What is a polysome, functions performed
Today we offer to talk about what polysome is. One very important life process takes place in every cell - it can be observed in the cells of absolutely any organism. What for? The fact is that the protein in the cell performs many functions. Among them:
- the formation of the skeleton of intracellular organelles and extracellular structures;
- cell membrane stabilization;
- enzymatic and so on.
Generally speaking, protein is the main class of cell organic matter, which performs a lot of necessary functions.
Ask why we suddenly started talking about protein and its importance for the cell? We are trying to answer the main question of the article - what is a polysome? The thing is that this structure is involved in the synthesis of such a necessary protein.
This structure of the cellular cytoplasm has a second name - the polyribosome.The fact is that polysomes consist of several ribosomes, which are interconnected by means of a matrix RNA molecule (if abbreviated, mRNA). As you already understood, further talk will be about ribosomes. Have to refresh a little memory.
In all cells, both prokaryotic and eukaryotic, there are mandatory structural units that are called ribosomes. What is it? Ribosomes are presented as tiny bodies consisting of two subunits. The main task of the ribosome is protein synthesis in translation. In addition, it is important to recall that ribosomes are non-membrane structures.
So what is polysome? This is a cell formation that consists of these very ribosomes. As mentioned earlier, the binding element is an RNA molecule (matrix or informational). Ribosomes are like beads impaled on this molecule. As a result, we get a temporary structure called polysome. Another important fact is that polysomes are concentrated in places where fast synthesis of large amounts of protein is needed. This is their main biological role.
Structure of the ribosome
We have considered what a polysome is (in biology it is an important temporary formation that is involved in protein synthesis), now we delve a little bit into its constituent parts, the ribosome. Consider their structure.
It can be said that a ribosome is a machine that can reproduce absolutely any kind of protein. Since they are identical in structure, perform a common function, have the same molecular composition, they are considered to be cellular organelles.
In the cytoplasm there is a mass of other organoids (for example, plastids, the cell center, and so on), but the main difference between ribosomes from them is the representation of a huge number in one cell. Immediately make a reservation that their cycle forms about a hundred million.
These organoids are complex ribonucleoprotein particles, which include:
- many individual proteins;
- several RNA molecules.
Ribosomes of prokaryotic and eukaryotic cells differ from each other, but have common principles of organization and functioning. Now we will highlight the differences between these organoids in different cells.
Ribosomes of prokaryotes and eukaryotes
We all know that there are two groups of organisms:
Their cell structure is different, so we can identify the difference between the eukaryotic and prokaryotic ribosomes. Thus, the structure of the policy they also unequal.
Let's start with prokaryotes. Here we can detect ribosomes 70S, which are formed using two subunits, large and small - 50S and 30S. The structure of the 50S subunit includes: 5S and 23S. As part of the 30S: 16S. What does this mysterious S mean? This is the rate of sedimentation of particles in a centrifuge. Bacteria in the cells can detect a very large number of polysomes, which is associated with the rapid process of protein synthesis.
Now eukaryotes. We can notice differences in the constant S. For these cells, the value is 80. It, in turn, consists of:
- the small subunit - 40S (includes 18S RNA);
- the big one is 60S (5S, 28S and 5.8S).
Despite these differences, in prokaryotic and eukaryotic polysome cells perform one important function - the acceleration of protein synthesis. As mentioned above, the highest rate and concentration of polysomes is observed in bacteria. Now it should be clear to you exactly what a polysome is. There is only one final point left - the functions performed by this structure.
The main function of the policy is translation. In this process, the formation of the primary structure of the protein. In total, there are three stages of polypeptide synthesis:
- initiation (at the moment the molecule of messenger RNA is attached to the ribosome);
- elongation (in other words, the growth of the polypeptide chain, at this stage the transport of amino acids to the ribosome takes place, and then the attachment by means of a peptide bond);
- termination (stop of protein synthesis and precipitation of the resulting polypeptide from the ribosome).
Now I want to summarize briefly. From this article it became clear to us what a polysome is and how it is formed. Once again, the polysome is a structural unit formed with the help of ribosomes. In addition, we clarified the main task of this structure. This is accelerated protein synthesis. It is worth remembering that polysomes are found in both prokaryotic and eukaryotic cells.