One Resistor and Two Capacitors: An Electrical Engineer's Simple View of a Biological Cell

Based on a simple three-layer model, a network of three lumped elements of membrane capacitance, cytoplasm resistance, and cytoplasm capacitance was used to explain the so-called beta dispersion in the dielectric properties of biological cells hypothesized six decades ago. Using the simple network and without resorting to frequency-dependent permittivity, nondispersive membrane capacitance, cytoplasm resistance, and cytoplasm capacitance were extracted from microwave scattering parameters measured on single cells without the complication of electrode polarization or boundary layer. The extracted values, as small as 1 pF for the membrane capacitance, as large as 0.1 M for the cytoplasm resistance, and as small as 10 fF for the cytoplasm capacitance, agreed with the hypothesized values, as well as order-of-magnitude estimates from physical properties of cells.