Structure of the nucleon in the unquenched quark model

We discuss the flavor asymmetry of the nucleon sea and the spin content of the proton in an unquenched quark model. It is shown that the inclusion of hadron loops leads automatically to an excess of d-bar over baru and introduces a sizeable contribution of orbital angular momentum to the spin of the proton and the Λ hyperon. Special attention is paid to the symmetries of the unquenched quark model.