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Tiny particle, the site of protein synthesis, that is present in large numbers in living cells. They occur both as free particles within cells and, in eukaryotes, as particles attached to the membranes of the endoplasmic reticulum. They are 40% protein and 60% RNA. Ribosomes account for a large proportion of the total RNA of a cell. Proteins newly formed on ribosomes detach and migrate to other parts of the cell to be used.
This entry comes from Encyclopædia Britannica Concise. For the full entry on ribosome, visit Britannica.com.