Golgi complex: –
- Camillo Golgi first observed densely stained reticular structure near the nucleus in nerve cell . These were later named Golgi bodies after him.
- Golgi body is pleomorphic, i.e. it is morphologically different in different types of cells.
- Golgi apparatus is surrounded by a differentiated region of cytoplasm where ribosomes, glycogen, and organelles such as mitochondria and chloroplasts are scarce or absent. This is called zone of exclusion
- It is only organ having definite polarity.
- Other names of Golgi body is Golgi complex, Golgiosome, Golgi bodies, Golgi material, Golgi membrane, Dalton complex, Lipochondria, Dictyosome (in plant cell), Trophospongium, baker’s body, Idiosome.
- Baker stained it with SUDAN BLACK dye and related it with secretion
- Golgi body is also named as “director of macromolecular traffic in cell, middle man of cell or traffic police”.
Structure : –
- Cisternae: They are membrane lined curved but flattened saccular which occur in a stack of 6-8. They are stacked parallel to each other. Varied number of cisternae are present in a Golgi complex. (In insect up to 30 cisternae). Curvature gives polarity to cisternae. The cisternae of Golgi body have four structural component Cis Golgi, endo Golgi, medial Golgi, Trans Golgi
- Tubules: They are short, branched, structure which are interconnected and formed on sides of cisternae.
- Vesicles: These are small sacs which develop from tubules. Vesicles are of two types:
(i) Transitional vesicles are small membrane limited
vesicles which are thought to form as blebs from the transitional ER to migrate and converge to cis face of Golgi, where they coalasce to form new cisternae.
(ii) Secretory vesicles contain secretory products.
(iii) Clathrin-coated vesicles are known to play a role in intra-cellular traffic of membranes and of secretory products.
Cis and Trans face of Golgi: –
- The Golgi cisternae are concentrically arrange near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face.
- The cis and the Trans faces of the organelle are entirely different, but interconnected. The Golgi apparatus principally perfumes the function of packaging materials, to be delivered either to the intra-cellular targets or secreted outside the cell.
- Materials to be packaged in the form vesicles from the ER fuse with cis face of the Golgi apparatus and move towards the maturing face.
- Secretion: Golgi apparatus receive various substances from endoplasmic reticulum through its cis face. These substance are chemically modified by enzyme Glycosyl transferease. E.g. Glycosylation of protein and lipids is completed in Golgi body.
- Lysosome formation: they are formed by Golgi body maturing face, rich in acid phosphatase
- Protein sorting: All secretory protein firstly transported to Golgi then Golgi decide its destination i.e. lysosome, plasma membrane
- In plants Golgi bodies synthesize complex polysaccharide of plant wall.
- O-linked glycosylation of protein occurs in Golgi complex sugar is added generally on threonine and serine.
- Golgi receive the membrane from SER and transform it into various specialized membrane of other organelles.
- During plant cell division Phragmoplast is formed by fusion of vesicles formed by Golgi body.
- Acrosome of sperm in modification of Golgi body.
- Helps in formation of cortical granules of egg.
Enzyme of Golgi Body:
Molecular Biology of the Cell-Alberts
Cell and Molecular Biology Concepts and Experiments.Geraldkarp
Cell Biology, Genetics, Molecular Biology, Evolution and Ecology by Verma, Agarwal