Cours 2 CP NCI 2012 - Département de biologie
Cours 2 CP NCI 2012 - Département de biologie
Cours 2 CP NCI 2012 - Département de biologie
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The plasma membrane separates two media of different ionic composition<br />
Intracellular and extracellular media are neutral ionic solutions: in each<br />
medium, the concentration of (+) ions = (-) ions.<br />
Extracellular:<br />
[Na + ]e + [K + ]e + 2[Ca 2+ ]e = 140 +3 + (2 x 1.5) = 146 mM and [Cl - ]e = 146 mM<br />
Intracellular:<br />
[Na + ] i + [K + ] i + 2[Ca 2+ ] i = 7 + 140 + 0.0002 = 147 mM but [Cl - ] i = 7 mM<br />
In the intracellular compartment, other anions than chlori<strong>de</strong> ions are present<br />
and compensate for the positive charges (HCO 3 - , PO4 2- , aminoacids, proteins,<br />
nucleic acids, etc …).
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