Question

Briefly describe the structure and function of Golgi apparatus.

Answer 1

Golgi Apparatus Structure

• The Golgi apparatus is a major organelle in most of the eukarytoic cells.
• They are membrane bound organelles, which are sac-like. They are found in the cytoplasm of plant and animal cells.
• The Golgi complex is composed of stacks of membrane-bound structures, these structures are known as the cisternae. An individual stack of the cisternae is sometimes referred as dictyosome.
• In a typical animal cell, there are about 40 to 100 stacks. In a stack there are about four to eight cisternae.
• Each cisternae is a disc enclosed in a membrane, it possess special enzymes of the Golgi which help to modify and transport of the modified proteins to their destination.
• The flat sacs of the cisternae are stacked and is bent and semicircular in shape.
• Each group of stacks is membrane bound and its insides are separated from the cytoplasm of the cell.
• The interaction in the Golgi membrane in responsible for the unique shape of the apparatus.
• The Golgi complex is polar in nature.
• The membranes of one end of the stack is different in composition and thickness to the membranes at the other end.
• One end of the stack is known as the cis face, it is the 'receiving department" while the other end is the trans face and is the "shipping department". The cis face of the Golgi apparatus is closely associated with the endoplasmic reticulum.
• Golgi Apparatus Function

1. The cell synthesize a huge amount of variety of macromolecules. The main function of the Golgi apparatus is to modify, sort and package the macromolecules that are synthesized by the cells for secretion purposes or for use within the cell.
2. It mainly modifies the proteins that are prepared by the rough endoplasmic reticulum.
3. They are also involved in the transport of lipid molecules around the cell.
4. They also create lysosomes.
5. The Golgi complex is thus referred as post office where the molecules are packaged, labelled and sent to different parts of the cell.
6. The enzymes in the cisternae have the ability to modify proteins by the addition of carbohydrates and phosphate by the process of glycosylation and phoshphorylation respectively.
7. In order to modify the proteins the golgi complex imports substances like nucleotides from the cytosol of the cell. The modifications brought about by the golgi body might form a signal sequence. This determines the final destination of the protein.
8. The Golgi complex also plays an important role in the production of proteoglycans. The proteoglycans are molecules that are present in the extracellular matrix of the animal cells.
9. It is also a major site of synthesis of carbohydrates. These carbohydratres includes the synthesis of glycoasaminoglycans, Golgi attaches to these polysaccharides which then attaches to a protein produced in the endeoplasmic reticulum to form proteoglycans.
10. The Golgi involves in the sulfation process of certain molecules.
11. The process of phosphorylation of molecules by the Golgi requires the import of ATP into the lumen of the Golgi.