Large subunit

The ribosome reads the messenger RNA (mRNA) into a specified string of amino acids, which grow into long chains that fold to form proteins. The large subunit (“60S” in eukaryotes) catalyzes peptide bond formation during translation.

Small subunit

A ribosome is an intercellular structure made of RNA and protein, and it is the site of protein synthesis in the cell. Ribosomes contain two different subunits, of which the small subunit (“40S” in eukaryotes) decodes the genetic message.