  Biochemical models that exhibit bistability are of interest to biologists and
mathematicians alike. Chemical reaction network theory can provide sufficient
conditions for the existence of bistability, and on the other hand can rule out
the possibility of multiple steady states. Understanding small networks is
important because the existence of multiple steady states in a subnetwork of a
biochemical model can sometimes be lifted to establish multistationarity in the
larger network. This paper establishes the smallest reversible, mass-preserving
network that admits bistability and determines the semi-algebraic set of
parameters for which more than one steady state exists.
