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Lipid membranes biological roles

Phosphatidylinositol 4-phosphate (PI-4-P, 3) is the second most abundant inositol phospholipid in biological membranes. It is a product of phosphorylation by four different species of PI 4-kinases (21), and it is a precursor to PI-4,5-P2 and PI-3,4,5-P3. These kinases are the two inositol lipids whose biological roles are understood best. The biological function of PI-4-P is not well known however, the studies in yeast indicate its role extends beyond the substrate for PI 5-kinase (21), such as regulation of vesicular trafficking and protein secretion from Golgi. PI-4-P is removed by the subsequent phosphorylation to PI-4,5-P2 or dephosphorylation to PI by ER-localized phosphatase (21). [Pg.1482]

In addition to the passive diffusional processes over lipid membranes or between cells, substances can be transferred through the lipid phase of biological membranes through specialized systems, i.e., active transport and facilitated diffusion. Until recently, the active transport component has been discussed only for nutrients or endogenous substances (e.g., amino acids, sugars, bile acids, small peptides), and seemed not to play any major role in the absorption of pharmaceuticals. However, sufficient evidence has now been gathered to recognize the involvement of transporters in the disposition of pharmaceuticals in the body [50, 127]. [Pg.113]

In this concept we have described the successful interplay between organic synthesis, biophysics and cell biology in the study of protein lipidation and its role in the selective targeting of proteins like Ras to the plasma membrane. The development of new... [Pg.380]

Models for biological membranes have either been realized as planar lipid monolayers at the gas-water interface (3) or as bi-molecular lipid membranes (BLM) (4) and spherical liposomes (vesicles), respectively (5 6) (Figure 2.). All these models that are only composed of lipid molecules exhibit a diminished stability compared to natural cell membranes. Obviously the protein part besides being functionally important plays a role in terms of stability of biomembranes. This is the case not only for the integral but especially for the boundary proteins ( 7). [Pg.209]

While examples such as these provide evidence that strong interactions of negatively-charged membrane lipids with membrane proteins the role in maintaining asymmetric distributions of lipids aaoss biological membranes is unclear. In any event such effects are likely to be of minor importance relative to actively mediated phospholipid translocation processes. [Pg.46]

Fats are a remarkably effective form of energy storage. Several classes of complex lipids play important roles in human physiology and are key constituents of biological membranes. [Pg.253]

Although my central interest in these complex lipids is the role that they play in organizing the stracture of biological membranes, these complex phospholipids also... [Pg.256]

Competition between mono- and di-valent cations has an important role in biological processes. Furthermore, the lipophilicity of a ligand and its complex plays an important role in deciding whether a species is soluble in organic media of low polarity. This has important consequences in areas such as phase-transfer catalysis, the use of crown ethers as anion activators, and in cation transport through lipid membranes. Many crown ethers have now been synthesized with incorporation of long alkyl side chains and enhanced lipophilicity and used successfully in the above areas. [Pg.53]

The relative proportions of protein and lipid vary with the type of membrane (Table 11-1), reflecting the diversity of biological roles. For example, certain neurons have a myelin sheath, an extended plasma membrane that wraps around the cell many times and acts as a passive electrical insulator. The myelin sheath consists primarily of lipids, whereas the plasma membranes of bacteria and the membranes of mitochondria and... [Pg.370]

While there is no doubt that free lipids can facilitate the formation of hemozoin in model systems, their potential biological role must be placed in the appropriate context. The vast majority of these lipids are involved in cellular structures (organism membrane, organelles, etc.), not freely soluble in the cytoplasm. The methods of extraction modified from Bligh and Dyer [35] by Cohen [36] were designed to extract all of the available... [Pg.333]

Lipids are less well known to most people than are proteins or carbohydrates, yet they are just as essential to life. Lipids have many important biological roles, serving as sources of fuel storage, as protective coatings around many plants and insects, and as major components of the membranes that surround every living cell. [Pg.1051]

It is interesting that work on the internal motions of the molecules that produce lyotropic mesophases is more advanced. This is mainly because of the importance of the microscopic properties of these systems in solubilization and interfacial problems, problems which are encountered in industry as well as in cell membrane biology. The structural and functional roles of lipid molecules in biomembranes are much discussed investigations of the physicochemical properties of lipid media thus might provide orientations for biological studies. Moreover, the findings on the flexibility of the paraffinic chains in lyotropic mesophases might also be relevant to similar problems in thermotropic mesophases. [Pg.109]

Lipids play a number of important biological roles. Phospholipids are triesters of glycerol in which one ester is derived from a phosphatidylamine. They are important structural units in cell membranes. Prostaglandins are 20-carbon cyclopentane derivatives of arachidonic acid that have profound biological effects, even in minute quantities. Waxes are monoesters of long-chain acids and alcohols. [Pg.279]

Roles Fatty acids have four major biological roles 1. They are components of membranes (glycerophospholipids and sphingo- lipids) 2. Several proteins are covalently modified by fatty acids 3. They act as energy stores (triacylglycerols) and fuel molecules 4. Fatty acid derivatives serve as hormones and intracellular second messengers. [Pg.311]

Cullis, P. R. and de Kmijff, B. (1979). Lipid polymorphism and the functional roles of lipids in biological membranes. Biochim Biophys. Acta 559 399. [Pg.195]

The phospholipids are widely found in biological membranes and can be used as emulsifiers especially for intravenous fat emulsions, and as a key component of liposomes. The elucidation of factors governing the solubilization of drugs in phospholipid dispersions can provide some clues as to the biological role of interactions with lipid systems in vivo. " Phospholipids have been discussed above and in reference in the context of liposomes. [Pg.3594]

LIPIDS OF MEMBRANES CHEMISTRY, BIOLOGICAL ROLE AND APPLICATIONS AS DRUG CARRIERS... [Pg.173]


See other pages where Lipid membranes biological roles is mentioned: [Pg.2816]    [Pg.739]    [Pg.372]    [Pg.597]    [Pg.214]    [Pg.236]    [Pg.7]    [Pg.395]    [Pg.378]    [Pg.118]    [Pg.131]    [Pg.117]    [Pg.214]    [Pg.183]    [Pg.170]    [Pg.17]    [Pg.126]    [Pg.786]    [Pg.891]    [Pg.891]    [Pg.892]    [Pg.2235]    [Pg.492]    [Pg.91]    [Pg.3]    [Pg.173]    [Pg.198]    [Pg.665]    [Pg.329]    [Pg.41]   
See also in sourсe #XX -- [ Pg.173 ]

See also in sourсe #XX -- [ Pg.173 ]




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Biological membranes

Biological role

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