Composition of Eukaryotic Ribosomes

The basic features of eukaryotic ribosomes are similar to those of bacterial ribosomes, except for their larger size. They contain a greater number of proteins (about 80) and an additional RNA molecule. 

A typical eukaryotic ribosome has a sedimentation coefficient of about 80 and consists of two subunits 408 and 608. These sizes may vary by as much as 10% from one organism to another in contrast with the homogeneity of bacteria ribosomes. The components of the subunits of eukaryotic ribosomes are as follows  

40S subunit one 18S rRNA molecule + 30-35 proteins 60S subunit one 5S, one 5.8S, and one 28S rRNA molecule 

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Whereas a prokaryotic ribosome has a sedimentation coefficient (see Topic G9) of 70S and subunits of 30S and 50S, a eukaryotic ribosome has a sedimentation coefficient of 80S with subunits of 40S and 60S (see Topic G9). The composition of eukaryotic ribosomal subunits is also more complex than prokaryotic subunits (see Topic G9) but the function of each subunit is essentially the same as in prokaryotes. 

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