How does protein biosynthesis occur in a living cell?
Why do we need proteins
We all know how important proteins are for a living organism, because it is from them that the tissues of our body are built. The overwhelming majority of biochemical reactions in it are catalyzed by proteins (enzymes). These complex substances are part of the cell membranes (transport) and provide protection for the whole body against foreign agents (immunoglobulins).With them, we digest food (digestive enzymes) and move (muscle proteins), they work in the circulatory system, providing blood clotting, and are the product of the endocrine system, regulating all processes in the body.
How does protein and where it is created
The protein molecule consists of organic compounds - amino acids. Each cell of the body must be able to produce protein for both its own needs and the entire body. The process of this "production" is called protein biosynthesis. Where does it go inside the living cell?In order to create protein molecules, each smallest particle of the body has “protein-synthetic stations” - ribosomes.These are small intracellular organelles, their only function is protein biosynthesis. They do this quite effectively: one ribosome creates a protein chain of 20 amino acids in one second.In order to combine these individual acids with an amino group into a long protein molecule with unique specific properties, it is required to know how many molecules of a particular type need to be joined in a strict order. Where does the ribosome all this "known"? All information about how protein biosynthesis should take place in a cell is “recorded” in the nucleus of the latter, encoded in a giant DNA molecule - the focal point of all the genetic information of a living organism. That is why protein biosynthesis begins in the central organelle, the nucleus. The first stage of this process takes place there - copying information for transferring it to the ribosomes.
Stages of protein biosynthesis
To proceed with the assembly of the protein molecule, as already mentioned, the ribosome must receive information on how to do this, and the amino acids from which it will “construct” the protein. The whole process begins with the "rewriting" of information about the structure of the future protein molecule from DNA to messenger RNA (i-RNA). The latter in a eukaryotic cell undergoes processing - maturation.It consists in the formation of a shorter molecule by "cutting out" non-informative sections. The next stage is also characteristic only for the eukaryotic "living matter unit" - the transfer of i-RNA from the nucleus to the cytoplasm. In parallel, in the latter, transport RNA (t-RNA) is bound by enzymes to the corresponding amino acid. Finally, the next step is the translation - this is, in fact, protein biosynthesis occurring on the ribosome. The final stage of the entire complex process is the "maturation" of the protein. It acquires the desired secondary and tertiary structure, non-protein components are added to it (for example, heme, metal molecules, lipids, nucleotides, vitamins). The "ready" protein molecule is used by the cell or is released from it.