  We propose a model for the dynamics of a probe embedded in a living cell,
where both thermal fluctuations and nonequilibrium activity coexist. The model
is based on a confining harmonic potential describing the elastic cytoskeletal
matrix, which undergoes random active hops as a result of the nonequilibrium
rearrangements within the cell. We describe the probe's statistics and we bring
forth quantities affected by the nonequilibrium activity. We find an excellent
agreement between the predictions of our model and experimental results for
tracers inside living cells. Finally, we exploit our model to arrive at
quantitative predictions for the parameters characterizing nonequilibrium
activity, such as the typical time scale of the activity and the amplitude of
the active fluctuations.
