  We extend our relativistic quark model to the study of the decay Lambda_b ->
Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry
constraints at order 1/mQ^2. We isolate a strong dependence on a parameter
which measures the relative distortion in the light-quark wave functions of the
Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be
small. The dependence on a corresponding parameter in the meson case leads to
large 1/mQ^2 corrections.
