A starship's Warp Propulsion System (WPS) consists of three major assemblies.
First, the matter/anti-matter reaction assembly (M/ARA) generates power from a controlled annililation of matter and antimatter.
Second, the power transfer conduits carry the energy plasma from the reaction chamber to the warp engine nacelles; at this point, power to run the bulk of the ship's non-propulsive systems is accessed by electro plasma system (EPS) taps.
Finally the plasma is directed to the warp engine nacelles, where it is used to create the subspace mechanics necessary for faster-than-light travel.
While a starship carries "traditional" fusion reactor fuel as well, the bulk of a ships systems depends upon the WPS for their operation.