Nuclear envelope

The nuclear envelope (also known as the nuclear membrane) is a double lipid bilayer that encloses the genetic material in eukaryotic cells. It separates the contents of the nucleus from the cytoplasm, and provides a barrier that helps to regulate the flow of molecules between these two compartments.

Structure

The nuclear envelope consists of two lipid bilayers—the inner nuclear membrane and the outer nuclear membrane. The space between these two membranes is called the perinuclear space, which is continuous with the lumen of the endoplasmic reticulum.

The outer nuclear membrane is continuous with the endoplasmic reticulum membrane, and is studded with ribosomes, which are involved in protein synthesis.

The inner nuclear membrane defines the boundary of the nucleus, and is lined by the nuclear lamina, a network of intermediate filaments that provide structural support to the nucleus.

Function

The nuclear envelope has several key functions:

• It acts as a barrier that separates the contents of the nucleus from the cytoplasm.
• It regulates the transport of molecules between the nucleus and the cytoplasm through nuclear pore complexes.
• It provides structural support to the nucleus through the nuclear lamina.

Nuclear Pore Complexes

Nuclear pore complexes are large protein complexes that span the nuclear envelope and allow for the transport of molecules between the nucleus and the cytoplasm. They are composed of around 30 different proteins, known as nucleoporins.

Diseases

Defects in the nuclear envelope are associated with a number of diseases, including progeria, Emery-Dreifuss muscular dystrophy, and laminopathies.

See also

• Cell nucleus
• Endoplasmic reticulum
• Nuclear pore
• Nuclear lamina

References

• 
  Diagram of a human cell nucleus
• 
  Nuclear envelope of one cancerous HeLa cell
• 
  Endomembrane system diagram
• 
  Nuclear envelope breakdown and reassembly in mitosis