  We present a simple model describing the assembly and disassembly of
heteropolymers consisting of two types of monomers $A$ and $B$. We prove that
no matter how we manipulate the concentrations of $A$ and $B$, it takes longer
than the exponential function of $d$ to synthesize a fixed amount of the
desired heteropolymer, where $d$ is the number of $A$-$B$ connections. We also
prove the decomposition time is linear for chain length $n$. When $d$ is
proportional to $n$, synthesis and destruction have an exponential asymmetry.
Our findings may facilitate research on the more general asymmetry of
operational hardness.
