Rugged endoplasmic reticulum: what is and function

The rough endoplasmic reticulum (RER) is characterized by its structure formed by a Network of elongated tubules and flattened sackswhich are stacked more or less regular. These structures contain numerous Ribosomas attached to their membranes. The amount of associated ribosomes conditions the shape of the RER, that is why when the number of ribosomes increases, the tubules expand and adopt the form of flattened tanks.

The RER is present in all cells, except in erythrocytes. THE DISTRIBUTION OF THE RER varies according to the type of cell and its activity:

• In the glandular cells of pancreatic acinos, the RER adopts a folded sheet form in the basal part of the cell.
• In hepatocytes, forms the Berg bodies, which present a concentric disposition.
• In neurons, Nissl’s granules are formed, which are dyed with basic dyes.
• In plasmocytes, the RER is distributed throughout the cytoplasm and is around the nucleus.
• In little active cells, the RER is poorly developed and dispersed by the cytoplasm.

The main function of the rough endoplasmic reticulum is to be specialized centers in the Protein synthesisthis thanks to the ribosomes embedded in the organelle. Apart from protein synthesis, the RER has other important functions such as:

• Glycosylation: It is the main post-translational modification process experienced by proteins in the secretory route. N-glycosylation is essential for cell survival and plays a fundamental role in biological activity and the physical-chemical properties of proteins.
• Protein synthesis linked to the membrane by anchors with phospharyositol: Some proteins bind to the membrane using a GPI anchor. After the synthesis of the protein is completed, the precursor protein remains linked to the RER membrane through a C-terminal hydrophobic sequence of 15-20 residues of the peptide signal, while the rest of the protein is found in the lumen of the RER.
• Response to poorly folded proteins: The accumulation of poorly folded proteins in the lumen of the RER triggers an adaptive response known as the UPR (response to poorly folded proteins), which coordinates different cellular programs.
• Post-translational modifications: Among the post-translational modifications, covalent modifications are included to functional groups (R) and amino and carboxyl lateral chains.

The structure of the rough endoplasmic reticulum (RER) is characterized by being formed by an interconnected membranes network that form flattened sacks and tubules, distributed in the cytoplasm of the cell. These flattened sacks contain ribosomes attached to their surface, which gives rer a rough appearance when observed under a microscope.

Next, the RER structure is described:

• Membranes: The interconnected membrane network of the RER form flattened and tubules bags, and is composed of a lipid bilayer that contains various associated proteins and enzymes.
• Ribosomes: They are united to the outer surface of the RER. These ribosomes are arranged in the cytosolic face of the membrane, at an approximate distance of 15 nm between them. The union of ribosomes to the rough endoplasmic reticulum is given by subunit 60s, and is mediated by transmembrane glycoproteins, specifically ribophorin I and II.
• Tubules and tubules: The RER is organized in the form of a tanker, which are flat and elongated structures, and interconnected tubules. The tanks have a flattened shape, while the tubules are cylindrical and narrow.
• Lumen of the RER: It is the internal space surrounded by the rer membranes. In this lumen, important processes are carried out, such as folding and modification of newly synthesized proteins, before being transported to other parts of the cell.

Next, we present some of the main distinctions between them:

• Morphological characteristics: The rough endoplasmic reticulum (RER) exhibits a rough appearance under the electronic microscope due to ribosomes united to its external surface. On the other hand, the smooth endoplasmic reticulum lacks ribosomes and presents a smooth appearance in the electronic microscope.
• Primary functions: The RER is mainly involved in the synthesis and modification of protein, while the story plays a wide range of functions, such as lipid synthesis, cell detoxification, calcium storage and carbohydrate metabolism regulation.
• Cellular Location: The RER is commonly found in cells that synthesize and secrete large amounts of proteins, such as pancreatic cells or antibody producing cells. Instead, the relax is especially abundant in liver and muscle cells, where it performs specific metabolic functions.
• Composition and membrane structure: Both the RER and the REL are composed of lipid membranes and associated proteins, but the presence of ribosomes in the RER confers a distinctive structure and a different protein composition.

Now that you know what the rough endoplasmic reticulum is, you may be interested in this article about cellular organelles: what are, functions and examples.

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