In one embodiment of the invention, a replaceable electrosurgical end effector cartridge is provided to couple to a mechanical wrist of a surgical instrument for a robotic surgical system. The replaceable electrosurgical end effector cartridge includes two end effectors, a fastener to rotatably couple the two end effectors together, and a cam mechanism. At least one of the two end effectors is a moveable end effector having a jaw portion, an off-center portion, and a base portion. The cam mechanism is coupled to the base portion of the at least one moveable end effector to pivot it about the fastener to open and close the jaw portion of the at least one moveable end effector with respect to the other.