One of the most important tasks of any living cell is making the
protein molecules that form its internal structures, trigger
important chemical reactions, and fill many other roles. How are
protein molecules made?
Protein molecules are assembled from simple molecules called amino
acids by molecular machines called ribosomes, themselves made largely
out of protein. A ribosome starts making a protein by catching the
end of a molecule called messenger RNA, which contains the coded
instructions to make the protein.
The messenger RNA (which was created by reading DNA in the cell's
nucleus) feeds through the ribosome like a ribbon, and as it feeds
through its code is read. The ribosome recognizes the pattern of
code, and adds the appropriate amino acids to the partially completed
protein. When the protein molecule is finished, it is released and
the ribosome can begin building another one.