What is a ribosome?

A ribosome is a 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 the codons of a messenger RNA (mRNA) molecule. They 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 ribosomal proteins. The ribosomes and associated molecules are also known as the translational apparatus.