Chemistry is an extremely important topic in physiology. Most physiological processes occur as the result of chemical changes that occur within the body. These changes include the influx/efflux of ions across a neuron's membrane, causing a signal to pass from one end to the other. Other examples include the storage of oxygen in the blood by a protein as it passes through the lungs for usage throughout the body.
The smallest building block of chemistry is the atom. The atom is subdivided into three atomic particles: the proton, the electron, and the neutron. Protons carry a positive charge. Electrons carry a negative charge. Neutrons have no charge at all.