The site of protein synthesis is ribosome.
It is found in 2 states;
1) free state: in this case it synthesised protein which is required inside the cell. The ribosome is dispersed in the cytoplasm.
2) attached state; in this case it is attached to RER by means of glucoprotein called ribozymes. The attached ribosome involves in the formation of protein required outside the cell.
Therefore ribosome is called the factory of protein while the factory of ribosome is nucleolus.
