Ribosomes are cytoplasmic organelles found in all living cells and serves as the site of biological protein synthesis. It comprises of a complex molecular machine. The function of ribosomes is to link amino acids in a specific order that is specified by a messenger RNA molecule. This organelle has two subunits that are small and large subunits. Small subunit reads the RNA while a large subunit joins amino acids to form a polypeptide chain.

The subunits of ribosomes consist of one or more ribosomal RNA and ribosomal proteins. Ribosome and associated molecules are also known as translational apparatus.

Discovery of ribosomes

Ribosome was first discovered in 1950 by cell biologist Palade with the help of an electron microscope. In the electron microscope, these organelles appear as a dense particle. The name ribosome was coined by Richard B Robert to this dense particle at the end of 1950.

What is the structure of the ribosome?

The ribosome is a very complex structure largely made up of ribosomal RNA and ribosomal proteins. The RNA and proteins are arranged into two pieces of ribosomes known as the large and small subunits of the ribosomes. Both subunits of the ribosomes fit together.

Eukaryotes have the 80s ribosomes while the prokaryotes have the 70s ribosomes. In eukaryotes, the ribosome is located in the cytosol.

Ribosomes classification

Ribosomes are classified into two classes that are free and membrane-bound. Both are similar in structure but they differ only due to their distribution.

Free ribosomes

The free ribosome is excluded from the cell nucleus but can move freely in the cytosol.  The proteins that are formed by the free ribosome are released into the cytosol of the cell and used within the cell.

Membrane-bound ribosome

In some organelles of the cell when ribosomes synthesized proteins they become membrane-bounded. The ribosomes present in the rough endoplasmic reticulum are membrane-bounded.

Ribosomes size

The ribosome is made up of two subunits of different sizes due to which they are a little longer in the hinge than a diameter. Ribosome very in size between prokaryotic and eukaryotic cells.

The prokaryotic ribosome is of the 70s size made by 30s and 50s subunits. The prokaryotic ribosome is about 20nm in diameter. The prokaryotic ribosome consists of 65% ribosomal RNA and 35% ribosomal proteins.

Eukaryotic ribosome is of the 80s size that is made by 40s and 60s subunits. Eukaryotic ribosome is about 25 to 30nm in diameter.

What are the Locations of a ribosome?

Ribosomes are organelles present in both animal and plant cells. They are present in the cytosol in free form or in membrane-bounded form.

What are the Functions of ribosomes?

There are many functions of the ribosomes but the main function of it is to bring amino acids together to form specific proteins. These proteins are important for various cell activities. Proteins are used by the cell in many cases such as fixing the damage or directing the chemical process occurring in the cells. Membrane-bounded ribosomes are present in the endoplasmic reticulum.

Ribosomes synthesize proteins. Proteins are synthesized in two steps that are translation and transcription.


The making of messenger RNA from the DNA is known as transcription. DNA is present in the cell nucleus while proteins are synthesized in the cytosol of a cell, therefore, there must be an intermediate structure that mange proteins biosynthesis. And the intermediate is a messenger RNA.

The process of transcription completes in three steps that are initiation, elongation, and termination.

Once the messenger RNA is made they are modified after which it is able to leave the nucleus and enter to the cytosol.


The translation is the process in which proteins are made from the messenger RNA. The process of translation requires a translator and a substrate. These both are provided by the ribosome.

What are the specialized ribosomes?

There are mainly two types of ribosomes that are prokaryotic and eukaryotic ribosomes. However, there is also a specialized type of ribosome that is present that is known as the heterogeneous ribosome. The heterogeneous ribosome has a different composition, and structure and thus perform different activities compared to a typical ribosome.

Ribosome Biogenesis

The process of making the ribosome is known as ribosome biogenesis. In prokaryotes, ribosome biogenesis takes place in the cytoplasm while in eukaryotes it takes place in the cytoplasm and in the nucleus.

This process is tightly regulated and is linked to cell growth and divisions.

What is ribosomopathy?

these are a collection of disorders that occurs due to the abnormalities in the structure and functions of different kinds of ribosomal content. This collection of disorders is involved in muscle atrophy and underpins.

Some of the ribosomopathies at
1. DBA1
2.  DBA2
3.  DBA3
4.  DBA4
5.  DBA5
6.  DBA6
7.  DBA7
8.  DBA8
9.  DBA9
10.  DBA10
11.  DBA11
12.  DBA12
13.   DBA13
14.   DKCX
15.   TCS
16.   SDS
17.   CHH
18.   NAIC
19.   ICAS
20.   BWCNS
21.   CHARGE
22.   ACES


Ribosomes are cell organelles that are present in both prokaryotic and eukaryotic cells. Ribosomes are present in the cell in two forms that are free form or in membrane-bound form. The membrane-bound ribosome is found in the endoplasmic reticulum. Eukaryotic ribosome is of the 80s size while the prokaryotic ribosome is of 70s size. The function of the ribosome is to synthesize proteins that are needed for various cellular activities. Ribosomes are classified into two classes that are free ribosomes and the membrane-bound ribosome. Heterogeneous ribosomes are specialized ribosome that is different in structure and composition and perform different activities from the typical ribosome.  Ribosomes synthesize proteins. Proteins are synthesized in two steps that are transcription and translation. The making of messenger RNA from the DNA is known as transcription. As we know that DNA is present inside the nucleus and proteins are synthesized outside the nucleus, therefore, the cells need an intermediate and intermediate is the messenger RNA. The translation is the process in which proteins are made from the messenger RNA. The messenger RNA comes out of the nucleus and ribosome attached to it. After attachment, the ribosome units decode the messenger RNA and synthesize new proteins through various mechanisms. Abnormalities in these organelles can cause a huge disturbance in the cell.