Membrane transport through cell membranes

Transition metal bisadduct 138 Transition metal complexes 121,157,158 Transport through cell membranes 43,46 Triazolylboranes 8-9 Triple bonding, group 13 element compounds 75,76... 

Phosphatidylinositol. In biological membranes, phosphatidylinositol (PI) is activated by enzymatic digestion to give rise to cell signaling and transport through cell membrane. PI forms salts with divalent ions and creates a negative charge in liposomes. 

Anandamide (AEA) is the most studied member of a new class of lipid mediators, collectively called endocannabinoids. The biological activity of AEA at cannabinoid and noncannabinoid receptors depends on its Hfe span in the extracellular space, which is regulated by a rapid cellular uptake, followed by intracellular degradation by the enzyme AEA hydrolase (fatty acid amide hydrolase). Here, we present the methodological details of the procedures that we have developed to assay fatty acid amide hydrolase activity and to characterize AEA transport through cell membranes in a new ideal ex vivo system like brain synaptosomes. 

Evolutionary Aspects of Metal Ion Transport Through Cell Membranes John M. Wood... 

The molecular mechanism of amino acid transport through cell membranes is not clear it seems to require energy and may be hormonally controlled. To study amino acid transport in the intestines, investigators introduce the amino acid solution inside an intestinal loop and determine the rate of the appearance of the amino acid in the solution bathing the serosal surface. Some investigators study amino acid transport using everted intestinal loops with the serosa inside. 

A special type of driving force arises in Item 4 of Table 1.2. The process here is the selective transport of water through a semipermeable membrane from a dilute solution (high water concentration) to a more concentrated solution (low water concentration). The driving force is in this case the difference of the so-called osmotic pressure n, which makes its appearance in transport through cell membranes as well as in industrial processes termed reverse osmosis. We have occasion to take a closer look at osmotic-pressure-driven processes in Chapter 8. 

In the simplest transport mechanism called diffusion or passive transport, molecules can diffuse from a higher concentration to a lower concentration. For example, small molecules such as O2, CO2, urea, and water diffuse via passive transport through cell membranes. If their concentrations are greater outside the cell than inside, they diffuse into the cell. If their concentrations are higher within the cell, they diffuse out of the cell. 

MeOH is transported through the membrane by two modes diffusion and electro-osmotic drag. ° When MeOH comes into contact with the membrane, it diffuses through the membrane from anode to cathode and is also dragged along with the hydrated protons under the influence of current flowing across the cell. Therefore, a correlation between the MeOH diffusion coefficient and proton conductivity is observed. The diffusive mode of MeOH transport dominates when the cell is idle, whereas the electro-osmotic drag... 

Continuity of fhe wafer flux fhrough the membrane and across the external membrane interfaces determines gradients in water activity or concentration these depend on rates of water transport through the membrane by diffusion, hydraulic permeation, and electro-osmofic drag, as well as on the rates of interfacial kinetic processes (i.e., vaporization and condensafion). This applies to membrane operation in a working fuel cell as well as to ex situ membrane measuremenfs wifh controlled water fluxes fhat are conducted in order to study transport properties of membranes. 

The transport of K+ ions through cell membranes by antibiotics (valinomycin) has been a very important example. Addition of K+ ions to the subphase of a valinomycin monolayer showed that the surface potential became positive. This clearly indicates the ion-specific binding of K+ to valinomycin (Birdi, 1989). 

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