Originally Posted by Bonsay
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?
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