Eukaryotic cells have the compartmentalized genetic material, that is, it is surrounded by a membrane called a library that separates it from the cytoplasm. The synthesis of proteins in this cell happens as follows:
Protein synthesis is a rapid process that occurs in all cells of the body, more precisely ribosomes, organelles found in the cytoplasm and the rough endoplasmic reticulum. This process can be divided into three steps:
1. Transcript
The message contained in the cistron (portion of the DNA that contains the genetic information needed for protein synthesis) is transcribed by messenger RNA (mRNA). In this process, the bases are similar: DNA adenine binds to RNA uracil, DNA thymine with RNA adenine, DNA cytosine with RNA guanine, and so on, with RNA enzyme intervening. -polymerase. The sequence of 3 nitrogenous bases of mRNA forms the codon, responsible for the coding of amino acids. Thus, the mRNA molecule replicates the DNA message, migrates from the nucleus to ribosomes, crosses the pores of the plasma membrane and forms a template for protein synthesis.
2. Activation of Amino Acids
At this stage, transporter RNA (tRNA) acts, which takes the amino acids dispersed in the cytoplasm from digestion to the ribosomes. In one of the regions of tRNA is the anticodon, a sequence of 3 bases complementary to the mRNA codon. The activation of amino acids is given by specific enzymes, which attach themselves to the carrier RNA, which forms the aa-tRNA complex, giving rise to the anticode, a trio of codons complementary to the mRNA codons. For this process to take place there must be power, which is provided by the ATP.
3. Translation
In the translation phase, the message contained in the mRNA is decoded and the ribosome uses it to synthesize the protein according to the given information.
Ribosomes are formed by two subunits. In the smaller subunit, it binds to mRNA, in the larger subunit there are two sites (1 and 2), where each of these sites can join two tRNA molecules. An enzyme present in the larger subunit makes the peptide link between amino acids, the carrier RNA returns to the cytoplasm to join another amino acid. And so, the ribosome goes through the mRNA and causes the link between amino acids.
The process is terminated when the ribosome passes a stop codon and no tRNA enters the ribosome because they no longer have complementary sequences to the stop codons. Then, the ribosome is released from mRNA, the specific protein is formed and released from the ribosome.
To form a 60 amino acid protein, for example, it takes 1 mRNA, 60 codons (each corresponding to one amino acid), 180 nitrogenous bases (each sequence of 3 bases yields one amino acid), 1 ribosome and 60 tRNAs (each tRNA carries an amino acid). It can be noted, then, that this is a highly complex process, as there is the intervention of several agents.
