You know, RWP, we all talk about pathways because we draw biochemical reactions in a chain from beginning precursors to end products. But there are no "pathways", per se inside a cell, just a pile of catalysts and reactants floating around reacting. The "pathways" thingy just helps us visualize what's happening.
Chemical or biochemical products of cell metabolism don't walk down a path. There may be "helpers" along the way to make sure things are assembled correctly but that hardly constitutes a path.
IDCists will reify anything they can get their minds wrapped in... I mean around.
Hmmm. Say you have a muscle actively exercising. You start with glycogen, and turn it into pyruvate. There are around a dozen chemical steps between glycogen and pyruvate, almost all with specific enzymes to catalyse them, and 99% of the glucose units in the glycogen follow those steps in sequence. It may not be a physical pathway, but I think 'pathway' is a valid analogy.
I thought they often were wrapped in a vesicle and "tagged" for transport to specific destinations.