 Both aspects are important in systems biology where one is often forced to aggregate elementary reactions into single stepreactions, and some models use relative concentrations (as a ratio of two concentrations or copy numbers). Previous derivations assume elementary reactions and rely on concentrations defined as copy numbers per unit volume. We demonstrate this 2MA approach with an application to the well established fission yeast cell cycle model.
<clarity>  Both aspects are important in systems biology where one is often forced to aggregate elementary reactions into single stepreactions, and some models use relative concentrations (as a ratio of two concentrations or copy numbers). Previous derivations assume elementary reactions and rely on concentrations defined as copy numbers per unit volume. We demonstrate this 2MA approach with an application to the well established fission yeast cell cycle model.
 Both aspects are important in systems biology where one is often forced to aggregate elementary reactions into single stepreactions, and some models use relative concentrations . We investigate the applicability of the 2MA approach with an application to the well established fission yeast cell cycle model.