We optoelectronically functionalize carbon nanotubes (CNTs) with the photosynthetic reaction center photosystem I (PSI) according to three different on-chip chemical routes. The PSI is bound to the CNTs via covalent, hydrogen, or electrostatic bonds. Our approach allows the electrical contact of single PSI-CNT hybrid systems where the orientation of the PSI with respect to the CNTs depends on the binding mechanism. Our data are consistent with the interpretation that if the PSI is anchored with its internal electron transport path perpendicular to CNTs, the optical excitation of the PSI leads to an enhanced photoconductance of the hybrid system.