Membrane structure and function

Tyler DD, Sutton CM Respiratory enzyme systems in mitochondrial membranes. In Membrane Structure and Function, vol 5. Bittar EE (editor). Wiley, 1984. 

While the fluid mosaic model of membrane stmcture has stood up well to detailed scrutiny, additional features of membrane structure and function are constantly emerging. Two structures of particular current interest, located in surface membranes, are tipid rafts and caveolae. The former are dynamic areas of the exo-plasmic leaflet of the lipid bilayer enriched in cholesterol and sphingolipids they are involved in signal transduction and possibly other processes. Caveolae may derive from lipid rafts. Many if not all of them contain the protein caveolin-1, which may be involved in their formation from rafts. Caveolae are observable by electron microscopy as flask-shaped indentations of the cell membrane. Proteins detected in caveolae include various components of the signal-transduction system (eg, the insutin receptor and some G proteins), the folate receptor, and endothetial nitric oxide synthase (eNOS). Caveolae and lipid rafts are active areas of research, and ideas concerning them and their possible roles in various diseases are rapidly evolving. 

Section V deals with aspects of extracellular and intracellular communication. Topics covered include membrane structure and function, the molecular bases of the actions of hormones, and the key field of signal transduction. 

Phytosterols have been demonstrated as being anti-cancer components in the diet (Awad and Fink 2000). Scientific studies indicate that phytosterols may offer profection against colon, breast and prostate cancers (Vanderhaeghe and Bouic, 2000). The possible mechanisms, as reported by these authors, include the effect of phytosterols on membrane structure and function and on the signal transduction pathways that regulate tumor growth and apoptosis. The rice bran derived phytosterol-cycloartenol-ferulic acid ester on the central nervous system has been studied by Hiraga et al. (1993). 

H. R. Petty, Molecular Biology of Membranes. Structure and Function, Plenum Press, New York, 1993. 

Electrolytes are involved in many metabolic and homeostatic functions, including enzymatic and biochemical reactions, maintenance of cell membrane structure and function, neurotransmission, hormone function, muscle contraction, cardiovascular function, bone composition, and fluid homeostasis. The causes of electrolyte abnormalities in patients receiving PN may be multifactorial, including altered absorption and distribution excessive or inadequate intake altered hormonal, neurologic, and homeostatic mechanisms altered excretion via gastrointestinal and renal losses changes in fluid status and fluid shifts and medications. 

NEUROCELLULAR ANATOMY 3 CELL MEMBRANE STRUCTURES AND FUNCTIONS 21... 

Evans WH, Graham JM. Membrane Structure and Function, IRL Press, Oxford, UK, 1989. 

The mercuric ion, Hg2 +, which is obtained after oxidation in the red blood cells and other tissues, is able to form many stable complexes with biologically important molecules or moieties such as sulphydryl groups. The affinity of mercury for sulphydryl groups is a major factor in the understanding of the biochemical properties of mercuric compounds, resulting in interference with membrane structure and function and with enzyme activity. 

UV-induced ROS are extremely toxic to cells by causing oxidative damage to all biomolecules (Sies 1991). For instance, lipids, which are major compounds of all biological membranes, may be destroyed by ROS. After a first initiation reaction an unsaturated fatty acid is converted to a peroxyl radical, which in turn attacks another unsaturated fatty acid finally leading to free radical cascades. This photochemical peroxidation of unsaturated fatty acids may be particularly damaging for membrane structure and function (Bischof et al 2006a). 

Trichothecene mycotoxin Toxin produced by fungal molds it inhibits protein synthesis, impairs DNA synthesis, and interferes with cell membrane structure and function. 

Trichothecene mycotoxins are produced by a number of fungal molds of the Fusarium, Myrotecium, Trichoderma, and Stachybotrys genera. They inhibit protein synthesis, impair DNA synthesis, and interfere with cell membrane structures and functions. The potential routes of exposure are inhalation, ingestion, and skin absorption. A terrorist may take advantage of any of these routes. 

The mechanism of DEA toxicity is unknown but may be related to its high tissue accumulation and effects on phospholipid metabolism, resulting in alterations in membrane structure and function. ... 

One approach to understanding membrane function is to study membrane composition—to determine, for example, which components are common to all membranes and which are unique to membranes with specific functions. So before describing membrane structure and function we consider the molecular components of membranes proteins and polar lipids, which account for almost all the mass of biological membranes, and carbohydrates, present as part of glycoproteins and glycolipids. 

The following experimental observations are related to biological membrane structure and function. Discuss the implications of each observation with respect to membrane structure. 

Gullikson, G.W., et al. 1977. Effects of anionic surfactants on hamster small intestinal membrane structure and function Relationship to surface activity. Gastroenterology 73 501. 

Thornborough, J. R., ed. (1994, November). Membrane Function Membrane Structure and Function, Membrane Transport of Nonelectrolytes, Membrane Transport of Electrolytes, McGraw-Hill, New York. 

L.M. (Eds.), Drug and Anesthetic Effects on Membrane Structure and Function, Wiley-liss, NewYork 1991. 

Trudell J.R., in Drug and Anesthetic Effects on Membrane Structure and Function, R.C. Aloia, C.C. Curtain, L.M. Gordon (Eds.), Wiley-Iiss, New York 1991, pp. 1 13. 

---