12.1 - The Nucleus of Eukaryotic Cell
- Enclosed by a complex nuclear envelope that forms a boundary between the nucleus
and the cytoplasm.
- Composed of
o Nucleoli (synthesis of ribosomal RNA and the assembly of ribosomes)
o Nucleoplasm - where the solutes of nucleus are dissolved
o Nuclear matrix - protein-containing fibrillar network.
- Consists of two cellular membranes arranged parallel to one another.
- Barrier that keeps ions, solutes and macromolecules from passing freely between the
nucleus and cytoplasm.
- 2 membranes fused at sites forming circular pores that contain complex assemblies of
- Outer membrane generally studded with ribosomes and is continuous with the
membrane of the rough ER.
- Space between membranes is continuous with the ER lumen.
Inner surface of the nuclear envelope is bound by integral proteins to a thin filamentous
meshwork nuclear lamina.
o Provides mechanical support to the nuclear envelope.
o Serves as site of attachment for chromatin fibers at the nuclear periphery.
o Roles in DNA replication and transcription.
o Composed of polypeptides called lamins.
Nuclear Pore Complex (NPC)