Rough Endoplasmic Reticulum: Structure and Functions

He Rough endoplasmic reticulum Is an organelle found in the cells of eukaryotic organisms. It is formed by an interconnected network of flat bags or encapsulated tubes in the form of small bulky and flat bags. These membranes are continuous and attach to the outer surface of the nucleus of the cells.

The endoplasmic reticulum can be found in all Eukaryotic cells , Except for Red blood cells And sperm. It should be noted that eukaryotic cells are those that have a cytoplasm contained by a membrane and have a defined nucleus. These cells form the tissues of all animals and a wide variety of plants.

Rough endoplasmic reticulum

There are two types of endoplasmic reticulum, the rough and the smooth. The rough reticulum is enveloped by other organelles called Ribosomes , Which are responsible for synthesizing proteins.

This type of reticulum is especially prominent in certain cell types, such as hepatocytes, where protein synthesis occurs actively. (BSCB, 2015)

The rough endoplasmic reticulum has numerous functions within the cell. These functions include processing and transporting proteins. In particular, it is responsible for carrying these proteins to the Golgi apparatus. There are some other proteins, such as glycoproteins that move through the reticular membrane.

This rough reticulum is also responsible for marking the proteins it transports with a sequential signal endorsed inside the lumen. Other proteins are directed to the exterior of the reticulum so that they can be packaged in vesicles and expelled from the cell by means of Cytoskeleton .

In synthesis, the rough endoplasmic reticulum can be seen as the transport system used by eukaryotic cells to mobilize the proteins contained in them at the moment they need to be moved. Helping your synthesis, folding and quality control.

A cell can be defined as a set of membranes. In this way, the endoplasmic reticulum provides 50% of the membranes found in the cells of the animals. However, it also has a presence in plant cells and is essential for the manufacture of lipids (fats) and proteins.

Characteristics of the rough endoplasmic reticulum

Rough Endoplasmic Reticulum: Structure and Functions

There are two fundamental types of endoplasmic reticulum, the smooth and the rough. Both are membranes that perform very similar functions, however, the rough reticulum has a different shape because its surface is striated and is closer to the nucleus of the cell and the Golgi apparatus.

In this way, the rough reticulum has the appearance of small bulging discs, while the smooth one looks like a tubular membrane without stretch marks. What gives this appearance to the rough reticulum are the ribosomes that are adhered along its membrane (Studios, 2017).

The rough endoplasmic reticulum is an organelle that is present in all eukaryotic cells and whose main task is to process proteins and move them from the nucleus to the ribosomes along its surface.

While ribosomes must construct the amino acid chains, the reticulum is responsible for moving this chain into the cisternal space and the Golgi apparatus, where the more complex proteins can be terminated.

Both the animal and plant cells have the presence of both types of endoplasmic reticulum. However, these two types remain separate depending on the organ where the cell is located.

Since cells whose main function is the synthesis and production of proteins will have a larger rough reticulum, while those that are responsible for producing fats and hormones, will have a higher concentration of smooth reticulum.

It is believed that once the proteins are processed by the reticulum, they pass into the Golgi apparatus in small vesicles in the form of bubbles.

However, some scientists argue that the reticulum, the membrane of the cell nucleus and the Golgi apparatus are so closely located that these vesicles do not even exist, and the substances are simply filtered from one place to another within This resort.

Once the proteins pass through the Golgi apparatus, they are transported by the reticulum to the cytoplasm for use inside the cell.

Functions

Rough Endoplasmic Reticulum: Structure and Functions 1

The rough endoplasmic reticulum is an extensor organelle composed of flat, bulky and hermetic sacs located adjacent to the nuclear membrane.

This type of reticulum is called"rough"because it has a striated texture on its outer surface, which is in contact with the cytosol and the ribosomes.

Ribosomes adjacent to the rough endoplasmic reticulum are known as ribosomes attached to the membrane and are firmly attached to the cytosolic side of the reticulum. Approximately 13 million ribosomes are present in the rough endoplasmic reticulum of any liver cell.

In general, this type of reticulum is evenly distributed within any cell, however, it can be seen in a higher concentration near the nucleus and the Golgi apparatus of any eukaryotic cell. (SoftSchools.com, 2017)

Ribosomes

The ribosomes found in the rough endoplasmic reticulum have the function of making many proteins. This process is known as translation and takes place mainly in the cells of the pancreas and the digestive tract, places where a high volume of proteins and enzymes must be made.

The rough endoplasmic reticulum works in conjunction with the ribosomes attached to the membrane to take the polypeptides and amino acids from the cytosol and continue the process of making proteins. Within this process, the reticulum is responsible for giving a"tag"to each protein during the early stage of formation.

Proteins are produced by the plasma membrane, the Golgi apparatus, the secretory vesicles, the Lysosomes , Endosomes and the endoplasmic reticulum itself. Some proteins are deposited in the lumen or empty space inside the reticulum, while others are processed inside the reticulum.

In the lumen, the proteins are mixed with groups of sugars to form glycoproteins. Some may also be mixed with groups of metals during their passage through the endoplasmic reticulum, generating chains of polypeptides that bind to give rise to hemoglobin.

Protein folding

Within the rough endoplasmic reticulum lumen, the proteins are folded into biochemical units of complex architecture forms, which are encoded to make more complex structures.

Quality control of proteins

In the lumen, an exhaustive process of quality control of proteins also takes place. Each one is reviewed for possible errors.

In case of finding a poorly folded protein, the lumen will reject it and will not let it continue in the process of forming more complex structures.

Rejected proteins are stored in the lumen or are recycled and eventually re-decomposed into amino acids. For example, type A pulmonary emphysema is generated when quality control taking place in the lumen of the rough endoplasmic reticulum continuously rejects proteins that have not been correctly folded.

The poorly folded protein will result in an altered genetic message that will be impossible to read in the lumen.

This protein will never leave the lumen of the reticulum. Nowadays, studies have been conducted that relate this process with possible failures in the organism under the presence of HIV.

Quality control and cystic fibrosis

There is a type of cystic fibrosis that is generated when an amino acid (phenylamine) is missing at a specific place in the protein manufacturing process.

These proteins can work well without the amino acid, however, the lumen detects that there is an error in that protein and rejects it, preventing it from advancing within the formation process.

In this case, the patient with cystic fibrosis completely loses the ability to construct more elaborate proteins, since the lumen does not pass poor quality proteins (Benedetti, Bánhegyi, & Burchell, 2005).

From the reticle to the Golgi apparatus

In most cases, the proteins are transferred to the Golgi apparatus to be"finished". In this place they are transported to vesicles or possibly located between the surface of the endoplasmic reticulum and the Golgi apparatus. Once completed, they are sent to specific locations within the body (Rogers, 2014).

Structure

Structurally, the rough endoplasmic reticulum is a network of membranes that can be found anywhere in the cell and are directly connected to the nucleus.

The membranes are slightly different from one cell to another, since the cell's functioning determines the size and structure of the reticulum it needs.

For example, some cells such as prokaryotes, spermatozoa, or red blood cells do not have any type of endoplasmic reticulum.

The cells that synthesize and release a higher concentration of proteins and, on the other hand, need to have a larger endoplasmic reticulum.

This is clearly seen in cells of the pancreas and liver, where cells have a large endoplasmic reticulum to synthesize proteins (Inc., 2002).

References

  1. Benedetti, A., Bánhegyi, G., & Burchell, A. (2005). Endoplasmic Reticulum: A Metabolic Compartment. Siena: IOS Press.
  2. (November 19, 2015). British Society for Cell Biology. Retrieved from"Endoplasmic Reticulum"(Rough and Smooth): bscb.org.
  3. , T.G. (2002). Endoplasmic Reticulum. Retrieved from"Endoplasmic Reticulum: encyclopedia.com".
  4. Rogers, K. (December 12, 2014). Encyclopædia Britannica. Retrieved from"Endoplasmic reticulum (ER): global.britannica.com.
  5. com. (2017). SoftSchools.com. Retrieved from The Function of Endoplasmic Reticulum: softschools.com.
  6. A., A. (2017). Biology For Kids. Retrieved from"Endoplasmic Reticulum"- Wrapping it Up: biology4kids.com.


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