Phospholipids adaptation lipids membranes

Fig. 7.1 Unsaturated fatty acids introduce kinks into phospholipids that are one mechanism by which cell membranes can adapt to low temperatures and high pressures by increasing membrane fluidity, (a) Depiction of the structure of a phospholipid containing saturated lipids, (b) Introduction of a single double bond creates a kink in the lipids, (c) Overall effect on the membrane structure of (a) and (b). Unsaturated phospholipids make the membrane less well-stacked (more fluid)...

Changes in the composition of the cytoplasmatic membrane. The compounds of the membranes such as lipids or proteins can influence the membrane characteristics and, therefore, the adaption to solvents. Mainly phospholipids in the membrane bilayer determine the partitioning of solutes and especially the resistance to... 

A molecular variation of plasma membrane has been reported by Puccia et al. Reduction of total lipids (XL) content and significant variations of triglyceride (TG) and phospholipids (PL) fractions were observed as a consequence of exposure of C. intestinalis ovaries to TBTCl solutions. In particular, an evident TG decrease and a PL increase were observed, which probably provoked an increment in membrane fluidity, because of the high concentration of long chain fatty acids and, as a consequence, PL. This could be a cell-adaptive standing mechanism toward the pollutants, as observed in Saccharomyces cerevisiae. Also the increase in the content of the polyunsaturated fatty acids (PUPA), important in the synthesis of compounds such as prostaglandin which are present in the ovary in a stress situation, was probably a consequence of a defense mechanism to the stress provoked by the presence of TBTCl. 

Cholesterol, another structural lipid capable of influencing membrane hardness , also plays an active role in temperature adaptations (Kreps, 1981 Chebotareva, 1983 Chebotareva and Dityalev, 1988 Sautin, 1989). Interposed between phospholipid molecules, it regulates the vital capacity of the membrane. 

Wodtke, E. (1978). Lipid adaptation in liver mitochondrial membranes of carp acclimated to different environmental temperatures. Phospholipid composition, fatty acid pattern and cholesterol content. Biochimica etBiophysicaActa 529,280-291. 

Figure 7.20. Effects of temperature on phase and static order of the membrane bilayer. Reductions in temperature from the physiological temperature of the organism (cell), that is, temperatures near those of adaptation or acclimation, lead to formation of gel-phase regions, which may separate from lipids that remain in the liquid-crystalline phase, the phase characteristic of most of the bilayer at physiological temperatures. At sufficiently low temperatures, the bulk of the membrane phospholipids enter the gel phase.

Fig. 1. The lipid-globular protein fluid mosaic model of membrane structure. The solid bodies represent globular proteins, some of which span the phospholipid bilayer represented by the open circles. Adapted from Singer and Nicholson (1972).

The purple membrane fragments that contained dark-adapted bacteriorhodopsin were used to form reconstituted vesicles with a mixture of phospholipids that contained 80% egg phosphatidyl choline and 20% bovine phosphatidylserine (Lipid Products, Nuttfield, England). The lipids in chloroform and methanol solutions were mixed to the desired composition, dried in a stream of nitrogen, placed in a 0.1-torr... 

Exceptions to cold temperature adaptation being accompanied by shorter chain or more unsaturated fatty acids Include mycelial phospholipids with greater unsaturation when grown at 36 C vs 20 C (77), and the lack of correlation of cold temperature acclimation with Increased lipid unsaturation or membrane fluidity by four fungi representative of four different fungal classes (78). 

Table 11-3 Phospholipid composition in Mol% total lipids of some liver cell membranes (adapted from [2] with permission of the Macmillan Press Ltd., London).

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