Ribosome Subunits:
Large (1) and small (2) subunit fit together.
The ribosomal subunits of prokaryotes and eukaryotes are quite similar. However, prokaryotes use 70S ribosomes, each consisting of a (small) 30S and a (large) 50S subunit, whereas eukaryotes use 80S ribosomes, each consisting of a (small) 40S and a (large) 60S subunit.[The unit S means Svedberg units, a measure of the rate of sedimentation of a particle in a centrifuge, where the sedimentation rate is associated with the size of the particle. Svedberg units are not additive - two subunits together can have Svedberg values that do not add up to that of the entire ribosome.]