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Homework Help: Is the concentration outside and inside the neuron important?

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

    During the action potential, Na+ ions move into the cell at a rate of about 2.98×10-7mol/m2/s. How much power must be produced by the active transport system to produce this flow against a +25.2 mV potential difference? Assume that the axon is 11.7cm long and 19.6um in diameter.

    Given Length, and Diameter. With this we can find resistance BUT we are not given rho so I'm not really sure what to do with the numbers. We are given the potential difference, and I converted mV to V. We are given a current of 2.98x10^-7 mol/m2/s.

    2. Relevant equations

    Is the concentration outside and inside the neuron important?
    Should a converstion be made from mol/m2/s to charge/s since current is C/s?

    3. The attempt at a solution

    I have tried three different ways of figuring out the power. First I tried to multiply the V by and I given but that didn't work. I tried to calculate R using the concentration inside and outside the cell (for rho) then using the diameter(turned radius) and the length to find R. Then used R to find power.

    I honestly have no idea where to go from here....
  2. jcsd
  3. Feb 23, 2008 #2
    Try and find the Force required to move the ions against the potential difference. Then relate it to work using the Work-Energy Theorem. Once you have the energy needed, you should be able to find out how much power is needed because you're given the rate at which the ions are moving in the transport system. Power is just the rate at which work is done.

    Good luck.
  4. Feb 24, 2008 #3
    So Im able to find the work using W=qV.....but in order to find power won't I need time? Since W/t=P, how would I find the time?
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