Ca2+ ion concentration

This reaction removes the Ca2+ ions that were present initially and those that were added as lime overall, the Ca2+ ion concentration is reduced. 

When the action potential reaches the synaptic bouton, depolarisation triggers the opening of voltage-operated calcium channels in the membrane (Figure 2.5). The concentration gradient for Ca2+ favours the passive movement of this ion into the neuron. The subsequent rise in cytoplasmic Ca2+ ion concentration stimulates the release of neurotransmitter into the synaptic cleft, which diffuses across this narrow gap and binds to receptors located on the postsynaptic neuronal membrane (Figure 2.5). 

Again, separating the ratio of Ca2+ ion concentration into two log terms we have ... 

Therefore, we can conclude that the interfacial equilibria and the complex equilibria are connected by cations, here by Ca2+ and H+ ions. Both equilibria are characterized by the same Ca2+ and H+ concentrations. In Figure 2.11, we can see that the interfacial equilibrium can be described solely by the Ca2+ ion concentration. Complex formation influences the interfacial equilibrium only via the decrease of the Ca2+ ion concentration. The concentration of the Ca2+ ion can be calculated from Equations 2.38 and 2.45, or 2.42 and 2.35, respectively. From these equations we obtain... 

The plasma membrane Na+/Ca2+ exchanger is a high-capacity and low affinity ionic transporter that exchanges three Na+ ions for one Ca2+ ion. When intracellular Ca2+ concentrations [Ca2+]i rise and the... 

Concentration values from any point along the line forming the lower portion of the boundary will yield an approximation to the solubility product, according to the expression Kv = [Ca2+][LAS-]2. The LAS concentration point at which this line abruptly changes direction gives an approximate value of the CMC of LAS in the presence of Ca2+ ions. 

As the concentration of C032 ions rises, Ca2+ ions precipitate in the reaction... 

Precipitation usually occurs when the concentration of a compound in solution exceeds the equilibrium solubility, although slow reaction kinetics may result in supersaturated solutions. For organic wastes in the deep-well environment, precipitation is not generally a significant partitioning process in certain circumstances, however, it may need to be considered. For example, pentach-lorophenol precipitates out of solution when the solution has a pH of <5,35,36 and polychlorophenols form insoluble precipitates in water high in Mg2+ and Ca2+ ions.37 Also, organic anions react with such elements as Ca2+, Fe2+, and Al3+ to form slowly soluble to nearly insoluble compounds. 

Characteristic properties of endopectate lyases are the high pH optimum, and a requirement for Ca2+ ions in order to maintain catalytic activity. The pH optimum of various endopectate lyases ranges from 8.0 to 9.5 (Refs. 4, 178, 234, 236, 243). Besides activation by Ca2+ ions, the optimal concentration of which is 1 mM,234,236,244 strontium salts were also considered in the case of Bacillus sp. lyase.234 The enzyme from Pseudomonas sp. was also partly activated by magnesium chloride,178 and for the lyase of Clostridium felsineum, salts of other bivalent cations had an activating effect as well.245 (Ethylenedinitrilo)tetraacetic acid completely inactivated all of the lyases mentioned. The activity of endopectate lyase from Pseudomonas was also lessened in the presence of sodium chloride, potassium chloride, and dipotassium hydrogen phosphate (K2HP04). 

ATP-dependent Ca2+ pumps and Na+,Ca2+ antiporters act in concert to maintain a low concentration of free cytosolic Ca2+. The concentration of cytosolic free calcium ion, [Ca2+] , in unstimulated cells is between 10 8 and 1 O 7 mol/1, which is more than 10,000-fold lower than extracellular free Ca2+. Most intracellular Ca2+ is stored in... 

FIGURE 32-2 Changes in extracellular ion concentrations following ischemia. Extracellular pH starts to decrease immediately after the onset of ischemia. This change is accompanied by slight increases in the extracellular concentrations of K+, Ch and Na+. After about 1 min of ischemia, a dramatic shift of ions occurs, with K+ leaving cells and Ca2+, CT and Na+ leaving the extracellular space (from [1] with permission). 

Jizomoto and Hirano [3.41 ] tried to increase the amount of drug inclusions in liposomes by inserting Ca2+ ions in dipalmitoylphosphatidylcholine (DPPC) liposomes. The included volume (mL) per g of liposomes is called Vcap, and this can be increased as a function of the Ca2+ concentration up to ten fold of the minimum Vcap The increase in Vcap is attributed to the electrostatic repulsion between the Ca ions, which reduces the number of lamella and increases the diameter of the liposomes to a certain extent, but increases substantially. A calculated simulation of this thesis is in reasonable agreement with the measurements... 

Blaustein It depends on the region. If you are talking about the space between the plasma membrane and the SR, that volume is very small. There will only be a few Ca2+ ions in such a space, even if it is a couple of hundred nanometres wide. This is with a free Ca2+ concentration of 100 nM. 

Ca2+ homeostasis that results from graded Ca2+ influx through voltage-dependent Ca2+ channels (Fleischmann et al 1994) and spontaneous intracellular Ca2+ release through ryanodine receptors. Thus the myocyte integrates numerous Ca2+ inputs and the concentration of cytosolic free Ca2+ ([Ca2+]j) at any given time is the net result of the activity of these Ca2+ channels, as well as that of Ca2+ pumps and exchangers that remove Ca2+ ions from the cytosol. 

Typical exchange isotherms for the reactions Ca2+ + 2 Na+ R Ca2+ R + 2 Na+. In dilute solutions the exchanger shows a strong preference for Ca2+ over Na+. This selectivity decreases with increasing ion concentration. The 45° line represents the isotherm with no selectivity. 

Hard water is the name given to water supplies that contain significant concentrations of Mg2+ and Ca2+ ions. Check on the solubility of ionic compounds formed with these ions and predict what problems they may cause. 

As is often the case, tissue-specific control mechanisms operate to optimise adaptation to particular conditions. For example, muscle contraction requires an increase in cytosolic calcium ion concentration (see Section 7.2.1, Figure 7.4). During exercise when energy generation needs to be increased, or from a more accurate metabolic point of view, when the ATP-to-ADP ratio falls rapidly, and the accompanying rise in [Ca2 + ] activate (i) glycogen phosphorylase which initates catabolism of... 

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