Cytoplasmatic membrane

Fig. 6.8 Electron photomicrograph of mouse kidney mitochondria. The structure of both the cytoplasmatic membrane (centre) and the mitochondrial membranes is visible on the ultrathin section. Magnification 70,000x. (By courtesy of J. Ludvik)... 

The basic characteristic of the membrane structure is its asymmetry, reflected not only in variously arranged proteins, but also in the fact that, for example, the outside of cytoplasmatic (cellular) membranes contains uncharged lecithin-type phospholipids, while the polar heads of strongly charged phospholipids are directed into the inside of the cell (into the cytosol). 

Clotrimazole fonnally also is an imidazole derivative because of the presence of an imidazole ring in its structure. It is believed that, like miconazole, econazole, and other pure representatives of the imidazole class, it also inhibits the biosynthesis of ergosterin in the cytoplasmatic membrane of fungi. 

The uptake of the chelated ferric ion through the cytoplasmic membrane depends on ATP-binding cassette (ABC) transporters. The energy for the transport is supplied by the TonB-ExbB-ExbD protein cluster, located on the cytoplasmatic membrane. 

Now, it has been observed that calcium ions are needed (11, 12, IS, 14) for the release of acetylcholine. If we assume the same trigger mechanism as was described previously, we see that the penetration of calcium gives rise to a much stronger water lattice and membrane structure breakdown than does that of sodium. The bilayer membrane of the vesicles, which is tightly coupled to the presynaptic membrane via the cytoplasmatic water, is affected equally strongly and the probability of... 

The Fenna-Matthews-Olson (FMO) protein is an unusual, water-soluble chlorophyll protein found only in green sulfur bacteria. [18] It is believed to be located between the chlorosome and the cytoplasmatic membrane and functions as an excitation transfer link between the chlorosome and the reaction center. Each subunit contains 7 BChl a molecules embedded in a primarily /3 sheet structured protein. The protein has a trimeric quaternary structure, with a three-fold axis of symmetry in the center of the complex. [55] The green nonsulfur bacteria do not contain the FMO protein. In these organisms the chlorosome transfers energy directly to the integral membrane core antenna B808-865, and then to the reaction center. 

In the case of hepatocytes the immobilization of galadose motifs on the surface enhances the spedfic interaction with cells owing to the specific binding between the galadose moiety and the asyaloglycoprotein receptor present on the cytoplasmatic membrane [25, 26]. 

Fig. 14.5. Electron micrograph of a section from a yeast cell. The outer envelope is the cell wall. The inner double line is the cytoplasmatic membrane. (Reprinted from J. Koryta, Ions, Electrodes and Membranes, Fig. 70. Copyright J. Wiley Sons, Ltd. 1991. Reproduced with permission of J. Wiley Sons, Ltd.)...

As a result of large-droplet steatosis, the hepatocytes become enlarged, the fine cytoplasmatic structures are destroyed and the nucleus is pushed towards the cellular membrane. The functions of the nucleus are impaired or even halted. This also results in a strong tendency of the fatty cells to develop necrosis even under mildly... 

The formation of crystalline microfibrils has been elucidated using the bacterium Acefol acter xylinum as cellulose producing model. It appears that individual cellulose chains are extruded at multiple cellulose-synthesizing sites located in the cytoplasmatic membrane of the organism. Cellulose synthesis produces 12 to 16 cellulose chains into the surrounding medium... 

Sufficient space for any cytoplasmatic protein subunits protruding out of the membrane can be accommodated... 

VMAT2 is a protein with 12 membrane segments, and both of its extremities are located in the cytoplasmatic site. The mechanism of VMAT2 action is complex and only partially... 

Morphologically, the fibres are composed of the cortex and the cuticle. Each of the two components is formed of various other morphological components (Table 9.6.3). The cortex contains cortical cells and the cell membrane complex. The cortical cell is further composed of macro-fibrils and intermacro-fibrillar material. The macro-fibrils consist of micro-fibrils and intermicro-fibrillar matrix. In summary, the cortex is formed of micro-fibrils (intermediate filament, IF, or keratin proteins, KP) and keratin associated proteins (IFAP or KAP), which compose the intermicrofibrillar matrix containing cytoplasmatic and nuclear remnants. This ensemble is wrapped up in the cuticle, as an external sheath which also has its own architecture, being formed of four layers the epicuticle, the a-layer, the exocuticle and the endocuticle. 

Despite the general toxic effect of solvents to whole cells, some microbial strains present an unusual tolerance to solvents (e.g.. Pseudomonas [69, 71], Rhodococcus [72]). This may involve an adaptation mechanism at the level of the cytoplasmatic membrane, aiming to restore its stability and fluidity, once dis-... 

The toxicity of organic solvents or hydrophobic substances for microorganisms depends mainly on their effects on biological membranes - similar to membrane effects of several anesthetics. This concerns especially effects on cytoplasmatic membranes. The following main changes of membrane structures and functions have been observed ... 

Accumulation of hydrophobic substances such as organic solvents in cytoplasmatic membranes. This accumulation causes structural and functional changes in the cytoplasmatic membranes and microbial cells. 

Structural changes in cytoplasmatic membranes, e.g., swelling of membrane bilayers, increase of surface and thickness of the membranes, changes in the composition of the membrane (e.g., changes in the fatty acid composition), modification of the microviscosity, damage of membrane structures (see below). 

Loss of membrane integrity, especially disruption of cytoplasmatic membranes, less damage of outer membranes. Because of these damages often complex cellular structures (e.g., vesicula) or cell functions (decrease of respiratory activities of mitochondria) are destroyed or inhibited. 

Interactions of the accumulated lipophilic substances with the cytoplasmatic membranes and especially hydrophobic parts of the cell or cell membranes. Lipid-lipid interactions and interactions between proteins and lipids of the membrane structure (lipid bilayers, membrane-embedded proteins) are discussed. 

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