Representation of the use of FBA in metabolic modeling of an organism. The OF in panels a and b is maximizing the production of the biomass. The thickness of the arrows indicate the amount of flux, where a thicker arrow indicates a higher flux. When the production of lactate is manually altered in panel b, the flux distribution changes, whereby the flux of acetate, formate, ethanol, and biomass is lowered compared to panel a. Adapted after El-Semman et al.