Question

When the protein comes out of the ribosome it may not be finished. What else may be needed to be done to the protein and how is it done? (Hint, chaperones, sugars and more.)

Answer 1

Based upon the presence of granules, which are studded with ribosomes, it is of two types, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

The proteins that are intended to be secreted out of the cell are synthesized by the ribosomes of the RER. This system contains “cisternae.” They are the fluid-filled sacs, into which the synthesized proteins are released.

They modify these proteins by different processes. They enter into the endoplasmic reticulum as the lipid end of the protein (first 30 amino acids are hydrophobic) is attracted by the lipid component of the endoplasmic reticulum. Once they are in the ER, the hydrophobic chain is removed by the enzymatic process.

The secretory proteins are transported to the Golgi apparatus for further modification. For example, the glycosylation of the proteins by the addition of carbohydrates. The proteins are differentiated based on their functions and destination. These products are packaged in vesicles and transported to their destinations.

The folding of proteins (polypeptides) is facilitated by a class of molecules used by the cell when proteins are first produced or are undergoing renaturation. These facilitators of protein folding are called molecular chaperones. These molecular chaperones are the proteins that facilitate the folding and unfolding of proteins and assembly and disassembly of other macromolecular structures.