Proton structure. Computer artwork showing the constituent parts of a proton. The proton is made up of three quarks (blue and white) held together by gluons (red). The quarks making up the proton are the down quark (arrow down) and two up quarks (arrow up). The down quark has a charge of -1/3, and each up quark has a charge of 2/3, giving the proton an overall electrical charge of +1. The gluons have no charge.