sentence: Ribosomes are molecular machines that synthesize proteins.
sentences_before: The 'nucleolus' is the part of a cell where ribosomes are made.
sentences_after: Viewed through a microscope, the nucleolus appears as a dark spot inside of the cell's nucleus. It is made up of dense DNA, RNA and proteins. The nucleolus is in the center of the nucleus.
concept_name: ribosome
headings: Nucleolus
categories: Organelles