Question

Some secretory proteins and some integral membrane proteins must pass through a membrane. A ribonucleoprotein known as the signal recognition particle (SRP) guides these proteins either to the plasma membrane (in bacteria) or the endoplasmic retriculum (in eukaryotes). Put the following steps of the membrane translocation of eukaryotic secretory proteins in order, starting after the signal peptide emerges from the ribosome and ending with the protein being transported by vesicles out of the endoplasmic retriciulurn. Signal peptide exits ribosome during translation. Translation resumes. Signal peptidase removes signal peptide from growing polypeptide. SRP binds to the signal peptide, and translation stops. Ribosome docks to a translocon. Growing polypeptide crosses the ER membrane through translocon. SRP moves the ribosome to the ER membrane. The remainder of the polypeptide is moved into the ER lumen. Protein is transported out of the ER.

Answer 1

Answer:

1- Signal peptide exits ribosome during translation

2- SRP binds to the signal peptide, and translation stops

3- SRP moves the ribosome to the ER membrane.

4- Signal peptidase removes signal peptide from growing polypeptide

5- Translation resumes

6- Ribosome docks to a translocon

7- Growing polypeptide crosses the ER membrane through translocon

8- The remainder of the polypeptide is moved into the ER lumen

9- Protein is transported out of the ER.

Explanation:

Synthesis of secretion proteins might start in the cytoplasm with the production of a molecule portion known as a signal sequence. When this signal sequence interacts with a signal recognition particle ,the polypeptide synthesis is temporarily stopped. This complex leads the synthesizing protein and associated ribosome to a specific region in the Rough endoplasmic reticulum where binds the signal recognition particle receptors in the endoplasmic reticulum membrane. Here the signal recognition particle gets separated from the complex, and the protein synthesis continues. The ribosome links to the endoplasmic reticulum membrane and the protein cross through a membrane pore called translocon. At this point, the protein is growing in the reticulum lumen.  Here it continues the protein building and also happens the protein folding and the initial stages of glycosylation.

Once proteins are synthesized in the endoplasmic reticulum, they are packaged and sent to the Golgi complex in vesicles, where it happens the final association of carbohydrates with proteins. Finally, protein is transported from the Golgi complex to its final destiny.