The Energy of Life:

Although gravitational force is important for large objects like us, it has no significance for small objects like cells. The electric force is – roughly – one thousand million million million million million million times stronger than the gravitational force and is the only force that matters at the level of molecules and cells. Gravitational force causes attraction – that is, two objects will accelerate towards each other. But the electric force causes either repulsion or attraction depending on whether the matter carries the same or different charges: opposites attract, likes repel. The electron carries a negative charge: the proton a positive charge. Everything, including our bodies, can be considered made up of different arrangements of protons and electrons. (There are also neutrons, but they have no charge, and behave like an electron and a proton stuck tightly together.) Everyday objects are made up of approximately equal numbers of electrons and protons. If this were not so, an excess of positive or negative charge would create a huge force pushing out (or exploding) the extra charge, leaving a roughly neutral group of electrons and protons. The power of the electric force is truly immense. If two people, standing at arm’s length, each had one per cent more electrons than protons in their bodies, they would be blown apart by an electric force sufficient to move the weight of the entire earth.