Describe the similarities and differences 3 or 4 complete se

Describe the similarities and differences (3 or 4 complete sentences) in the synthesis “pathway” (i.e. all the organelles and cellular components involved) between a protein that is NOT secreted (i.e., functions within the cytoplasm) versus a protein that IS secreted

Solution

The process of protein synthesis and secretion starts from the endoplasmic reticulum. The polypeptide chain is formed in the ribosomes, and then transferred to the Golgi apparatus, where the final modifications are done. The Golgi apparatus sorts the modified poly peptide molecules and packages into new transport vesicles which reach their particular destinations.

The proteins that are intended to be used within the cell (intracellular proteins) are produced by the ribosomes that float freely in the cytoplasm.

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. The proteins generally contain endoplasmic reticulum signal sequence at their N-terminus, which directs them to the rough endoplasmic reticulum. 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. From the trans-Golgi vesicles, proteins move to cell membrane through small transportation vesicles (exocytosis). Some of then may be degraded by lysosomes as a part of regulation of gene expression.