Question

Descrribe the Steps in protein synthesis associated with RER.

Answer 1

Protein synthesis in the RER involves the assembly of a ribosome-SRP complex, pausing of elongation, binding to the RER membrane, translocation of the growing polypeptide into the RER lumen, cleavage of the signal peptide, and folding and modification of the polypeptide. The RER also synthesizes phospholipids for cellular membranes.

Step-by-step explanation:

Steps of Protein Synthesis in the Rough Endoplasmic Reticulum (RER)

The process of protein synthesis associated with the RER involves several key steps:

1. An SRP (signal recognition particle) binds to the hydrophobic signal peptide of the nascent polypeptide.
2. Protein elongation is temporarily halted until the SRP-ribosome complex locates and binds to the RER membrane.
3. The ribosome-SRP complex attaches to an SRP receptor on the RER membrane, initiating translocation.
4. The SRP detaches from the growing polypeptide chain, allowing for its recycling.
5. Translation elongation resumes through a translocation channel within the RER.
6. A signal peptidase within the RER membrane cleaves the signal peptide co-translationally.
7. The growing polypeptide chain enters the RER lumen and begins to fold into its correct three-dimensional structure.

Ribosomes synthesize proteins and transfer them into the lumen of the RER where they undergo structural modifications, such as folding or the addition of side chains. These modified proteins are then incorporated into cellular membranes or secreted from the cell. Besides proteins, the RER is also responsible for the synthesis of phospholipids for the cell membrane.