Ribosomes are molecular machines found within all cells. They perform protein synthesis, translating instruction-sequences carried by
mRNA strands into proteins. The instructions carried by the
mRNA strands have been read from the cell's DNA strand by other molecular machines, in a process known as
transcription.
With the help of
tRNA molecules, ribosomes link
amino acids together in the order specified by the codons of messenger RNA (
mRNA) molecules. When strung together in the specified order, the
amino acids form polypeptide chains (unfolded protein molecules). These, in turn form all biological components, including the molecular machines found within cells.
Ribosomes consist of two major components: the small and large ribosomal subunits. These come together when needed to convert
mRNA instruction strands into unfolded proteins.
Ribosomes and their associated molecules are sometimes referred to as the translational apparatus.