  The representation of a biochemical network as a graph is the coarsest level
of description in cellular biochemistry. By studying the network structure one
can draw conclusions on the large scale organisation of the biochemical
processes. We describe methods how one can extract hierarchies of subnetworks,
how these can be interpreted and further deconstructed to find autonomous
subnetworks. The large-scale organisation we find is characterised by a tightly
connected core surrounded by increasingly loosely connected substrates.
