Home Science 40 Interesting Ribosome Facts: Structure, Production, Function

40 Interesting Ribosome Facts: Structure, Production, Function

by Sankalan Baidya
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Ribosome facts

What is Ribosome? What are its functions? In this article on Ribosome facts, we are going to find out the answers to these questions and in the process, we will learn everything about this interesting cell organelle. We will try to make it as robust as possible so that you can find the answers to all your questions. Of course, this article on facts about Ribosome will help you in your school homework as well. So, let us begin…

Interesting Ribosome Facts: 1-5 | What, Where, & How Many?

1. Ribosomes (singular: Ribosome) are cell organelles. This means, they are present inside a cell. We know that cell organelles have their predefined functions and hence, Ribosomes have their own functions as well.

2. Ribosomes are present in every single cell in this world. This means, they are present in both Eukaryotic cells as well as in Prokaryotic cells. Since Ribosomes are present in all Eukaryotic cells, they are present in both animal and plant cells. So, Ribosomes can be found even in human begins.

3. Now, Ribosomes are found inside a cell but exactly where do you find them? They are found free-floating in the Cytoplasm and they are also found attached to the Endoplasmic Reticulum.

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4. Even simple bacterial cells will have ribosomes. Put in short, they are present in single-celled organisms as well. Here is something really fascinating. Ribosomes are present separately inside Mitochondria (present in all Eukaryotic cells) and Chloroplasts (present in plant cells only).

5. Ribosomes are present in great numbers. In a single bacterial cell, there can be thousands of Ribosomes. In complex organisms such as humans, a single cell can have hundreds of thousands of Ribosomes. In case of frog ovum, there are hundreds of millions of Ribosomes.

Interesting Ribosome Facts: 6-10 | Structure of Ribosome

6. Ribosome has a very interesting structure. It is basically a complex of ribonucleoprotein or RNA-protein. As far as the size of Ribosome is concerned, it is anywhere between 20 and 30 nanometers.

7. A single Ribosome has two subunits. These two subunits are of different sizes and they have different functions. When the time for synthesizing new protein comes, the two fuse together in order to complete the process of protein production.

8. The two subunits of a Ribosome are known as Small Subunit and Large Subunit. Interestingly, an entire Ribosome and its two subunits have been assigned values. These values are known as Svedberg Value. Even more interesting, the sum total of the individual values of the two subunits never add up to the total value of the whole Ribosome. The values in case of Prokaryotic and Eukaryotic cells are given in the table below:

Elements Eukaryotic Cell Prokaryotic Cell
Whole Ribosome Value 80S 70S
Small Subunit Value 40S 30S
Large Subunit Value 60S 50S

‘S’ stands for Svedberg Value and depends on sedimentation rate of molecules of various shape and size instead of just molecular weight. This is the reason why the sum total of the individual values of the two subunits never add up to the total value of the whole Ribosome.

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9. A subunit of a Ribosome is made of ribosomal RNA (denoted as rRNA) and proteins. Just how many rRNA and proteins. The table below you tell you that in a structured way:

Elements Eukaryotic Cell Prokaryotic Cell
Small Subunit 1 rRNA and approx 31 proteins 1 rRNA and approx 21 proteins
Large Subunit 3 rRNA (one large and two small of varying sizes) and approx 49 proteins 2 rRNA (one small and one large) and approx 31 proteins

10. rRNAs are responsible for providing the majority of the mass of a Ribosome. The remaining mass comes from the proteins that attach themselves to various parts of rRNAs. In this context, it is important to say that a single rRNA has several self-complementarity regions. These are regions where a particular region of the rRNA can form a base pair with another region of the same rRNA, thereby creating interlinks. As a result of this highly structured RNA molecules are created which make up the Ribosome’s core.

Interesting Ribosome Facts: 11-15 | Ribosome Production

11. Now the most important question of all – ‘where are these Ribosomes produced?’ In case of Eukaryotic Cells, the study of the process of manufacturing Ribosomes is still under progress. From whatever we have learned so far, Ribosomes in Eukaryotic Cells are manufactured inside the nucleolus present inside the cell nucleus.

12. Since Ribosomes are made of rRNA and proteins, it is natural that proteins will be required for synthesis of Ribosomes. It turns out that the Ribosomes that stay scattered in the Cytoplasm of a cell are the ones that produce the proteins required by nucleolus for Ribosome synthesis.

13. Now, since the raw materials are produced outside the nucleus (and hence the nucleolus) they are transported inside the nucleolus. Inside the nucleolus, the proteins are used for assembling the rRNA (both small rRNA and large rRNA). This assembly pattern is provided by the genes that are present inside the nucleolus.

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14. Once the rRNAs (small and large) are produced they are combined with proteins to form what we call Small Subunit and Large Subunit. The subunits are then ejected out of the nucleolus and the nucleus. Once outside the nucleus, the rest of the assembling takes place, thereby finishing the synthesis of Ribosomes.

15. In a Prokaryotic Cell, the nucleus and hence the nucleolus is absent. So, how are ribosomes produced? In Prokaryotic Cells, this happens in the cytoplasm or cytosol at various dispersed sites. They have 20 operons (a functioning unit of genomic DNA with a gene cluster). These operons are the sites where rRNAs are transcribed. Then, there are 52 genes that are responsible for encoding Ribosomal proteins near the operons (sites of rRNA transcription). Then, the ribosomes are assembled in the cytosol using rRNAs and proteins.

Interesting Ribosome Facts: 16-20 | Ribosome Function (mRNA)

16. At the very beginning we said that Ribosomes manufacture proteins. These proteins that the Ribosomes produce are used by our body. If Ribosomes are absent, there will be no protein production and our bodies will come to a halt.

17. How does the protein manufacturing take place? This is really interesting. They do this by a process that is known as ‘Translation’. What do they translate?

18. They read and translate the information encoded in the mRNA or Messenger RNA. These mRNAs include the instructions template produced by the DNA. Once they read and translate the information, they produce the proteins as required.

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19. What is mRNA? mRNA is another type of RNA that is assembled inside the nucleus of the cell (Eukaryotic Cell). What happens is that a gene’s DNA has a complementary base-pairing template. There is an enzyme in the nucleus known as RNA polymerase II which acts as a catalyst for formation of what is known as pre-mRNA molecule. Once the molecule is produced, it is further processed to finally make the mRNA, which is basically a copy of the gene but as a single strand. This formation of mRNA inside the nucleus is known as ‘Transcription’.

20. Once Transcription is completed and mRNA is ready, it is sent out of the nucleus into the Cytoplasm where a Ribosome picks it up and reads the genetic information. This reading of the genetic information is known as ‘Translation’.

Interesting Ribosome Facts: 21-25 | Ribosome Function (mRNA and tRNA)

21. Once the Ribosome reads the mRNA, it produces the protein using amino acids. The amino acids are joined together by the Ribosome in the exact same pattern (template) that was inscribed on the mRNA.

22. What really happens when mRNA reaches the Cytoplasm? When the mRNA leaves the nucleus, the Small Subunit and the Large Subunit of a Ribosome will come together and unite. The mRNA will attach with the Small Subunit of a Ribosome which will actually perform the Translation job.

23. The question is, what will happen once the information in mRNA is read and translated? This is where you will need the amino acids for production of proteins. But, who will bring the amino acids? This job is done by tRNA or Transfer RNA.

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24. The tRNA is also produced inside the nucleus with another enzyme called RNA polymerase III where some heavy processing is required to create the final form of tRNA that is also used by the Ribosome to access the amino acids for protein building.

25. When the Small Subunit and the Large Subunit of the Ribosome unite, a tunnel is produced. The tRNA produced by the nucleus slides inside this tunnel. The tRNA has three binding sites known as A, P and E. A stands for aminoacyl-tRNA, P stands for peptidyl-tRNA and E stands for Exit binding site.

Interesting Ribosome Facts: 26-30 | Ribosome Function (Protein Formation)

26. Under the tRNA tunnel is a small groove positioned on the Small Subunit and Large Subunit boundary in such a way that the mRNA attached to the Small Subunit also attaches itself to the tRNA via that groove.

27. The tRNA brings amino acids and proteins from the Cytoplasm. They enter through the A site and at site P, the growing peptide chain is contained. Site E is from where used up tRNA molecule exits the Ribosome.

28. When the amino acids bind with each other forming the peptide chain, the tRNA takes translated information from mRNA and arranges and binds the amino acids accordingly so that the genetic code is now represented by proteins.

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29. Once the mRNA code says stop, the peptide chain is ready. It is then polymerized inside the Ribosome and eventually releases the polypeptide (polymerized peptide chain). The released polypeptide then goes to Cytoplasm in case of Prokaryotic Cells or in case of Eukaryotic Cells, it goes into Golgi Apparatus where protein formation is eventually completed.

30. The produced proteins will then either stay inside the cell or will go outside the cell depending upon the requirement.

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It is to be noted that protein formation in Prokaryotic Cells happen with a process called Coupled Transcription-Translation. Explaining this will require going into extreme details, which is clearly beyond the scope of this article and hence, we will skip it. But, remember that even in Prokaryotic Cells, mRNA and tRNA are involved in protein synthesis where transcribed information is translated to produce proteins that are eventually release in the cytoplasm.

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Interesting Ribosome Facts: 31-35 | Fun Facts and Ribosome Trivia

31. There are two types of Ribosomes. One type are those that float freely in the Cytoplasm. These Ribosomes don’t attach themselves with any other organelle.

32. Free-floating Ribosomes produce structural proteins, for instance, the type of proteins that body requires for hemoglobin production.

33. These free-floating Ribosomes are present in clusters of 5 or 10 floating in the Cytoplasm in types of cells that are known for growing rapidly, for instance, brain cells and pancreas cells. In those cells that do not grow rapidly, these free-floating Ribosomes do not form clusters. These Ribosome clusters are known as polyribosomes or polysomes.

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34. Yet another function of free-floating Ribosomes is that of manufacturing the proteins that are required to make up the Cytoplasm itself.

35. The other type of Ribosomes that one can find are the ones that attach themselves to an organelle called Endoplasmic Reticulum. These Ribosomes are meant for producing various types of enzymes in the body and are also responsible for making proteins that are used for making the Cell Membrane. The proteins that attached Ribosomes manufacture always move outside the cell.

Interesting Ribosome Facts: 36-40 | Fun Facts and Ribosome Trivia

36. Once a Ribosome produces a polypeptide, the two subunits of the Ribosome – the Small Subunit and the Large Subunit will separate from each other. When they separate, they will either be broken up or will be reused.

37. Ribosomes are also present inside Mitochondria (present in both animal and plant cells) and Chloroplast (present only in plant cells). However, the Ribosomes present inside Mitochondria and Chloroplast are similar to Ribosomes found in Prokaryotic Cells (that is, they are 70S Ribosomes).

38. Ribosomes are extremely efficient in the sense that in the Eukaryotic Cells, they are capable of adding up to 2 amino acids in a protein chain in a single second. In Prokaryotic Cells, their efficiency is far greater and are capable of adding up to 20 amino acids to a polypeptide (other way of saying protein chain) in a single second.

39. 4 different nucleic acid molecule types and 70 different protein types are used for making Ribosomes, making them incredibly complex cell organelles.

40. The method used by Ribosomes for protein synthesis in Prokaryotes is slightly different from the method used by Ribosomes for protein synthesis in Eukaryotes. It is this difference that allows us a microscopic opportunity window for making antibiotic drugs capable of attacking harmful microbes.

That concludes our list of Ribosome facts. We have tried to produce information in the simplest way we could while also being as exhaustive as possible. In case we have missed something or we have put in some incorrect information, feel free to let us know through the comments section.

Sources: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

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