What is the role of cytoplasm in protein biosynthesis? Description, process and functions

The cell of any organism is one large factory for the production of chemicals. There are reactions on the biosynthesis of lipids, nucleic acids, carbohydrates and, of course, proteins. Proteins play a huge role in the life of the cell, because they perform many functions: enzymatic, signal, structural, protective and others.

Biosynthesis of protein: a description of the process

The construction of protein molecules is a complex multi-stage process that occurs under the influence of a large number of enzymes and in the presence of certain structures.

Synthesis of any protein begins in the nucleus. Information about the structure of the molecule is recorded in the DNA of the cell, with which it is read. Almost any organism's gene encodes one, only its inherent protein molecule.

What is the role of cytoplasm in protein biosynthesis? The fact is that the cytoplasm of the cell is a "pool" for monomers of complex substances, as well as structures that are responsible for the course of the protein synthesis process. Also, the internal environment of the cell has a constant acidity and ion content, which plays an important role in biochemical reactions.

The biosynthesis of the protein takes place in two stages: it is transcription and translation.

Transcription

This stage begins in the nucleus of the cell. Here, nucleic acids such as DNA and RNA (deoxy- and ribonucleic acids) play the main role. In eukaryotes, the transcriptional unit is a transcripton, and in prokaryotes such an organization of DNA is called an operon. The difference between transcription in prokaryotes and eukaryotes is that the operon is a region of the DNA molecule that encodes several protein molecules when the transcripton carries information on only one gene of the protein.

The main task of the cell at the stage of transcription is the synthesis of information RNA (mRNA) on the DNA matrix. For this, an enzyme such as RNA polymerase enters the nucleus. It participates in the synthesis of a new molecule of mRNA, which is complementary to the site of deoxyribonucleic acid.

For successful transcription reactions, the presence of transcription factors is necessary, which are also denoted by the abbreviation TF-1, TF-2, TF-3. These complex protein structures are involved in the coupling of the RNA polymerase to the promoter on the DNA molecule.

Synthesis of mRNA is continued until the polymerase reaches the terminal region of the transcripton, which is termed the terminator.

The operator, as another functional area of transcripton, is responsible for inhibiting transcription or, conversely, for accelerating the work of RNA polymerase. Responsible for regulating the work of transcription enzymes are special protein-inhibitors or activator proteins, respectively.

Casting

After the mRNA was synthesized in the nucleus of the cell, it enters the cytoplasm. To answer the question about the role of cytoplasm in protein biosynthesis, it is worthwhile to disassemble in detail the further fate of the nucleic acid molecule at the stage of translation.

Translation takes place in three stages: initiation, elongation and termination.

First, the mRNA must attach to the ribosomes. Ribosomes are small non-membrane structures of the cell, which consist of two subunits: small and large. First, ribonucleic acid is attached to a small subunit, and then closes the entire translation complex so that the mRNA is inside the ribosome. Actually, this ends the stage of initiation.

What is the role of cytoplasm in protein biosynthesis? First of all, this is the source of amino acids - the main monomers of any protein. At the elongation stage, a gradual build-up of the polypeptide chain occurs, starting with methionine starting codon, to which the remaining amino acids are attached. The codon in this case is a triplet of nucleotides of the mRNA that encodes one amino acid.

At this stage another type of ribonucleic acids - transport RNA, or tRNA - is connected to work. They are responsible for the delivery of amino acids to the complex of ribosomes with mRNA by formation of the aminoacyl-tRNA complex. Recognition of tRNA occurs by the complementary interaction of the anticodon of this molecule with the codon on the mRNA. Thus, the amino acid is delivered to the ribosome and attached to the synthesized polypeptide chain.

The termination of the translation process occurs when the stop codon regions reach the mRNA. These codons carry information about the end of the peptide synthesis, after which the ribosome-RNA complex is destroyed, and the primary structure of the new protein enters the cytoplasm for further chemical transformations.

In the process of translation involved special protein factors of initiation of IF and elongation factors EF. They are of various types, and their task is to ensure the correct connection of RNA with ribosomal subunits, as well as in the synthesis of the polypeptide chain itself during the elongation phase.

What is the role of cytoplasm in protein biosynthesis: briefly about the main components of biosynthesis

After the mRNA exits the nucleus into the internal environment of the cell, the molecule must form a stable translational complex. What components of the cytoplasm should necessarily be present at the stage of translation?

1. Ribosomes.

2. Amino acids.

3. tRNA.

Amino acids - monomers of proteins

To synthesize a protein chain, the presence in the cytoplasm of structural components of a peptide molecule - amino acids. These low molecular weight substances in their composition have an amino group NH2 and an acid residue of COOH. Another component of the molecule - a radical - is a distinguishing feature of each individual amino acid. So what is the role of cytoplasm in protein biosynthesis?

AK occur in solutions in the form of zwitter ions, which are the same molecules that give up or take hydrogen protons. Thus, the amino group of amino acids is converted to NH3 +, and the carbonyl group is converted to COO-.

In total, 200 AK are found in nature, of which only 20 are white-forming. Among them, there is a group of essential amino acids that are not synthesized in the human body and enter the cell only with the accepted food, and the non-essential amino acids that the body forms independently.

All AKs are encoded by a codon that corresponds to three nucleotides of mRNA, and one amino acid can often be encoded with just a few such sequences. The methionine codon in pro and eukaryotes is the starting point, The biosynthesis of the peptide chain begins. The stop codons include UAA, UGA and UAH nucleotide sequence.

What are ribosomes?

How are the ribosomes responsible for the biosynthesis of proteins in the cell and what is the role of these structures? First of all, these are non-membrane formations, which consist of two subunits: large and small. The function of these subunits is the retention of the mRNA molecule between them.

In the ribosomes there are sites in which the mRNA codons fall. In total, between the small and large subunits, two such triplets can fit.

Several ribosomes can be aggregated into one large polysome, due to which the rate of synthesis of the peptide chain increases, and at the output, several copies of the protein can be obtained at once. This is the role of the cytoplasm in protein biosynthesis.

Types of RNA

Ribonucleic acids play an important role in all stages of transcription. There are three large groups of RNA: transport, ribosomal and information.

MRNA participate in the transmission of information on the composition of the peptide chain. TRNAs are intermediates in the transfer of amino acids to the ribosomes, which is achieved by the formation of the aminoacyl-tRNA complex. The addition of an amino acid occurs only in the complementary interaction of anticodon transport RNA with codon on the information RNA.

RRNA participate in the formation of ribosomes. Their sequences are one of the reasons why the mRNA is retained between the small and large subunits. Ribosomal RNAs are formed in the nucleoli.

The importance of proteins

The biosynthesis of proteins and its significance for the cell are enormous: most of the body's enzymes are of a peptide nature, thanks to proteins, substances are transported through the cell membranes.

Proteins perform a structural function when they are part of the muscle, nerve and other tissues. Signal role is to transmit information about the processes that occur, for example, when light falls on the retina of the eye. Protective proteins - immunoglobulins - are the basis of the human immune system.