Life is a process of existence of protein molecules.That's about it are expressed by many scientists who believe that protein is the basis of all life.These statements are absolutely correct, because in these substances in the cell the highest number of basic functions.All other organic compounds play the role of energy substrates, and energy is again needed for the synthesis of protein molecules.
body's ability to synthesize protein
Not all existing organisms are able to synthesize proteins in the cell.Viruses and certain bacteria can not form proteins, and therefore are parasites give the desired substance from the host cell.Other organisms, including prokaryotic cells, capable of synthesizing proteins.All cells of humans, animals, plants, fungi, almost all bacteria and protists live due to the ability of the protein biosynthesis.This is required for the implementation of the structure-forming, protective, receptor, transport and other functions.
A milestone characteristic protein biosynthesis
protein structure encoded in a nucleic acid (DNA or RNA) as a codon.This is the hereditary information that is played each time a cell requires new protein substance.The beginning of the biosynthesis of a transmission of information to the nucleus of the need to synthesize a new protein already specified properties.
In response dispiralized portion of the nucleic acid, which is encoded in its structure.This location information is duplicated and transmitted to the RNA of the ribosome.They are responsible for the construction of the polypeptide chain on the basis of the matrix - messenger RNA.Briefly all stages of the biosynthesis as follows:
- transcription (step doubling portion of DNA encoded protein structure);
- processing (step of forming messenger RNA);
- translation (protein synthesis in the cell on the basis of the messenger RNA);
- post-translational modification ("maturation" of the polypeptide, forming the bulk of its structure).
Arrangement nucleic acid
entire protein synthesis in a cell is performed ribosome, and the information about the molecules contained in a nucleic acid (RNA or DNA).It is in the genes: one gene - a certain protein.Genes incorporated information about the amino acid sequence of the novel protein.In the case of the removal of the DNA genetic code is carried out in such a way:
- begins the release of the nucleic acid portion of the histone occurs despiralization;
- DNA polymerase doubles DNA segment that stores protein gene;
- double portion is the precursor messenger RNA that is processed with enzymes to remove the non-coding inserts (on the basis of his being a synthesis of mRNA).
Based proinformatsionnoy RNA is synthesized mRNA.It is already a matrix, then protein synthesis in the cell occurs on ribosomes (in the rough endoplasmic reticulum).
ribosomal protein synthesis
messenger RNA has two ends that are executed as 3`- 5`.Reading and protein synthesis on ribosomes starts with 5`kontsa and extends to the intron - a site that does not encode any of the amino acids.It is as follows:
- messenger RNA "strung" on the ribosome, adds the first amino acid;
- the ribosome moves along the mRNA by one codon;
- transfer RNA provides the required (encoded data codon mRNA) alpha-amino acid;
- amino acid is attached to the starting amino acid to form a dipeptide;
- mRNA then shifted again by one codon, a tray of alpha-amino acid is attached to the growing peptide chain.
As soon as the ribosome reaches the introns (non-coding inserts), messenger RNA simply moving on.Then, as you move the mRNA, the ribosome reaches again exon - site, a nucleotide sequence which corresponds to a specific amino acid.
From this place starts again monomer addition to the protein chain.The process continues until the occurrence of another intron or until the stop codon.Last stop synthesis of the polypeptide chain, after which the primary structure of the protein is considered complete and phase begins postsynthetic (posttranslational) modification of the molecule.
posttranslational modification
After translation protein synthesis takes place in tanks smooth endoplasmic reticulum.The latter contains a small amount of ribosomes.In some cells they may be absent in the RES.Such sites are needed for secondary education first, then to the tertiary or, if programmed, the quaternary structure.
entire protein synthesis in the cell takes place with the expenditure of huge amounts of energy ATP.For all other biological processes needed to maintain protein biosynthesis.In addition, some of the energy needed to transport proteins in the cell active transport.
Many of the proteins are transferred from one cell to another location to be modified.In particular, post-translational protein synthesis occurs in the Golgi, where a particular polypeptide or carbohydrate structure joins lipid domain.
