This type of protein is called Ribosome. The cytoplasmic ribosomes of eukaryotes are RNA/protein complexes(20nm diameter), whose function is the biosynthesis of proteins.
Composed of various of proteina and a type of RNA called ribosomal RNA (rRNA), ribosomes are complex structures containing two irregularly shaped subunits of unequal size.
They come closer to each other to form whole ribosomes when protein synthesis is initiated; when not in use, the ribosomal subunits separate. The number and distribution of ribosome in any cell
depend on the relative metabolic activity and the proteins being synthesized. Although eukaryotic ribosomes are larger and more complex than those prokaryotes, they are all similar in overall shape and function.
As we all know, this RNA-protein aggregates consists of 2 subunits. The small subunit called 30S in prokaryotes and 40S in eukaryotes.
As for the large subunit, it is called 40S in prokaryotes and 60S in eukaryotes. The small subunit has over 20 proteins and one strand of RNA whereas the large subunit has over 30 proteins and two strands of RNA.
Ribosomes has the structural role in protein synthesis due to presence of three different sites on its surface called the P, A and E sites.
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