To study the processes taking place in the body, you need to know what is happening at the cellular level. And there protein compounds play a crucial role. It is necessary to study not only their functions, but also the creation process. Therefore, it is important to explain protein biosynthesis briefly and clearly. Grade 9 is best suited for this. It is at this stage that students have enough knowledge to understand this topic.
Proteins - what it is and why they are needed
These macromolecular compounds play a huge role in the life of any organism. Proteins are polymers, that is, they consist of many similar “pieces”. Their number can vary from several hundred to thousands.
In a cell, proteins perform many functions. Their role is also great at higher levels of organization: tissues and organs largely depend on the proper functioning of various proteins.
For example, all hormones are of protein origin. But it is precisely these substances that control all processes in the body.
Hemoglobin is also a protein, it consists of four chains that are connected in the center by an iron atom. This structure provides the ability to carry oxygen by red blood cells.
Recall that all membranes contain proteins. They are necessary for the transfer of substances through the membrane of cells.
There are many more functions of protein molecules, which they perform clearly and implicitly. These amazing compounds are very diverse not only in their roles in the cell, but also in structure.
Where does the synthesis take place
The ribosome is an organelle in which the bulk of the process called "protein biosynthesis" takes place. Grade 9 in different schools differs in the program of studying biology, but many teachers give material on organelles in advance, before studying translation.
Therefore, it will be easy for students to recall the material they have learned and to consolidate it. You should know that on one organelle only one polypeptide chain can be created at a time. This is not enough to satisfy all the needs of the cell. Therefore, there are a lot of ribosomes, and most often they combine with the endoplasmic reticulum.
This EPS is called rough. The benefit of this “cooperation” is obvious: immediately after synthesis, the protein enters the transport channel and can be sent to the destination without delay.
But if we take into account the very beginning, namely, reading information from DNA, then we can say that protein biosynthesis in a living cell begins even in the nucleus. It is there that the messenger RNA is synthesized , which contains the genetic code.
Necessary materials - amino acids, the place of synthesis - ribosome
It seems that it is difficult to explain how protein biosynthesis proceeds, briefly and clearly, the process scheme and numerous drawings are simply necessary. They will help convey all the information, and students will be able to remember it easier.
First of all, synthesis requires “building material” - amino acids. Some of them are produced by the body. Others can only be obtained with food, they are called indispensable.
The total number of amino acids is twenty, but due to the huge number of options in which they can be arranged in a long chain, protein molecules are very diverse. These acids are similar in structure, but differ in radicals.
It is the properties of these parts of each amino acid that determine which structure the resulting chain will “fold” into, whether it will form a quaternary structure with other chains, and what properties the resulting macromolecule will possess.
The process of protein biosynthesis cannot simply proceed in the cytoplasm, it needs a ribosome.
This organelle consists of two subunits - large and small. At rest, they are disconnected, but as soon as synthesis begins, they immediately connect and begin to work.
Such different and important ribonucleic acids
In order to bring the amino acid to the ribosome, you need a special RNA called transport. To reduce it, t-RNA is designated. This single-chain clover leaf molecule is able to attach one amino acid to its free end and transfer it to the site of protein synthesis.
Another RNA involved in protein synthesis is called messenger (messenger). It carries an equally important component of the synthesis - a code that clearly states when which amino acid to cling to the protein chain formed.
This molecule has a single-stranded structure, consists of nucleotides, as well as DNA. There are some differences in the primary structure of these nucleic acids, which you can read about in a comparative article on RNA and DNA.
Information about the composition of the protein m-RNA receives from the main custodian of the genetic code - DNA. The process of reading deoxyribonucleic acid and synthesizing mRNA is called transcription.
It occurs in the nucleus, from where the resulting m-RNA is sent to the ribosome. DNA itself does not leave the nucleus, its task is only to save the genetic code and pass it to the daughter cell during division.
Summary table of the main participants of the broadcast
In order to describe protein biosynthesis briefly and clearly, a table is simply necessary. In it we will write down all the components and their role in this process, which is called translation.
What is needed for synthesis | What role does |
Amino acids | Serve as a building material for the protein chain |
Ribosomes | Broadcast venue |
t-RNA | Transports amino acids to ribosomes |
m-RNA | Delivers information on the sequence of amino acids in a protein to the synthesis site |
The process of creating a protein chain itself is divided into three stages. Let's look at each of them in more detail. After that, you can easily explain to everyone the protein biosynthesis briefly and clearly.
Initiation is the beginning of the process.
This is the initial stage of translation in which the small subunit of the ribosome binds to the very first t-RNA. This ribonucleic acid carries an amino acid - methionine. Translation always begins with this amino acid, since the starting codon is AUG, which encodes this first monomer in the protein chain.
In order for the ribosome to recognize the start codon and not start synthesis from the middle of the gene, where the AUG sequence may also appear, a special nucleotide sequence is located around the initial codon. It is from them that the ribosome recognizes the place where its small subunit should sit.
After complexing with m-RNA, the initiation step ends. And the main stage of the broadcast begins.
Elongation - the middle of synthesis
At this stage, a gradual build-up of the protein chain occurs. The duration of elongation depends on the amount of amino acids in the protein.
First of all, a large subunit of the ribosome joins. And the initial t-RNA is in it entirely. Outside, only methionine remains. Next, the second t-RNA carrying another amino acid enters the large subunit.
If the second codon on m-RNA coincides with the anticodon at the top of the “clover leaf”, the second amino acid is attached to the first using a peptide bond.
After this, the ribosome travels exactly three nucleotides along the m-RNA (one codon), the first t-RNA detaches methionine from itself and separates from the complex. In its place is the second t-RNA, at the end of which two amino acids are already hanging.
Then the third t-RNA enters the large subunit and the process repeats. It will occur until the ribosome stumbles upon a codon in m-RNA, which signals the end of translation.
Termination
This stage is the last, to some it may seem very cruel. All the molecules and organelles that worked so smoothly to create the polypeptide chain stop as soon as the ribosome hits the terminal codon.
It does not encode a single amino acid, so no matter which t-RNA enters the large subunit, they will all be rejected due to mismatch. Here termination factors come into play that separate the finished protein from the ribosome.
The organelle itself can either decompose into two subunits, or continue its path through m-RNA in search of a new start codon. Several ribosomes can be located on one mRNA at once. Each of them is at its own stage of translation. Just created protein is supplied with markers, with the help of which everyone will understand its destination. And on EPS it will be sent where necessary.
To understand the role of protein biosynthesis, it is necessary to study what functions it can perform. It depends on the sequence of amino acids in the chain. It is their properties that determine the secondary, tertiary, and sometimes quaternary (if it exists) protein structure and its role in the cell. More information about the functions of protein molecules can be found in the article on this topic.
Learn more about broadcasting.
This article describes protein biosynthesis in a living cell. Of course, if you study the subject more deeply, explaining the process in full detail will take many pages. But the above material should be enough for a general idea. Video materials in which scientists modeled all the stages of the translation can be very useful for understanding. Some of them are translated into Russian and can serve as an excellent manual for students or just an educational video.
In order to better understand the topic, you should read other articles on related topics. For example, about nucleic acids or about the functions of proteins.