Comparison of the metabolic reactions in the three cell-specific reactions. (A) The three cell-specific reconstructions have a similar number of reactions in most subsystems. It is interesting to note that the AM has much fewer amino acid metabolic reactions and the MM fewer lipid metabolic reactions. The reaction number difference is in accordance with the cell composition differences. The HM has the most reactions in most subsystems due to the liver's varied metabolic states. For comparison, the number of reactions in each subsystem is also provided for Recon 1. (B) The three cell-specific reconstructions share the most intracellular metabolic reactions that seem to be a "core" group of reactions required for most human cells. The rest of the reactions are mostly exclusive. The AM and MM have very little reaction similarity that is not also found in the HM.