Beng Final 2007

Beng Final 2007 - 6a) Consider a red blood cell as a sphere...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
6a) Consider a red blood cell as a sphere with a radius of 7 μm. We have modified the cell membrane so that it is only permeable to sodium ions. If this cell is immersed in a 0.15M NaCL solution, a 10 mV potential is produced across the cell membrane (the inside of the cell is positive). If the cell is immersed in a 0.3M NaCL solution, what potential would be measured (magnitude and polarity)? V = -58log(C in /C out )mV (4pts) 10 = -58log{[Na] in /[0.15]} mV [Na] in = 0.101 M When the cell is in immersed into the 0.3M NaCl soln, the membrane potential becomes V = -58log{[0.101]/[0.3]} = 27.42 mV (positive inside) b) Charged ions have to move across the membrane to cause this change in potential. Using the definition of capacitance C=Q/V where C is the capacitance of the interface between the two concentrations in farad, Q is the amount of charge in coulombs required to charge up the interface to a voltage V, how many moles of sodium ion must move across the membrane to produce this new potential assuming the capacitance of the red blood cell membrane is 1 μF/cm 2 . F=96,500 Cs/mol. (4 pts) Q = CV = 10 -6 x 4 x 3.1416 x (7x10 -4 ) 2 x (27.42-10) x 10 -3 / 96500 = 1.11x10 -18 moles c) In the discussion of the electrical properties of the glass microelectrode we talked
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/13/2008 for the course BENG 186B taught by Professor Peterchen during the Winter '08 term at UCSD.

Page1 / 5

Beng Final 2007 - 6a) Consider a red blood cell as a sphere...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online