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    1. #1
      Member Bonsay's Avatar
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      Paramecium-electrotaxis

      Ok, this is a kind of "homework" question.
      We have a paramecium and two electrodes in the water. The paramecium migrates to the cathode.

      ---------------------> (-)

      Then we switch the electrodes. The paramecium starts going for the cathode again, but this time he dies quickly and stops moving.

      <-- (+)

      Anyone have an idea why? My hypothesis was that a current is created where the positive particles go to the negative pole, taking the paramecium with it or that it's the charge of the cell itself. But then it wouldn't make sense why it stops moving altogether when switching the electrodes.

      Perhaps it has something to do with the electrolysis of water. H2-cathode, 02-anode.

      I know it's not an everyday homework question and would probably need some actual research, but just in case somebody knows this.
      Last edited by Bonsay; 04-19-2009 at 11:49 AM.
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    2. #2
      Dismember SnakeCharmer's Avatar
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      Quote Originally Posted by Bonsay View Post
      Anyone have an idea why? My hypothesis was that a current is created where the positive particles go to the negative pole, taking the paramecium with it or that it's the charge of the cell itself. But then it wouldn't make sense why it stops moving altogether when switching the electrodes.

      Perhaps it has something to do with the electrolysis of water. H2-cathode, 02-anode.
      You're missing something important in the bolded part.

      Electrotaxis is movement in response to electric stimuli. That means the cell is not 'carried' by the current, the cell moves by itself towards the electrode.
      That's why it stops when it dies- dead cells don't respond to stimuli and don't move by themselves.
      I think you need to explain why it died, not why it stopped moving.

      And no, I have no idea why it would die, but try looking for something that has to do with the membrane potential (voltage difference between cell interior and exterior). The cell needs that potential to survive and it needs it to sense changes the electric field.

      If you do find an answer, please post it here. It's an interesting question.

      EDIT:
      found this:
      "Hyperpolarization of the membrane potential causes an increase in the beating frequency of cilia and depolarization causes ciliary reversal." So, Paramecium needs to depolarize in order to change direction, but I don't know how this would kill it. Maybe because it can not repolarize in pure water?
      Last edited by SnakeCharmer; 04-19-2009 at 12:57 PM.

    3. #3
      Member Bonsay's Avatar
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      Yeah, I knew that it's active movement, so I just added a "but" under the part you quoted, since I didn't have much time to expand on my thoughts.
      I'll keep trying to find out things about it, but don't know if I'm going to get anywhere soon.
      Thanks for responding though. And thanks for the extra info.
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