Energetics of Pathways, con’t.
If Q is less than about 0.05 K, this step of
the pathway is removed from equilibrium.
The rate through such a step will vary by
changing the activity of the enzyme.
Such a step is a rate limiting step.
Most pathway regulation occurs at such steps.
(Regulation at equilibrium steps does occur,
usually by availability of a coenzyme
cosubtrate.)