Is the "soluble" phase of cells structured?

Evidence suggesting that small molecular-weight precursors as well as polymers such as proteins and RNA, are not homogeneously distributed in the "soluble" phase of the cell, and that there may be, on one hand, hitherto unidentified barriers to normal diffusion within the cell and, on the other, channels through which certain molecular species may move in the cell sap much faster than their diffusion coefficients will permit, is discussed. Some implications of such barriers and channels, if they exist, are stated.