The volume of an erythrocyte after it is aded to a NaCl solu

Discussion in 'USMLE STEP 1' started by Guest, May 30, 2009.

  1. Guest

    Guest Guest

    the graph shows changes in the volume of an erythrocyte after it is aded to a NaCl solution. Which of the following is the most likely concentration( in mM) of NaCl? ( the graph shows basicaly a how erythrocyte double their volume).

    a. 75
    b. 150
    c. 300
    d. 500
    e. 1500
  2. Guest

    Guest Guest

    The ans is 75

    mM is different to mosm. 75 mM of NaCl would be equal to 150 Mosm sinc Na would contribute 75 and Cl 75. all other answers given will give a Mosm of 300 or more thus making the solution hypertonic so the Rbc should shrink not double the vol. 75mm of NaCl in this case would be equal to 150 Mosm which is hypotonic.

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