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Chemical and electrical gradient for ion X+

  1. Mar 3, 2012 #1
    Please check my answers. I tend to over-think and get simple questions wrong.

    A hypothetical cell membrane is positively charged on the intracellular side and negatively charged on the extracellular side. In this cell, the concentration of ion X+ in
    the intracellular space is high and in the extracellular space is low.

    http://s1140.photobucket.com/albums/n575/sanjanz2392/?action=view&current=f.jpg

    1) Does an electrical gradient exist for X+? If it exists, what direction is the electrical gradient?
    a) No.
    b) Yes, inward.
    c) Yes, outward.

    Yes, outward because opposite charges attract each other. I'm not completely sure because neither a membrane potential nor an equilibrium potential is given for the cell and ion.

    2) Does a concentration gradient exist for X+? If it exists, what direction is the concentration gradient?
    a) No.
    b) Yes, inward.
    c) Yes, outward.

    Yes, outward. high --> low

    3) Imagine an ion channel opens that allows X+ to flow. Will X+ flow across the membrane,
    through the ion channel? If so, what direction will the net electrochemical gradient(s) for X+ favor it flowing? (Assume the two gradients are of equal magnitude.)
    a) Yes, it will flow from extracellular to intracellular.
    b) Yes, it will flow from intracellular to extracellular.
    c) No, it will not flow.

    Yes, it will flow from intracellular to extracellular.


    4) What reasoning led you to your determination of which direction the ion would flow?
    a) Both the chemical and electrical gradients favor movement out.
    b) Both the chemical and electrical gradients favor movement in.
    c) The chemical and electrical gradients balance each other out.
    d) There are no gradients acting on X+.

    Both the chemical and electrical gradients favor movement out.

    5) Based on the concentration gradient, would you predict that the equilibrium potential for X+ is a positive or negative value? (Consider: you need an electrical force to counteract the chemical force.)
    a) positive membrane potential
    b) negative membrane potential

    positive membrane potential b/c electrical force is always equal and opposite of chemical force. chemical force is in, so electrical is out meaning X+ favors a more positive membrane potential at equilibrium


    PLEASE help. I'm really frustrated with this class.
     
  2. jcsd
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