The ribosome (/ˈraɪbɵˌzoʊm/) is a large and complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis (translation). Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules.Ribosomes consist of two major components: the small ribosomal subunit, which reads the RNA, and the large subunit, which joins amino acids to form a polypeptide chain.Each subunit is composed of one or more ribosomal RNA (rRNA) molecules and a variety of proteins.he sequence of DNA encoding for a protein may be copied many times into RNA chains of a similar sequence. Ribosomes can bind to an RNA chain and use it as a template for determining the correct sequence of amino acids in a particular protein.