  For two molecules to react they first have to meet. Yet, reaction times are
rarely on par with the first-passage times that govern such molecular
encounters. A prime reason for this discrepancy is stochastic transitions
between reactive and non-reactive molecular states, which results in effective
gating of product formation and altered reaction kinetics. To better understand
this phenomenon we develop a unifying approach to gated reactions on networks.
We first show that the mean and distribution of the gated reaction time can
always be expressed in terms of ungated first-passage and return times. This
relation between gated and ungated kinetics is then explored to reveal
universal features of gated reactions. The latter are exemplified using a
diverse set of case studies which are also used to expose the exotic kinetics
that arises due to molecular gating.
