* Ribosomal RNA (rRNA): This is a type of RNA that is specifically involved in protein synthesis. It provides the structural framework for the ribosome and also plays a role in the catalytic activity of the ribosome.

* Ribosomal proteins: These are proteins that bind to the rRNA and help to shape the ribosome and stabilize its structure. They also help to regulate the ribosome's activity.

The combination of rRNA and ribosomal proteins forms the two subunits of a ribosome:

* Small subunit: This subunit binds to the mRNA and initiates protein synthesis.

* Large subunit: This subunit contains the active site for peptide bond formation, which is where amino acids are joined together to form a protein chain.

These two subunits come together during protein synthesis to form a functional ribosome.