Question

Describe the role of vesicles in the transport process between the nucleus, endoplasmic reticula, and the golgi apparatus.

Answer 1

The synthesis of molecules in the cell is completed only when they are targetted to their requisite site. In order to properly place the molecules to their correct places, the cells have developed a system of orgenelles and membranes called the GERL system. This GERL system includes golgi apparatus, endoplasmic reticulum and the lysosomes. In order to understand the interaction of various molecules synthesized, say in the nucleus, packaged and transported to their requisite site, the following steps can be followed with the example of a nasent polypeptide:

1. The mRNA synthesized in the nucleus is transported into the cytoplasm and it reaches the endoplasmic reticulum.
2. The synthesis of appropriate polypeptide along with a leader sequence occurs on the ribosomes on the rough endoplasmic reticulum.
3. The nascent polypeptide is lead to the golgi apparatus under the influence of the leader sequence.
4. As the nascent polypeptide reaches the cis-face of the golgi apparatus, it gets internalized in the golge membranes and it is packaged into a small vesicle.
5. The engulfed polypeptide undergoes glycosylation and other modifications in the golgi.
6. The engulfed polypeptide then is pinched off from the trans-face of the golgi apparatus from where it is tranported either inside the cell only or outside the cell. The location of transporation depends upon the nature of the protein and the type of modification.
7. If the protien is mis-folded or undergoes any deterioration, it is transported into the lysosomes where it is digested and re-cycled.

Thus, the nascent polypeptide is tranported to its desired location following the GERL system.