The extracellular and intracellular concentrations of Na+ and K- in dog skeletal

Question

The extracellular and intracellular concentrations of Na+ and K- in dog skeletal muscle are as follows: [Na+]OUT = 150 mM, [Na+]IN = 12 mM, [K-]OUT = 2.7 mM, [K-]IN = 140 mM.

a)Calculate ?G for the transport of 3Na+ out of the cell and 2K- into the cell, assuming a temperature of 37°C and a membrane potential of –60 mV.


b) If the intracellular [Pi] = 5 mM, what intracellular [ATP]/[ADP] ratio is required to maintain the Na+/K-pump operational? (?Go’for the hydrolysis of ATP is –30.5 kJ mol–1.)

Explanation / Answer

(a) ?G = qE = (3 * 1.60e-19 C / ion)(6.022e23 electrons/mol) (0V - (-60e-3 V)) + (2 * 1.60e-19 C / ion)(6.022e23 electrons/mol) ((-60e-3 V) - 0 V) = (3 - 2) F V = 5.78e3 J/mol (b) ATP --> ADP + Pi + Na/K translocation, ?Go = -30.5 kJ/mol + 5.78 kJ/mol Keq = exp( -?G / RT) = exp( - (-30.5e3 J/mol + 5.78e3 J/mol) / [(8.314 J/K*mol)(37+273 K)] ) = 1.46e5 = [ADP] [Pi] / [ATP] [ATP] / [ADP] = [Pi] / Keq = (5e-3 M) / 1.46e5 = 3.4e-7

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.