The cells are small factories with different activities completed by cellular organelles, small units within these cells. On this occasion we are going to deal with ribosomes, important macromolecules related to genetic expression. Continue reading this Ecology Verde article so that you know in depth that are the ribosomes, its function and structure so that you understand the functioning of the cells.
What are ribosomes
The ribosomes They are cellular organelles being willing In the cytoplasm inside the cellboth eukaryotic and prokaryotic. They are abundant in all cells. In blood erythrocytes there are very few and are absent in mature sperm. Some of the characteristics of the ribosomes are:
- Have globular form and They have no membrane.
- They are part of the cell machinery for Manufacture proteinstarting the process with a molecule of genetic information and translating it to another for such information to materialize.
- Its composition It is based on ribosomal RNAhence his name. In addition, they are also composed of ribosomal proteins. Discover the difference between DNA and RNA, here.
Do not hesitate to take a look at this ecology article see on cellular organelles: what are, functions and examples to have more information on the subject.
Types of ribosomes
Ribosomes can be classified into various types. We can find different types of ribosomes according to their disposal and according to the type of cell to which they belong. In this way, we find the following ribosomes classification.
Types of ribosomes according to its location
The first classification responds to the arrangement of ribosomes. This location is going to Direct proteins elaborate to different sites. Thus, we have two types that are the following:
- Adhered ribosomes: These ribosomes are subject to the outside of the rough endoplasmic reticulum. They can also be subject to the outside part of nuclear membrane. These produce proteins that will be inserted in membranes or that will be for secretion.
- Free ribosomes in cytoplasma: They are free in the cytoplasm and can be individual or be united by RNA forming a chain.
These free ribosomes can be found in different areas. According to this characteristic, they can be classified in:
- Mitorribosomas: They are free in the mitochondrial matrix. Do not hesitate to consult this article about the mitochondria: function and structure of Ecology Verde.
- PLASORribosomas: They are free in the stroma of chloroplasts, in plant cells or algaras.
Types of ribosomes according to the cell type
They can also be classified according to the cell type. In this case there are the following types of ribosomes.
- Prokaryotic ribosomes: They are found in prokaryotic cells, or without true nucleus. They have a sedimentation level of 70s, smaller than eukaryotic ribosomes. Later we will deepen this measure. They are mostly composed of RNA, and less than half is composed of proteins.
- Eukaryotic ribosomes: They are the ribosomes that eukaryotic cells have, or with core. They have a larger level of sedimentation than prokaryotic ribosomes, being 80s. More than half is composed of proteins, and less than half by RNA. They are larger size than prokaryotic ribosomes.
Ribosomes function
Ribosomes are in charge of produce proteins and participate in the Cell genetic control. For this, Ribosoma follows the following steps:
- Get and read the information of the Messenger RNA.
- Translates such information to a amino acid sequence.
- The blocks are created that They form proteinsthat do not accommodate randomly, but occurs by default and orderly.
There are organs that produce large amounts of protein, so their tissue cells need to have several ribosomes. An example of this is the pancreas that produces insulin.
The correct activity of ribosomes is essential for organisms can fulfill their functions. When there are ribosomal alterations, diseases such as Diamond Blackfan or congenital disquesratosis can occur, which affects the tegumentary system and bone. These are very rare diseases, but that occur.
Ribosomes Structure
The ribosomes They are formed by two subunits And each of them is formed by RNA and ribosomal proteins, as we have mentioned at the beginning of the article. States two subunits of ribosomes are:
- The big subunit: It has a central bump and two sides, with a front and a back.
- The small subunit: The bumps of the big subunit help to insert the small subunit, which has only one head and a platform.
These subunits are measured with the sedimentation coefficient and They are expressed in the Svedbergs unitwhich refers to the speed with which a particle is sediment during the centrifugation. Depending on the type of cell in which the ribosome is found, this unit varies:
- In eukaryotic cells: The minor subunit is 40s and the largest is 60s.
- In prokaryotic cells: The minor subunit is 30s and the largest is 50s.
Said subunits They come together when they detect a messenger RNApositioning one above under the big one. Who detects it is the small subunit, and then the large subunit is coupled. With the help of the transfer RNA, it translates to the messenger RNA in a chain of amineosoacids that will form the proteins. The Small subunit is the one that links the arnt with the RNAm. The large subunit allows the links that unite the amino acids to form. The subunits are separated when they detect a completion sequence, which indicates that the protein is complete.
In the major subunit there are three sites or necessary clefts for transfer RNAs to be inserted and completed their protein translation process. Such sites are:
- Site A, or aminoacidal: Where the aminoacil arnt is inserted, which carries the first amino acid.
- P or peptide site: where the peptidil arnt is inserted, which carries the peptide chain and the proteins as a result.
- Site e: It is the final site, where the site P site moves and replaces the TRINT that was on this site.
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- Campbell, N. and Reece, J. (2006). Biology. Madrid: Pan -American Medical Editorial.
- Marcey, D. (2014). Introduction to the structure of the ribosome. Available at: http://biomodel.uah.es/model1j/rna-prot/ribosoma.htm
- Miguel Hernández University. (2006). General organization of cells: cytosol and endomembrane system. Available at: http://retina.umh.es/docencia/confsvivos/temas/tema_11_ribosomas.pdf