unit dimensional analysis problems
4 次查看(过去 30 天)
显示 更早的评论
I am tyring to build a model using irreversible and reversible mass action kinetics (Matlab R2023a). My species units are all in molarity and I follow the reaction rate constant units of paper.However, Simbiology repeatedly fails dimensional analysis and give me those two error meeage:
'Quantities of different dimensions cannot be added or subtracted'
'Reaction rate units should result in dimensions of either concentration/time or substance/time'
for the first one error message My reactions are all quite straight forward:
A + 5 B <-> AB ( kf : 1/molarity*second , kr : 1/second)
for second error message the reaction is like this:
FGUvsXcD + 9 ATP -> 9 FD + 9 UvsX + 9 AMP + 9 PPi ( kf :1/second)
so I don't understand why this is causing such problems.
0 个评论
回答(2 个)
Arthur Goldsipe
2023-9-18
If your reactions are using mass action kinetics, then the units you report for "kf" are not correct. For the first reaction, the forward rate will be kf*[A]*[B]^5. Note the exponent of 5. So I would expect kf to have units of 1/(molarity^5*second).
If that doesn't solve your problem, can you share the project or code that reproduces the issue? It's often difficult to diagnose what's going on without reproduction steps.
0 个评论
Lo
2023-9-19
编辑:Lo
2023-9-19
3 个评论
Arthur Goldsipe
2023-9-20
You can't, for the mass action kinetics you've specified. The units on the rate constant are constrained by the form of the reaction rate.
Your question makes me wonder if you have made a mistake in how you chose to model this reaction and its rate. kf units of 1/(molarity*second) are associated with a bimolecular mass action reaction like "A + B -> AB".
When you choose to model the reaction "A + 5 B -> AB" with mass action kinetics, the reaction rate is "kf*A*B^5". Furthermore, the dimensions of this reaction rate must either be concentration/time (for example, molarity/second) or amount/time (for example, mole/second). Since you seem to be working in concentrations, I assume you want A and B to have units of molarity and the reaction rate to have units of molarity/second. And this is how I "derived" that the units of kf needed to be 1/(molarity^5*second).
社区
更多回答在 SimBiology Community
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 QSP, PKPD, and Systems Biology 的更多信息
产品
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!