Observed spectral profiles of emission lines from the corona are found to have widths exceeding the thermal line width. To investigate the physical mechanism behind this, we run a 3D MHD model of a single loop in which we partially resolve the turbulent motions within the loop and the substructures that form self-consistently in response to the driving by magneto-convection in the photosphere. The loop is modelled as a straightened-out magnetic flux tube with a shallow, self-consistently evolving convection zone layer at each end. This allows us to include the response of the chromosphere to heating events. From the model we synthesize spectral profiles of emission lines. We investigate the strongest heating events in the coronal loop and discuss the relation between footpoint motions and heating events as well as the effect of resulting flows on spectral diagnostics.