Potassium electrochemical potential

Action on the plasma membrane is the first and most fundamental of the bewildering array of deleterious effects of the cinnamic and benzoic acids. They reduce the transmembrane electrochemical potential with the immediacy and extent of that action depending on the concentration and lipid solubility of the compound.35,37,45,60 Rate of uptake also is concentration and pH-dependent, with transfer into and across the membrane greatest with lower pH conditions and higher external concentrations.60 Phenolic acid-induced depolarization of membranes causes a nonspecific efflux of both anions and cations accompanying the increased cell membrane permeability, and these membrane effects correlate with an inhibition of ion uptake. The phenolic acids suppress absorption of phosphate, potassium, nitrate, and magnesium ions, and overall changes in tissue... 

The coupling between chemical reactions and transport in biological membranes, such as the sodium and potassium pumps, is known as active transport, in which the metabolic reactions cause the transport of substances against the direction imposed by their thermodynamic force of mainly electrochemical potential gradients. 

Potassium leaves the cell, while the net flow of sodium is inward. A nonequilibrium stationary state for the cell at rest is maintained by the sodium and potassium pumps, which pump out the entering sodium ions and pump the leaking potassium ions back into the cell interior, using a certain metabolic output. The sodium transfer is coupled with the chemical reaction. The electrochemical potential difference for sodium ions is expressed as... 

To construct the potential pH diagrams of the different elements, all their possible redox processes with water, oxygen, and hydrogen have to be taken into account, and the electrochemical potentials have to be calculated. In addition, the dissolution/precipitation equilibria (e.g., hydrolysis) have to be taken into consideration, as well. The main dissolved ions in groundwater (calcium, magnesium, sodium, and potassium cations hydrocarbonate/carbonate, chloride,... 

Pumps are proteins that can transport ions against electrochemical potential gradients using adenosine-5-triphosphate (ATP) as an energy source. Sodium-potassium pumps maintain intracellular sodium and potassium concentrations in animal cells and also control salt and water absorption by the epithelial cells in the intestine and kidney. The sodium-potassium pump transports three sodium ions out of the cell and two potassium ions into the cell at the cost of one molecule of ATP. The 3 2 coupling ratio results in net loss of sodium ions into the cell down an electrochemical gradient and maintains cell volume. Currently, considerable research is attempting to elucidate the structures of the various isoforms and subunits of sodium potassium pumps. 

The cardiac action potential can be divided into five phases, numbered 0-4. These phases result from the subsequent or parallel activity of ion channels (Figure 3.2) and/or transporters. Initially, the cell is polarized to near the electrochemical potential for potassium ions because of high K+ conductance at rest. A rapid depolarization is initiated by the activation of the fast inward Na+ current (phase 0). This depolarization is followed by a brief partial repolarization mainly resulting from the activation of the transient outward current (/t0) and the inactivation... 

One basic oscillatory system uses the kinetic behavior of protein channels for sodium and potassium ion in a nerve membrane. Before elecflical excitation, the sodium channels are closed to sodium ion flow and the electrochemical gradient of 110 mV possible with the sodium ion gradient does not develop. The more permeable potassium channels tap the potassium ion gradient to produce an internal electrical potential of —60 mV relative to the external solution as ground. On excitation, the transient channels open and then close. As the sodium channels open, the sodium electrochemical potential of 110 mV appears to produce a peak internal potential of -60-1-110 = + 40 mV, The one-shot oscillation is completed as the sodium channel closes, the sodium-ion induced potential is lost, and the internal potential returns to the potassium channel dominated potential of -60 mV. The entire oscillation is controlled only by the sodium and potassium channels and the sodium and potassium ion concentration gradients across the membrane. 

It is well known that the resting and dynamic electrical activity of the brain is a consequence of electrochemical potentials across membranes. Many other aspects of electrochemistry are also familiar in the neurosciences. Hence it may seem paradoxical to have suggested that the electro-analytical techniques are far afield of the mainstream of neurobiology. However, neuronal membrane potentials depend on ionic charge distributions and fluxes insofar as is known, electron current plays no role. Just the opposite is true for electroanalytical techniques—ionic conductance is of minimal importance but electron flow (current) is the essence of the measurement. The electrodes employed do not sense membrane potentials or respond to sodium or potassium fluxes rather, they pass small but finite currents because molecules close to their surface undergo oxidation or reduction. Such electrochemical measurements are called faradaic (because the amount of material converted at the electrode surface can be calculated from Faraday s law). 

The antibacterial effect of metal ions and especially silver, copper and zinc ions is well known. Silver and silver ions are used in medicinal treatments ranging from severe burns to Legionnaires Diseases. Silver-based products are also applied in water purification processes. Metal ions achieve their antibacterial effect by two mechanisms First the metal ions influence the electrochemical potential between the internal and external parts of the cell, and second, after penetration of ions into the cell, they compete with other essential ions like magnesium, calcium and potassium and they aggregate with thiol groups of enzymes and proteins. 

ELECTROCHEMICAL POTENTIALS OF POTASSIUM AND CHLORIDE IN THE PROXIMAL RENAL TUBULES OF NECTURUS MACULOSUS... 

Voltage-gated potassium (Kv) channels are membrane-inserted protein complexes, which form potassium-selective pores that are gated by changes in the potential across the membrane. The potassium current flow through the open channel follows by the electrochemical gradient as defined by the Nernst equation. In general, Kv channels are localized in the plasma membrane. 

Fig. 9. Capacitance-potential curves for a number of common electrochemical solvents containing O lM potassium hexafluorophosphate, a relatively non-adsorbing electrolyte. (From Payne 1967, 1970.)...

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