Proteins contain acidic and basic residues which would be ionized in aqueous solution. Favorable charge-dipole interactions stabilize charges in water. Thus, charged groups on the protein surface helps them remain soluable. A small, but significant number of ionizable residues are buried in the protein. I will describe how electrostatic analysis can be used to calculate the equilibrium ionization state of these residues by computing the interactions amongst charges and dipoles in the protein. In addition, I will describe how these buried acidic and basic groups function in pumping protons across cell membranes in proteins such as bacteriorhodopsin or facilitate electron transfers in proteins like photosynthetic reaction centers.