Yes, cells do have voltage, but not in the way you might initially think. The statement "cells have voltage" is imprecise. It's more accurate to say that there is a voltage difference or electrical potential difference across a cell's membrane. This is due to an uneven distribution of ions (like sodium, potassium, and chloride) inside and outside the cell. This difference is crucial for many cellular processes.
Understanding Cellular Voltage
- Membrane Potential: Cells maintain an electrical potential across their membranes, typically ranging from -40mV to -90mV (millivolts). This is called the resting membrane potential. The negative sign indicates that the inside of the cell is more negatively charged relative to the outside.
- Ion Gradients: This potential difference is established and maintained by ion pumps and channels in the cell membrane. These pumps actively transport ions against their concentration gradients, creating an imbalance of charge.
- Variability: The exact voltage across a cell's membrane varies considerably depending on the cell type, its environment, and its activity. A generalized value like 0.07V is an oversimplification and shouldn't be taken as a universal constant. The statement that a human cell generates 0.07 volts of electricity is inaccurate without specifying the location of the measurement (across the membrane, and which cell).
- Voltage-Gated Channels: Many cellular processes, such as nerve impulses and muscle contractions, rely on voltage-gated ion channels. These channels open or close in response to changes in the membrane potential, allowing ions to flow and further altering the voltage. Voltage-dependent ion channels in glial cells show that even the microenvironment of a cell influences its voltage. Voltage-Gated Ion Channels in Human Pancreatic β-Cells are an example of how this voltage difference is functionally important.
- Voltage Gradients: Voltage isn't uniform within a cell. Yes, you can also have voltage gradients within cells and outside cells, though these quickly equalize except across membranes.
The idea of harnessing the combined voltage of all cells in a human body is flawed. These voltages are not additive in a straightforward manner. The voltages are across membranes and are not connected in series to create a large voltage.
