Membranlag

Membranlag is a term used in several Scandinavian languages to denote a membrane layer—the lipid- and protein-containing boundary that encloses cells and organelles. In biology, membranlag refers to the phospholipid bilayer-based structures forming these boundaries and the molecules embedded in or associated with them. A typical membranlag consists of a phospholipid bilayer with integral and peripheral proteins, cholesterol, and various glycolipids and glycoproteins. The bilayer arranges with hydrophobic tails inward and hydrophilic heads outward, creating a hydrophobic core that acts as a selective barrier. The fluid mosaic model describes membranes as dynamic, with components that diffuse laterally and reorganize in response to cellular needs.

Membranal function includes maintaining ion and metabolite gradients through selective permeability, enabling signal transduction via membrane receptors, and supporting vesicular trafficking and organelle biogenesis. Membrans participate in energy generation, for example in the inner mitochondrial membrane, where electrochemical gradients drive ATP synthesis. Membranes are asymmetric in lipid and protein composition, and can form microdomains, such as lipid rafts, which organize signaling platforms.

Different membranes exist throughout the cell: the plasma membrane that encloses the cell, and internal membranes such as the endoplasmic reticulum, Golgi apparatus, mitochondria, and the nuclear envelope. Vesicles, lysosomes, and vacuoles are bounded by membranes as well.

In practice, membranlag is often translated as membrane layer, lipid bilayer, or cellular membrane in English. The term is primarily encountered in Scandinavian scientific literature rather than in standard English usage.