l T-Mobile 8:42 PM Conference 1 Homework Assignment Due: Friday, September 21, 2
ID: 146403 • Letter: L
Question
l T-Mobile 8:42 PM Conference 1 Homework Assignment Due: Friday, September 21, 2018 In frog sartorius muscle the following distribution of ions between cell interior and exterior is seen in an in vitro preparation at 25°C Cell interior [Nal 10.4 mM/Kg H2O [K1 124 [CII. 1.5 [HCOs1- 12 Ca2, Mg2 Phosphate, A, Cell exterior INa'l. 109 mM/Kg H:0 (.h" 2.3 etc. In addition, the cell membrane potential is measured by microelectrodes to be -99.0 mV Do the following (1) Calculate the electrochemical potential gradient for Nat, K, C, and HCO3, and describe the direction of each gradient. Show your calculations, including your calculation of RT/ZE, Be sure to use the ionic valence (z) in your calculations (2) Which ions "appear" to be in equilibrium? (3) If Na" were in equilibrium across the membrane, what would you expect the membrane potential to be? Answer the question for HCO3 Back to UB MobileExplanation / Answer
EK = RT/F log(Na out)/(Na in)
where R is universal gas constant which is 8.314 J/Kmol
T= absotute temperature(in Kelvin)
F=Faraday constant 96485 or 9.648 *104 coulomb/mol
Z is the valency which is +1 for Na and K, -1 for Cl, HCO3-
Ek for Na+ =2.3 RT/ZF log 109/10.4 = 2.3* 8.314*298/1*96485 log 109/10.4
= 0.059/Z log 10.480 = 0.059/1* 1.0203 = 0.060203
Ek for K+= 2.3 RT/ZF log 2.3/124= 0.059/1*log 0.0185
= 0.059*-1.731= - 0.102
negative value indicates that the net movement will be from inside to out of the cell.
Ek for Cl-=2.3 RT/ZF log 78/1.5
= 0.059 log 52 = 0.059 *1.71600= 0.1012
Ek for HCO3-= 2.3 RT/ZF log 27/12= 0.059* log 2.25
= 0.059/1* 0.3521= 5.9691
2) K+ and Cl- appears to be in equilibrium.
3) If Na+ will be in equilibrium then no movement occurs for Na+ Ions across the membrane. Since potential difference is required for the movement.
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