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The sodium–potassium pump (sodium–potassium adenosine triphosphatase, also known as Na + /K +-ATPase, Na + /K + pump, or sodium–potassium ATPase) is an enzyme (an electrogenic transmembrane ATPase) found in the membrane of all animal cells. It performs several functions in cell physiology. The Na + /K +-ATPase enzyme is active (i.e. it ...
Potassium is the major cation (K +, a positive ion) inside animal cells, while sodium (Na +) is the major cation outside animal cells.The difference between the concentrations of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential.
Voltage-gated ion-channels are usually ion-specific, and channels specific to sodium (Na +), potassium (K +), calcium (Ca 2+), and chloride (Cl −) ions have been identified. [1] The opening and closing of the channels are triggered by changing ion concentration, and hence charge gradient, between the sides of the cell membrane. [2]
Thus the membrane potential will not be right at E K, but rather depolarized from E K by an amount of approximately 5% of the 140 mV difference between E K and E Na. Thus, the cell's resting potential will be about −73 mV. In a more formal notation, the membrane potential is the weighted average of each contributing ion's equilibrium ...
[10]: 322 Ternary alkali metal halide oxides, such as Na 3 ClO, K 3 BrO (yellow), Na 4 Br 2 O, Na 4 I 2 O, and K 4 Br 2 O, are also known. [10]: 83 The polyhalides are rather unstable, although those of rubidium and caesium are greatly stabilised by the feeble polarising power of these extremely large cations. [10]: 835
Na + channels open at the beginning of the action potential, and Na + moves into the axon, causing depolarization. Repolarization occurs when K + channels open and K + moves out of the axon, creating a change in electric polarity between the outside
Potassium channels function to conduct potassium ions down their electrochemical gradient, doing so both rapidly (up to the diffusion rate of K + ions in bulk water) and selectively (excluding, most notably, sodium despite the sub-angstrom difference in ionic radius). [4] Biologically, these channels act to set or reset the resting potential in ...
ν i is the number of ions i in the formula unit of the electrolyte (e.g. 2 and 1 for Na + and SO 2− 4 in Na 2 SO 4). Kohlrausch's evidence for this law was that the limiting molar conductivities of two electrolytes with two different cations and a common anion differ by an amount which is independent of the nature of the anion.