nuclear envelope
A double-membrane structure that surrounds the nucleus
of a eukaryotic cell. The parallel nuclear
membranes are separated by a narrow space (40–70 nanometers wide)
known as the perinuclear cisterna. The nuclear envelope
has many pores in its surface which regulate the flow of macromolecules
into and out of the nucleus. Each of the nuclear pores has a diameter of
about 70 nm (but an effective diameter for transport of only about 10 nm)
and is enclosed by single layered diaphragm of protein.
The outer membrane of the nuclear envelope is covered with ribosomes
and is continuous with the rough endoplasmic
reticulum (RER). It reforms the RER after cell
division. Related category
• CELL
BIOLOGY
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