Where does protein synthesis occur? The essence of the process and the place of protein synthesis in the cell

The process of protein biosynthesis is extremely important for the cell. Since proteins are complex substances that play a major role in tissues, they are irreplaceable. For this reason, a whole chain of processes of protein biosynthesis is realized in the cell, which occurs in several organelles. This ensures the cage reproduction and the possibility of existence.

The essence of the process of protein biosynthesis

The only place of protein synthesis is a rough endoplasmic reticulum. Here is the bulk of the ribosomes that are responsible for the formation of the polypeptide chain. However, before the translation stage (the process of protein synthesis) begins, activation of a gene in which information about the protein structure is stored is required. After this, it is required to copy this part of the DNA (or RNA, if bacterial biosynthesis is considered).

After copying DNA, the process of creating an information RNA is required. On its basis, the protein chain will be synthesized. And all the steps that occur with the involvement of nucleic acids, should occur in the nucleus of the cell. However, this is not the place where protein synthesis occurs. This is the location where preparation for biosynthesis is carried out.

Ribosomal protein biosynthesis

The main place where protein synthesis occurs is the ribosome, a cellular organelle consisting of two subunits. There are a lot of such structures in the cell, and they are mainly located on membranes of a rough endoplasmic reticulum. The biosynthesis itself occurs as follows: the information RNA formed in the cell nucleus exits through the nuclear pores into the cytoplasm and meets the ribosome. Then, the mRNA is pushed into the gap between the subunits of the ribosome, after which the first amino acid is fixed.

To the place where protein synthesis occurs, amino acids are supplied by transport RNA. One such molecule can only produce one amino acid once. They join in turn, depending on the sequence of codons of the information RNA. Also, the synthesis may stop for a while.

When moving along the mRNA, the ribosome can enter regions (introns) that do not encode amino acids. In these places, the ribosome simply moves along the mRNA, but no amino acids attach to the chain. Once the ribosome reaches the exon, that is, the site that encodes the acid, then it rejoins the polypeptide.

Post-Synthetic Modification of Proteins

After the ribosome reaches the stop codon of the information RNA, the process of direct synthesis is completed. However, the molecule obtained has a primary structure and can not yet perform the functions reserved for it. In order to function fully, the molecule must be organized in a specific structure: secondary, tertiary or even more complex - Quaternary.

Structural organization of the protein

Secondary structure is the first stage of structural organization. To achieve this, the primary polypeptide chain must be spiraled (form an alpha helix) or bent (create beta layers). Then, in order to occupy even less space along the length, the molecule is further tightened and rolled up into a tangle due to hydrogen, covalent and ionic bonds, as well as interatomic interactions. Thus, the globular structure of the protein is obtained .

Quaternary protein structure

Quaternary structure is the most complex of all. It consists of several sections with a globular structure, connected by fibrillar filaments of the polypeptide. In addition, the tertiary and quaternary structure may contain a carbohydrate or lipid residue, which extends the range of protein functions. In particular, glycoproteins, complex compounds of protein and carbohydrate, are immunoglobulins and perform a protective function. Also glycoproteins are located on cell membranes and work as receptors. However, the molecule is modified not where the protein synthesis occurs, but in a smooth endoplasmic reticulum. Here, it is possible to attach lipids, metals and carbohydrates to protein domains.