Methods are provided herein for: calculating cell growth rates in various environments and genetic backgrounds; calculating the order of substrate utilization from a defined growth medium; calculating metabolic flux reorganization in various environments and at various growth rates; and calculating the maximum metabolic rate and optimal metabolite concentrations and enzyme activities by applying a computational optimization method to a kinetic model of a metabolic pathway. The optimization methods use intracellular molecular crowding parameters and/or well as kinetic rates to assist in modeling metabolic activity.