Plastocyanin (CuPc) is reduced (an electron is added) by cytochrome f according to the following reaction:
:CuPc + e → CuPc
After dissociation, CuPc diffuses through the lumen space until recognition/binding occurs with P700, at which point P700 oxidizes CuPc according to the following reaction:
:CuPc → CuPc + e
The redox potential is about 370 mV and the isoelectric pH is about 4.