GOLGI APPARATUS

Camillo Golgi in 1898 discovered a reticular structure in the cytoplasm of nerve cells with the help of metal impregnation technique using silver nitrate for which he received the Nobel Prize. This structure was named as Golgi apparatus or Golgi complex after him. Golgi complex is located near thecell nucleus.

Golgi complex is structurally similar in both plant and animal cells, but in plant cells it is more evident and is called as dictyosomes which are stack-like or plate-like bodies. Animal cells contain comparatively much smaller number of Golgi apparatus than plant cells.

The Golgi complex consists of (a) stack of flattened sacs or cisternae (b) small rounded transport vesicles (c) larger vacuoles filled with amorphous or granular material.

The cistemae, which are flattened sac like vesicles of Golgi complex, are arranged in parallel series and are separated by a space of 20-30 nm. Cisternae are gently curved so that the Golgi bodies give a bow like appearance (Figure shown below). The convex side facing the endoplasmic reticulum is 'forming' or 'proximal'-face, whereas the concave side oriented towards cell surface is the 'releasing' or 'distal' face of the complex.

Small vesicles called transition vesicles are frequently seen lying between rough endoplasmic reticulum and the forming face. It is thought that these vesicles are formed from the ER and migrate to Golgi, where they form new cisternae, which get fused with existing cisternal membrane, and thus the growth of the organelle occurs. New cistemac are formed at the forming face to compensate for the loss of secretory vesicles of the releasing face. The transformation of membrane from one type to another is a step which leads to the formation of a vesicle. The chemical composition of Golgi complex is intermediary between ER and the plasma membrane.