Ribosomes are primarily made of ribosomal RNA (rRNA). Along with ribosomal proteins, rRNA forms the two subunits of the ribosome and provides the catalytic core for protein synthesis. Key points

• rRNA is the main RNA component of ribosomes and acts as the structural framework and the ribozyme that catalyzes peptide bond formation during translation.

• In prokaryotes, the ribosome consists of 16S rRNA in the small subunit and 23S/5S rRNAs in the large subunit, combined with numerous ribosomal proteins. In eukaryotes, the subunit rRNAs are 18S (small) and 28S, 5.8S, and 5S (large), also assembled with ribosomal proteins.

• mRNA and tRNA are also involved in translation, but they are not the structural core of the ribosome; rRNA is the predominant RNA component and essential for its function.

If you’d like, I can pull up more detailed sources or diagrams showing the specific rRNA species in different organisms.