It is known that mitochondria play a crucial role in the handling of calcium by cardiac cells during the excitation-contraction cycle. However, the precise characterization of this role is still under debate. With this intent, a collection of mathematical models have been developed, but they generally show a level of complexity that is not compatible with inverse problem techniques required for calibration with experimental data. Their large number of equations and parameters can also lead to transcription mistakes that can be found in the literature. In this paper we apply a similar methodology as Bertram et al.in [1] to propose a simple model that is derived from the base equations that constitute the origin of most mitochondrial models [2]. Our model describes the main features of the mitochon-drial activity with 6 equations and ∼30 parameters, which we will eventually reduce in a forthcoming sensitivity analysis .