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THE VARIATION OF ELECTRICAL RESISTANCE WITH APPLIED POTENTIAL : III. IMPALED VALONIA VENTRICOSA
1Laboratories of The Rockefeller Institute for Medical Research.
The Journal of General Physiology
|October 30, 2009
Summary
Electrical resistance and polarization in Valonia ventricosa cells were studied across five stages. Back electromotive force (EMF) from polarization significantly influences apparent protoplasm resistance, with capacitance around 1 microfarad/cm².
Area of Science:
- Cellular electrophysiology
- Membrane biophysics
- Plant cell physiology
Background:
- The electrical properties of cell membranes are crucial for cellular function.
- Valonia ventricosa, a large marine alga, provides a model system for studying protoplasm electrical characteristics.
Purpose of the Study:
- To measure electrical resistance and polarization in Valonia ventricosa protoplasm.
- To correlate these electrical properties with different stages of the cell's natural potential difference (P.D.).
- To investigate the role of back electromotive force (EMF) in apparent resistance.
Main Methods:
- Direct current passage across a single layer of Valonia ventricosa protoplasm impaled upon capillaries.
- Measurement of electrical resistance and polarization.
- Correlation of electrical measurements with five distinct stages of natural potential difference (P.D.).
Main Results:
- Five stages of P.D. were identified, showing varying resistance and polarization responses.
- A significant increase in apparent resistance (up to 10,000 ohms) was observed with inward current at a critical potential.
- Back EMF from polarization was found to largely account for apparent resistance, with calculated values up to 150 mV.
- Electrical capacitance of the protoplasm was estimated to be approximately 1 microfarad per cm².
Conclusions:
- The electrical resistance and polarization of Valonia ventricosa protoplasm are dynamic and stage-dependent.
- Back EMF generated by polarization is a key factor contributing to the measured electrical resistance.
- The study quantifies electrical capacitance, providing further insight into protoplasmic electrical properties.
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