A large fraction of the intermediary metabolism of eukaryotic cells occurs in the cytoplasm, and much of that has traditionally been considered to occur in what has been variously called the cytosol, cytoplasmic ground substance, hyaloplasm, or soluble phase of the cell (Anderson and Green 1967; Schneider 1976). These soluble metabolic pathways are generally believed to take place in solution within the cytoplasm, their operation and regulation occurring by random collisions of the participants of the pathway, governed by simple mass-action principles. According to this view, such pathways exist in that volume of the cytoplasm not occupied by the very considerable amount of architecture that is present, including the latest addition to an already crowded cytoplasm, the microtrabecular lattice (MTL) (Buckley and Porter 1975; Wolosewick and Porter 1979). For convenience I refer to that volume as the aqueous cytoplasm and use the term soluble enzyme to refer to those enzymes...