Membranei

Membranei is a term encountered in some Latin- and historical-style scientific writings to refer to membranes or membranous structures. In contemporary biology, the standard plural is membranes, and membranei is rarely used outside of stylistic or archaic contexts. When it appears, membranei typically signals a collection of membranes or membranous boundaries within a system.

Biological membranes are thin, flexible barriers that enclose cells and organelles, define compartments, and regulate exchange with the environment. They are primarily composed of a phospholipid bilayer with embedded proteins, which together form a semi-permeable barrier. The lipid components confer fluidity and insulation, while proteins mediate transport, signaling, enzymatic activity, and cell recognition. Cholesterol and other lipids modulate membrane fluidity and stability, influencing function under different temperatures and conditions.

Membranes perform several core roles: protecting cellular and subcellular interiors, controlling the passage of ions and molecules, facilitating energy production and signaling, and maintaining distinct chemical environments. They also participate in processes such as endocytosis, exocytosis, and membrane trafficking.

Common examples of membranous structures include the cell’s plasma membrane; the outer and inner membranes of mitochondria; the nuclear envelope; and extracellular membranes such as basement membranes and serous membranes (peritoneum, pleura, pericardium). Histology and physiology distinguish mucous, serous, synovial, and cutaneous membranes by location and function.

In research and industry, synthetic and model membranes—lipid bilayers, polymeric films, and hybrid systems—are used to study transport, signaling, and filtration. Membranei, when used, generally refer to membranes as a plural concept rather than a specific structure. See also membranes, membrane proteins, and lipid bilayers.