Each ribosome having of two subunits a small subunit and a large subunit, every of that is a multi component complex of rRNAs (ribosomal RNAs) and ribosomal proteins that is given in the figure. One way of distinguishing between particles like as ribosomes and ribosomal subunits is to place the sample in a tube within a centrifuge rotor and spin this at very high speed. That causes the particles to sediment to the tube bottom. Particles which vary in mass shape and density sediment at variant velocities (sedimentation velocities). Thus a particle with double the mass of another will always sediment faster give both particles have the same density and shape.