| membrane lipids | Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation. (12 Dec 1998) |
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| membrane of tympanum | <anatomy> The eardrum. (13 Nov 1997) |
| membrane potential | <physiology> More correctly, transmembrane potential difference: the electrical potential difference across a plasma membrane. See: resting potential, action potential. (18 Nov 1997) |
| membrane potentials | Ratio of inside versus outside concentration of potassium, sodium, chloride and other ions in diffusible tissues or cells. Also called transmembrane and resting potentials, they are measured by recording electrophysiologic responses in voltage-dependent ionic channels of (e.g.) nerve, muscle and blood cells as well as artificial membranes. (12 Dec 1998) |
| membrane protein | <protein> A protein with regions permanently attached to a membrane (peripheral membrane protein) or inserted into a membrane integral membrane protein). Insertion into a membrane implies hydrophobic domains in the protein. All transport proteins are integral membrane proteins. (18 Nov 1997) |
| membrane proteins | Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors. (12 Dec 1998) |
| membrane recycling | <cell biology> The process whereby membrane is internalised, fuses with an internal membranous compartment and is then re incorporated into the plasma membrane. In cells that are actively secreting by an exocrine method (in which secretory granules fuse with the plasma membrane), it is obviously essential to have some way of reducing the area of the plasma membrane. The membrane can then be used to form new secretory vesicles. The converse is true for phagocytic cells. (18 Nov 1997) |
| membrane transport | <cell biology> The transfer of a substance from one side of a plasma membrane to the other, in a specific direction and at a rate faster than diffusion alone. See: active transport. (18 Nov 1997) |
| membrane-type 3 matrix metalloproteinase | <enzyme> Sm3 is a soluble form of mt3-mmp, probably an alternatively sliced variant. Registry number: EC 3.4.24.- Synonym: mt3-mmp, sm3-mmp (26 Jun 1999) |
| membrane-type 4 matrix metalloproteinase | <enzyme> Cloned from breast carcinoma. Registry number: EC 3.4.24.- Synonym: mt4-mmp, mmp-17 gene product, mmp-17 (26 Jun 1999) |
| membrane-type matrix metalloproteinase | <enzyme> Activates gelatinase a; isolated from a human placenta cdna gene library; contains a transmembrane domain; do not use for any other numbered matrix metalloproteinases; genbank d26512 Registry number: EC 3.4.24.- Synonym: mt-mmp, mmp-x1 protein, matrix metalloproteinase, membrane-type, mmp14 gene product, mmp-14 gene product, mt1-mmp, matrix metalloproteinase 14, mt2-mmp, mmp15 gene product, mmp16 gene product (26 Jun 1999) |
| membrane vesicle | <cell biology> Closed unilamellar shells formed from membranes either in physiological transport processes or else when membranes are mechanically disrupted. They form spontaneously when membrane is broken because the free ends of a lipid bilayer are highly unstable. (18 Nov 1997) |
| membrane zippering | <cell biology> Process suggested to occur in phagocytosis in which the membrane of the phagocyte covers the particle by a progressive adhesive interaction. The evidence for such a mechanism comes from experiments in which capped B-cells are only partially internalised, whereas those with a uniform opsonising coat of antiIgG are fully engulfed. (18 Nov 1997) |
| peribacteroid membrane | <plant biology> Membrane derived from the plasma membrane of a plant cell and that surrounds the nitrogen fixing bacteroids in legume root nodules. Has a high lipid content and may regulate the passage of material from the plant cell cytoplasm to the symbiotic bacterial cell. The idea that it restricts leghaemoglobin to the peribacteroid space seems untenable since leghaemoglobin is found in the cytoplasm of some cells. (18 Nov 1997) |
| pericardiopleural membrane | A tissue fold jutting into the right or left embryonic pericardioperitoneal canal; it separates the developing pericardium from the pleural cavity and is formed by the growth of the common cardinal veins to the midline of the body. Synonym: pericardiopleural membrane, pleuropericardial membrane. (05 Mar 2000) |