process of protein biosynthesis is extremely important for the cell.Because proteins are complex substances that play a fundamental role in the tissue they are irreplaceable.For this reason, in a cell implemented whole process chain protein biosynthesis, which proceeds in several organelles.This ensures that the cell reproduction and the possibility of existence.
essence of the process of protein biosynthesis
only place of protein synthesis - a rough endoplasmic reticulum.Here is the bulk of ribosomes, which are responsible for the formation of the polypeptide chains.However, before the start step of translation (protein synthesis), requires activation of the gene, which stores information about the protein structure.After that you want to copy the given region of DNA (or RNA if treated bacterial biosynthesis).
After the DNA copying process requires the creation of messenger RNA.At its base will be carried out the synthesis of the protein chain.Moreover, all the steps that occur involving nucleic acids must occur in the cell nucleus.However, this is not the place where protein synthesis occurs.This location, which is preparing for the biosynthesis.
ribosomal protein biosynthesis
main place where protein synthesis occurs - is the ribosome, cellular organelle consisting of two subunits.Such cell structures in a huge amount, and they are mainly located in the membranes of the rough endoplasmic reticulum.Himself biosynthesis occurs as follows: in the cell nucleus formed messenger RNA goes through the nuclear pores into the cytoplasm and meets the ribosome.Then mRNA is pushed into the gap between the ribosome subunits, whereupon the fixation of the first amino acid.
to the place, where the protein synthesis, amino acids are fed with the help of transfer RNA.One such molecule can bear one single amino acid.They can be connected in turn depending on the sequence of codons of the messenger RNA.Also, the synthesis can be stopped for a while.
While moving along the mRNA ribosome can get into the space (introns) that do not encode amino acids.In these areas a ribosome moves along mRNA, but the addition of amino acids to the chain occurs.As soon as the ribosome reaches exon i.e. portion which encodes acid, then it rejoins the polypeptide.
postsynthetic modification of proteins
After reaching the stop codon of the ribosome messenger RNA synthesis process directly ends.However, the resulting molecule has a primary structure and is not reserved for it to perform functions.In order to properly function, the molecule must be organized in a specific structure: secondary, tertiary or even more complex - quaternary.
structural organization of the protein
Secondary structure - the first stage of the structural organization.To achieve the primary polypeptide chain should helical (alpha-helix form) or bend (create beta-layers).Then, in order to occupy even less space along the length of the molecule more pulled together and wound into a ball by hydrogen, ionic and covalent bonds and the interatomic interactions.Thus, a globular protein structure.
quaternary protein structure
quaternary structure is the hardest of all.It consists of several sections with globular structure, connected by threads fibrillar polypeptide.In addition, tertiary and quaternary structure may contain a carbohydrate or lipid moiety that extends the range of functions of the protein.Specifically, glycoproteins, complex compounds of a protein and a carbohydrate are immunoglobulins and perform a protective function.Also glycoproteins are located on cell membranes and work receptors.However, no modified molecule where protein synthesis occurs, and in the smooth endoplasmic reticulum.There exists the possibility of joining lipids, metals and carbohydrates to protein domains.