Difference Between 70S and 80S Ribosomes

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About Ribosomes

Ribosomes are the particles present in the cells in large numbers and mainly serve as a site for protein synthesis. They are present as free particles in both prokaryotic and eukaryotic cells and also attached to the membrane of the endoplasmic reticulum in the case of eukaryotic cells. The Discovery of ribosomes was in the year 1955 by a Romanian-American cell biologist George E. Palade, during his discovery he found that ribosomes are associated with the endoplasmic reticulum in eukaryotic cells. 

Along with protein synthesis, they also function by binding to a messenger ribonucleic acid (mRNA) and decoding the information carried by the nucleotide sequence of the mRNA. The transfer RNA’s having amino acids, enters into the ribosomes at the acceptor site. Once after getting added up, it further adds amino acid to the growing protein chain on tRNA. 


Difference Between 70S and 80S Ribosomes

                    70S Ribosome

                  80S Ribosomes

They are majorly found in prokaryotic cells like bacteria and they are also found in a few eukaryotic cells. 

Majorly found in eukaryotic cells. 

They are found in free states inside the cytoplasm in prokaryotic cells, whereas in the case of eukaryotic cells they are found in few organelles like mitochondria and chloroplast. 

Mainly found in the cytoplasm or attached to the endoplasmic reticulum. 

Their synthesis mainly occurs inside the cytoplasm of prokaryotes. 

Their synthesis mainly occurs inside the nucleolus. 

Their smaller subunit is 30S and larger is 50S

Their smaller subunit is 40S and larger is 50s. 

They have 3 molecules of RNA.

They have 4 molecules of RNA. 

Their weight is approx 2.7-3.0 million Daltons.

Their weight is approx 4.0-4.5 million Daltons. 

Their sedimentation coefficient is 70. 

Their sedimentation coefficient is approx 80. 

There are about 55 protein molecules, with 34 in larger subunit and 21 in smaller subunit in 70s ribosomes. 

There are about 73 protein molecules, with 40 in larger subunits and 33 in smaller subunits. 

They have approx 8,000 amino acids. 

They have approx 16,000 amino acids. 

RNA-to-Protein ratio is 2:1. 

RNA-to-Protein ratio is 1:1. 

Antibiotics inhibit protein synthesis. 

Antibiotics do not inhibit protein synthesis. 

FAQ (Frequently Asked Questions)

1. Explain the Functioning of Ribosomes?

Ans. Some of the important functions of ribosomes are discussed below:

1. Their major function is assembling amino acids for the formation of protein which is essential to carry out cellular functions.

2. Synthesis of mRNA from DNA by the process of DNA transcription. 

3. Synthesis of mRNA in the nucleus and its transportation to the cytoplasm is done by ribosomes for the synthesis of protein. 

4. Synthesis of protein with the help of tRNA, as the ribosomal subunits in the cytoplasm, are bound around mRNA polymers. 

5. Synthesis of protein occurs in the cytoplasm and is utilised in the cytoplasm itself whereas the protein which is synthesised by bound ribosomes are exported outside.  

2. Explain the Composition of Ribosomes?

Ans. Ribosomes are composed of two subunits, they are:

A. The small ribosomal subunits- these subunits read the mRNA. 

B. the large ribosomal subunits- these subunits mainly help in  the formation of polypeptide chains of amino acids.