Assertion: nucleolus's structure | /r/CapableOf | bound to protein
Facets:
Source sentences:
text: Within the nucleus of a cell, the main structures are: the nucleolus, an optically dense region, sphere shaped region, which contains concentrated ribosomal RNA (rRNA) bound to proteins (there may be more than one nucleolus in a nucleus); the chromatin, made of DNA molecules released into the nuclear matrix during cell interphase; and the karyotheca, or nuclear membrane, which is the membrane that encloses the nucleus.