Membranene

Membranene are flexible, lipid-protein layers that enclose cells and their organelles. They create distinct compartments, regulate the movement of ions and molecules, and facilitate communication and signaling. The plasma membrane forms the boundary of the cell, while intracellular membranes define the compartments within the cytoplasm.

Most membranes consist of a phospholipid bilayer in which amphipathic lipids arrange with hydrophilic heads outward and hydrophobic tails inward. Cholesterol modulates fluidity and thickness; glycolipids contribute to cell recognition. Membranes host integral or peripheral proteins that serve as channels, transporters, receptors, enzymes, and anchors. The membrane is described by the fluid mosaic model, allowing lateral movement of lipids and proteins while maintaining selective permeability.

Various membranes perform diverse functions. Nuclear envelope encloses the genome; endoplasmic reticulum and Golgi apparatus synthesize and modify lipids and proteins; mitochondria and chloroplasts generate energy. Transport across membranes occurs by passive diffusion, facilitated diffusion via channels and carriers, and active transport powered by ATP or ion gradients. Vesicular trafficking moves cargo between organelles and to the plasma membrane. Membranes maintain electrochemical gradients that underpin signaling and energy conversion.

Membrane biology is central to health and disease; defects in transporters or fusion proteins cause disorders. In research, model systems such as liposomes and artificial bilayers are used to study permeability and protein function. Applications include drug delivery, biosensing, and the design of synthetic membranes in biotechnology.