made up of stacks of membrane-bound structures known as cisternae. (An individual stack is sometimes called a dictyosome) Vesicles from the endoplasmic reticulum Fuse with the network Go through the stack to the trans-Golgi network (where they are packaged and sent to their destination).

The cisternae stack has four functional regions. cis-Golgi network medial-Golgi endo-Golgi trans-Golgi network.

Function The Golgi apparatus modifies, sorts, and packs macromolecules made by the cell for cell secretion. It modifies proteins delivered from the rough endoplasmic reticulum. It also transports lipids around the cell, and creates lysosomes.

The Golgi plays an important role in the synthesis of: Enzymes in the cisternae are able to modify the proteins by adding carbohydrates and phosphates. The Golgi imports substances (such as nucleotide sugars) from the cytosol. This may also form a signal sequence which determines the final destination of the protein. The Golgi plays an important role in the synthesis of: Proteoglycans (molecules present in the extracellular matrix of animals) Carbohydrates.

In the lumen, the molecules are modified, then sorted for transport. The vesicles that leave the rough endoplasmic reticulum are transported to the cis face of the Golgi apparatus. Here they fuse with the Golgi membrane and empty their contents into the lumen.  In the lumen, the molecules are modified, then sorted for transport.

Proteins that will go to areas of the cell (other than the endoplasmic reticulum or Golgi apparatus) are moved (towards the trans face) to a complex network of membranes and vesicles known as the trans-Golgi network. This area of the Golgi is where proteins are sorted and shipped.