Ribosomes | Class 11 Biology

The basic structural and functional unit of life is the cell. It is responsible for performing essential functions of life. All organisms, including plants, and animals, are made up of cells. Some of them are composed of a single cell known as unicellular organisms, while others are composed of many cells known as multicellular organisms.

In the human body, a lot of cells make up a tissue and multiple tissues make up an organ many organs create an organ system, and many organ systems functioning together make up the human body.

Types of Cell

Cells that have membrane-bound nuclei are called eukaryotic cells, whereas cells that lack membrane-bound nuclei are prokaryotic cells. 

Ribosomes

Ribosomes are the protein synthesizers of the cell.

• Ribosomes are granular structures and were first observed by George Palade (1953) under the electron microscope.
• A ribosome is a kind of complex molecular machine present inside the living cells that produce proteins from amino acids during a process of protein synthesis also called translation, and it translates genetic information stored in messenger RNA into proteins. 
• Ribosomes are specialized cell organelles and are found in both prokaryotic and eukaryotic cells. 
• Ribosomes are found inside the cytosol of the cell.
• Ribosomes are composed of two subunits – smaller and larger.
• The mRNA binds and is decoded in the smaller subunit and the amino acids get added in the larger subunit. Both the subunits contain protein and ribonucleic acid components.
• These subunits are joined to each other by the interactions between proteins in one subunit and rRNAs in the other subunit.

The word ribosome is made from taking ‘ribo’ from ribonucleic acid and ‘soma’ is the Latin word for body.  

Ribosomes Function

Ribosomes produce proteins from amino acids during a process of protein synthesis also called translation, and it translates genetic information stored in messenger RNA into proteins. 

• The DNA produces mRNA by the process of DNA transcription.
• The mRNA is synthesized in the nucleus and transported to the cytoplasm for the process of protein synthesis.
• The ribosomal subunits in the cytoplasm are bound around mRNA polymers. 
• The tRNA synthesizes proteins.
• The proteins synthesized in the cytoplasm are utilized in the cytoplasm itself, the proteins synthesized by bound ribosomes are transported outside the cell.

Types of Ribosomesthe 

	70’s Ribosomes	80’s Ribosomes
1.	These are found both in prokaryotes  and eukaryotes.	They occur in eukaryotic cells.
2.	They are found freely inside the cytoplasm of prokaryotes and matrix of plastids and mitochondria of eukaryotes.	They are found inside the cytoplasm of eukaryotes either freely or attached to ER.
3.	The sedimentation coefficient is 70.	The sedimentation coefficient is 80.
4.	They are comparatively smaller in the ength of (200—290 A) and diameter of (170— 210 A).	They are larger in the length of (300—340 A) and breadth (200—240 A).
5.	They are lighter, 2.7—3.0 million Daltons.	They are heavier, 4.0—4.5 million Daltons.
6.	The two subunits are the 30S and 50S.	The two subunits are the 40S and 60S.
7.	They are synthesized in the cytoplasm of prokaryotes and matrix of semi-autonomous cell organelles.	They are synthesized inside the nucleolus.
8.	It contains about 55 protein molecules, 34 in the larger subunit and 21 in the smaller subunit.	It contains about 73 protein molecules, 40 in the larger subunit and 33 in the smaller subunit.
9.	The ribosomes contain more rRNA than protein (60:40).	The ribosomes possess less rRNA as compared to protein (40: 60).

FAQs on Ribosome

Question 1: What are Ribosomes?

Answer:

A ribosome is a complex molecular machine found inside the living cells that produce proteins from amino acids during a process called protein synthesis or translation and it translates genetic information stored in messenger RNA into proteins.

Question 2: State Ribosomes Function.

Answer:

Ribosomes assemble amino acids to form proteins that are essential to carry out cellular functions such as damage repair and other chemical processes.

Question 3: How are prokaryotic ribosomes different from eukaryotic ribosomes?

Answer:

• Prokaryotic ribosomes contain three individual rRNA molecules and also contain the large ribosomal subunit i. e. 80s.
• Eukaryotic ribosomes contain four individual rRNA molecules and also contain the small ribosomal subunit i. e. 70s.

Question 4: Name two subunits of 70’s Ribosomes.

Answer:

The two subunits are the 30S and 50S.

Question 5: Where are the 70’s Ribosomes synthesized?

Answer:

They are synthesized in the cytoplasm of prokaryotes and matrix of semi-autonomous cell organelles.

Question 6: Where is the Ribosome located in a cell?

Answer:

Ribosomes are found inside the cytosol of the cell.