Introduction of rough endoplasmic reticulum:
A subset of the endoplasmic reticulum, the rough endoplasmic reticulum (rough ER) is a component of the cell’s endomembrane system (ER). Specifically, proteins that need to be transported to other organelles inside the cell or secreted from the cell are of particular interest to this organelle. It is also responsible for protein synthesis, folding, and modification. Due to its intimate relationship with mitochondria, the rough ER also affects how the cell reacts to unfolded proteins and contributes to the triggering of apoptosis.
The presence of membrane-bound ribosomes, which give the rough ER its distinctive look under the electron microscope, is one of its defining characteristics. These ribosomes, which resemble studs, set the organelle apart from the ER’s smoother regions called the smooth endoplasmic reticulum. Polysomes, which are collections of ribosomes, are also used to make some proteins. The form of the rough ER can also be used to identify it; it frequently consists of flattened sac like structures that are twisted and originate close to the nucleus. The rough ER’s membranes are connected to the outer nuclear membrane, and its lumen is continuous with the perinuclear space.
Describe the rough endoplasmic reticulum’s structure.
Cisterns and sheets are the two morphologically distinct parts of the ER. The bulk of the rough endoplasmic reticulum is composed of sheets, a two-dimensional arrangement of flattened sacs that span the cytoplasm. These membranes include ribosomes as well as the translocon, a significant protein complex required for protein translation in the rough ER.
The presence of cytoskeletal components, notably microtubules, has a direct impact on the rough ER’s structure. The ER network collapses when the microtubule structure is momentarily disrupted, and it does not reconstruct until the cytoskeleton is restored. Changes in ER morphology also reflect modifications in the microtubule polymerization pattern. Furthermore, ribosomes can spread and create tubular cisternae when they separate from sheets of the rough endoplasmic reticulum.
It’s necessary to stabilize the high curvature on the edges of ER sheets. Reticulons and DP1/Yop1p, two proteins, is crucial for this stability. These proteins shape the lipid bilayer by forming oligomers, making them essential membrane proteins. They also employ a structural motif that is placed into one membrane leaflet, causing it to become more curved. Since the overexpression of one protein seems to make up for the absence of the other protein, these two groups of proteins are redundant.
Explain the function of the rough endoplasmic reticulum.
Within the cell, the rough endoplasmic reticulum performs a variety of functions, most of which are connected to protein production. Polypeptides are created, altered, folded correctly into three dimensions, and either designated for secretion or sorted towards an organelle. Additionally, it is crucial for regulating how cells react to stress and ensuring proper protein folding through quality control.
The ratio of tubules to sheets changes in cells as the quantity of unfolded proteins rises. The need for the unique proteome of the rough ER may be reflected in this, or it may result from the larger area accessible within the sheets of the rough ER to rescue unfolded protein. The proteome of the rough ER reflects the unique function it plays in the cell. It has enzymes that bind to and alter RNA and are used in the metabolism of RNA. Since the organelle is involved in the translation of RNA into a protein, this is essential.
A developing polypeptide contains proteins that recognize different signal sequences and facilitate the translocation of those sequences. Important proteins within this organelle include glycosylation enzymes and proteins that serve as molecular chaperones to ensure the proper folding of the produced polypeptides. The ER will occasionally trigger apoptosis when there is too much-unfolded protein present inside the cell. In conjunction with mitochondria, this function is mediated.
What is the significance of the rough endoplasmic reticulum?
In the synthesis of proteins intended for cell secretion, the rough endoplasmic reticulum is crucial. As a result, it is covered in ribosomes and polysomes, which are responsible for translating the mRNA that encodes these proteins.
Hardin, J., Bertoni, G., & Becker, W. M. (2018). Becker’s world of the cell. Pearson.