kärnmembran

The kärnmembran, also known as the nuclear envelope or nuclear membrane, is a double membrane structure that surrounds the nucleus of eukaryotic cells. It separates the contents of the nucleus from the cytoplasm. The kärnmembran is composed of two lipid bilayers, an inner and an outer membrane, which are separated by a space called the perinuclear cisterna. Embedded within the kärnmembran are nuclear pores, which are protein-lined channels that regulate the passage of molecules between the nucleus and the cytoplasm. These pores are essential for the transport of RNA, proteins, and other molecules required for gene expression and cellular function. The outer nuclear membrane is continuous with the endoplasmic reticulum, and both membranes are supported by a network of intermediate filaments called the nuclear lamina. The kärnmembran plays a crucial role in maintaining the integrity of the genome and regulating nuclear transport, thereby influencing various cellular processes including DNA replication, transcription, and cell division. Its presence is a defining characteristic of eukaryotic cells.