Tuumamembraan

Tuumamembraan is a term used to denote the membrane surrounding the nucleus in eukaryotic cells, commonly referred to as the nuclear envelope. It consists of two lipid bilayers: an inner nuclear membrane and an outer nuclear membrane, separated by a fluid-filled perinuclear space. The outer membrane is continuous with the endoplasmic reticulum and can bear ribosomes on its cytoplasmic surface, whereas the inner membrane is supported by a protein mesh called the nuclear lamina.

The nuclear envelope contains numerous nuclear pore complexes that span both membranes, forming conduits for the selective exchange of proteins, RNAs, and other molecules between the nucleoplasm and the cytoplasm. Transport through these pores is tightly regulated by transport receptors and localization signals.

The inner membrane interfaces with chromatin via the nuclear lamina, which provides mechanical support and helps organize the genome within the nucleus. This organization influences processes such as DNA replication, transcription, and repair, and it can affect gene expression patterns.

During cell division in many species, the nuclear envelope disassembles to permit chromosome segregation and then reassembles around daughter genomes in telophase. The envelope’s integrity and composition are maintained by a range of lipids and proteins, including lamins, nucleoporins, and other scaffold and transport factors. Malfunctions in nuclear envelope components are associated with a variety of diseases, collectively referred to as laminopathies, which can affect muscle, adipose tissue, and neural systems, among others.

The term tuumamembraan is not universally used in English-language literature; the established term for this structure is the nuclear envelope or nuclear membrane.