In biology, Many times we hear the word ribosome related to the translation of genes, RNA, proteins and others. However, it is difficult to understand all this operation without being clear about the basic concepts. That is why we are going to dedicate this article to explain what a ribosome is.
To achieve this, we will talk a little about their function and about the ribosomes of bacteria. In addition, we will discuss what they produce and where they are found. If you are interested in the subject or simply want to know what a ribosome is, this is undoubtedly the right article.
What is a ribosome and its function?
When we speak of ribosomes, we refer to cytoplasmic organelles that are not delimited by a membrane of rRNA (ribonucleic acid) and ribosomal proteins. Together they constitute a molecular machine found in all cells, with the exception of sperm. Thanks to them it is possible to carry out the necessary translation for the expression of genes. In other words: Ribosomes are responsible for protein synthesis through the information contained in DNA. This arrives transcribed to the ribosome in the form of mRNA (messenger RNA).
As for the function of the ribosome, it is the translation or synthesis of proteins. In order to carry out this task, ribosomes obtain the necessary information from the mRNA, since its nucleotide sequence will eventually determine the amino acid sequence of the protein. Regarding the RNA sequence, it comes from the transcription of a DNA gene. Transfer RNA is responsible for the transport of amino acids to ribosomes.
What do ribosomes produce?
The function of the ribosome is fundamental in the genetic code. As we have said previously, it is responsible for protein synthesis, a process also known as gene translation. To do this, the ribosome reads the information from the mRNA and incorporates the amino acids of the transfer RNA into the protein that is currently growing. Therefore, the ribosome produces proteins.
Before continuing we must know that amino acids make up proteins. Currently 20 amino acids have been discovered among all living things. In the genetic code, amino acids are encoded by codons, which are triplets of nucleotides. There are 64 codons that code for all amino acids and three signals to stop translation. Therefore, the code is degenerate and several different codons serve the same amino acid.
Ribosome: Protein Synthesis or Translation
Generally, the translation process begins with the AUG codon, which is responsible for coding for the amino acid called methionine. The codon that marks the end of the protein is the stop codon. As in most organisms, each codon codes for the same amino acid, the genetic code is considered universal.
Two parts of the ribosome come out of the cell nucleus: The minor and major subunits. These are held together by charges. When the magnesium concentration (Mg2+) decreases, both subunits tend to separate.
What are the ribosomes of bacteria?
We will first explain well what bacteria are before talking about their ribosomes. As well, they are prokaryotic unicellular living organisms, that is, they have no nucleus. To get a better idea: the genetic material of bacteria, which would be a double-stranded circular DNA molecule, is free within the cytoplasm and is not enclosed in a nucleus as is the case with eukaryotic cells.
When we look at bacteria under a microscope, they look like rods, spirals, or balls. Despite what almost everyone believes, most of them are not harmful. Less than one percent of bacteria cause disease. In fact, they are essential to the ecosystems that exist on earth.
Bacterial ribosomes continue to perform the same function: Protein synthesis. Only, this time, it takes place in bacteria. It is an essential process for its growth.
There are a total of three phases that bacterial growth goes through. We are going to comment on them below to better understand the fundamental role of the ribosome in this case.
- Lag phase / Adaptation phase: A population of bacteria needs an adaptation time when it is in a new environment that provides the necessary nutrients for its growth. In this case, growth is slow while the cells prepare to initiate rapid growth. Furthermore, it involves a high rate of protein biosynthesis, where ribosomes come into play.
- Exponential phase: During this phase, cell growth is rapid and exponential. The nutrients are metabolized at the highest possible speed until they are exhausted, giving way to the third and final phase.
- Stationary phase: In the stationary phase, cells drastically reduce their metabolic activity and begin to use non-essential cellular proteins as an energy source. This is a transition period from rapid growth to a stress response state. In it, the expression of genes related to DNA repair, nutrient transport and antioxidant metabolism is activated.
Thus, without ribosomes, bacteria could not even start their growth.
Where are ribosomes found?
There are different places where ribosomes are found: In the rough endoplasmic reticulum, in mitochondria, in chloroplasts, and in the cytosol. However, they can only be seen using an electron microscope, since their size is 32 nanometers in the case of eukaryotic cells and 29 nanometers in prokaryotic cells. When viewed under an electron microscope, they are round in shape and electron-dense. On the other hand, under an optical microscope it is seen that they are responsible for the basophilia of some cells.
I hope this article has clarified for you what a ribosome is and what its function is. The world of biology and genetics is vast and new things are being discovered every time. In order to understand them, it is worth having some basic knowledge such as knowing what gene translation is and how it works.