Ribosome Structure Functions and Types


Ribosome is granular structure found in all cells (universal cell body). Firstly observed by George Palade.  Absent in mature RBC. it is a smallest organelles of the cell about 15-20nm in size.

  1. Prokaryotic : – 70s type. Made up of the 50s and 30s subunit.
  2. Eukaryotic : – 80s type. Made up of the 60s and 60s subunit.
  3. Mitochondrial and Chloroplast : – 70s type. Made up of the 50s and 30s subunit.

Presence in a cell: –
Present on RER with help of Ribophorin. Freely found in cytoplasm all present in the nucleolus of the cell.
Structure of  : –
According to sedimenting, there is two subunit of it. The Larger subunit is dome in shaped and smaller in ovoid.
Larger subunit has three sites: –

  1. A-site: – Aminoacyl or Acceptor site for t-RNA
  2. P-site: – Peptidyl site, Site for peptide chain elongation.
  3. E-site: – Exit site for t-RNA

Two subunits combine with the help of Mg2+ concentration. When the concentration of Mg2+ is 10 times more than subunit combines each other.
Larger subunit also contains the peptidyl transferase enzyme (Ribozyme).

Ribosomal subunits are made by riboprotein and r- RNA
50s subunit- 34% Protein + 23s and 5s r-RNA
30s subunit- 21% Protein + 16s rRNA
60s subunit– 40% Protein + 28s, 5.8s and 5s r-RNA
40s subunit- 33% Protein + 18s rRNA
Formation: –
It are formed in nucleolus by 40-60% protein and 60-40% r RNA.  The nucleolus is considered a ribosome producing factory.
 Functio: –
Ribosome takes part in protein synthesis so it is known as “engine of cell or protein factory of the cell.”
Polyribosome- during protein synthesis many ribosome attached to m-RNA known as polyribosome or polysome.

For hindi information of ribosome

BSER books
NCERT books
Molecular Biology of the Cell-Alberts
Cell and Molecular Biology Concepts and Experiments.Geraldkarp
Cell Biology, Genetics, Molecular Biology, Evolution and Ecology by Verma, Agarwal

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