Suppose an axon cell membrane is experiencing the end of a stimulus event and th

Question

Suppose an axon cell membrane is experiencing the end of a stimulus event and the voltage across the cell membrane is instantaneous at 30 mV. Assume the membrane is 10 nm thick. At this point the Na/K-ATPase molecular pump starts to move the excess Na+ ions back to the exterior. (a) How much work does it take for the pump to move the first sodium ion? (b) Estimate the electric field (including direction) in the membrane. (c) Estimate the force on that first sodium ion. (d) What is the electric field (including direction) under normal resting conditions when the voltage across the membrane is -70 mV

Explanation / Answer

(a) work done = qV = 1.602 x 10-19 x 30 x 10-3 = 4.806 x 10-15 J = 0.03 eV

(b) electric field = V / thickness = 30 x 10-3/ 10 x 10-9 = 3x 106 N/C

(c) force on sodium ion = charge of sodium ion x electric field = 1.602 x 10-19 x 3 x106 = 4.806 x 10-13 N

(d) electric field = 70 x 10-3/ 10 x 10-9 = 7 x106 N/C

here electric field is directed into the membrane

PLEASE RATE

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