  We study bipartite quantum discord as a manifestation of a multipartite
entanglement structure in the tripartite purified system. In particular, we
find that bipartite quantum discord necessarily manifests itself in the
presence of both bipartite and tripartite entanglement in the purification.
This allows one to understand the asymmetry of quantum discord (between D[A,B]
and D[B,A]) in terms of entanglement monogamy. As instructive special cases, we
study discord for qubits and Gaussian states in detail. As a result of this we
shed new light on a counterintuitive property of Gaussian states: the presence
of classical correlations necessarily requires the presence of quantum
correlations. Finally, our results also shed new light on a protocol for remote
activation of entanglement by a third party.
