1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric field of a cell membrane

  1. Jan 23, 2008 #1
    1. The problem statement, all variables and given/known data

    he fluid within a living cell is rich in potassium chloride, while the fluid outside it predominantly contains sodium chloride. The membrane of a resting cell is far more permeable to ions of potassium than sodium, and so there is a transport out of positive ions, leaving the cell interior negative. The result is a voltage of about -63.0mV across the membrane, called the resting potential. If the membrane is 7.85nm thick, and assuming the electric field E across it is constant, determine the magnitude of E.

    Assume that the membrane's cytoplasmic (interior of cell) charge can be attributed to the presence of a certain fraction of negatively charged phospholipid molecules, each with a cross-sectional area of 0.550e-9m2. If each negatively charged lipid carries -1.60e-19C, how many such molecules are found in 1.0e-6m^2 of the inner surface of the membrane? What percentage of the membrane's inner surface do these molecules cover?

    Q=CV
    E=sigma/e0
    sigma=Q/a

    ok, I got E which is 8.03e6 N/C that's easy... but how do i start from here? I am so lost... I tried using Q=CV, and i got 1410 as the answer for how many of those molecules are in 1e-6 m^2 of membrane, but isn't the % 77.6%? I keep getting it wrong...
     
  2. jcsd
  3. Jan 27, 2009 #2
    How did you get the answer for the molecules??
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Electric field of a cell membrane
  1. Cell Membrane Question (Replies: 0)

Loading...