Incorrect units in simple reaction in SimBiology?

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I wonder why SimBiology does not detect any issues in the following model.
A cell, Cell, is producing signaling molecule, Sig, with following reaction:
Reaction 1: Cell -> Cell + Sig: kprod * Cell
Reaction 2: Sig -> null: kel*Sig
Units are as follows
Cell [molecule]
Sig [mole / milliliter]
kprod [gram / (molecule * day)]
kel [1/day]
The ODE seems to be correct: d(Sig)/dt = 1/Comp1*((kprod*Cell) - ((kel*Sig)*Comp1)) BUT there should be an error as the units don't match. Any comments would be very appreciated!
See below the screenshort of the model and settings plus sbproj.
EDIT: adding molecular mass into the production rate: kprod / MM * Cell solves the unit Issue of course, but I would expect that such inconsistency would be detected by the software. PS: MM [g/mol]

Accepted Answer

Arthur Goldsipe
Arthur Goldsipe on 12 Jul 2022
This is a bug in SimBiology. SimBiology checks that all species participating in a reaction have dimensionally consistent units. For example, you would see an error if one species had units of gram while another had units of molecule. But SimBiology does not currently check that the reaction rate's units are dimensionally consistent with these species units.
I'll create a bug report so that we can fix this in a future release. Thanks again for bringing this to our attention.
Arthur Goldsipe
Arthur Goldsipe on 13 Jul 2022
Thanks for sharing. I think I'd heard about a similar pain from one other user several years ago. Given that low frequency, we haven't prioritized making this workflow easier. But I'll make sure to note your feedback in our enhancement database so that we can reevaluate the priority of fixing this.

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