tuumamembraani

Tuumamembraani, also known as the nuclear envelope, is a double membrane that surrounds the nucleus in eukaryotic cells. It separates the contents of the nucleus, including the genetic material, from the cytoplasm. The nuclear envelope is composed of two lipid bilayers, an inner and an outer membrane, separated by a space called the perinuclear cisterna. The outer nuclear membrane is continuous with the endoplasmic reticulum and may be studded with ribosomes.

The nuclear envelope is perforated by nuclear pores, which are complex protein structures that regulate the transport of molecules between the nucleus and the cytoplasm. These pores allow for the selective passage of ions, small molecules, and larger macromolecules such as proteins and RNA. The nuclear envelope plays a crucial role in gene expression by controlling the movement of transcription factors into the nucleus and messenger RNA out of the nucleus.

The inner nuclear membrane is lined by the nuclear lamina, a meshwork of intermediate filament proteins (lamins) that provides structural support to the nucleus and plays a role in DNA replication and gene regulation. The nuclear envelope is essential for maintaining the integrity of the genome and for regulating cellular processes in eukaryotic organisms. It disassembles during mitosis and reforms around the separated chromosomes at the end of cell division.