Oxysomes or $\mathrm{F}_0-\mathrm{F}_1$ particles are present on the inner mitochondrial membrane. The $\mathrm{F}_1$ headpiece of oxysome functions as ATP-synthetase which synthesises ATP from ADP and ip (inorganic phosphate) using energy from proton gradient or ATP synthetase becomes active in ATP formation only when there is a proton gradient having high concentration of protons on $\mathrm{F}_0$ side (base) as compared to $F_1$ side (head piece) of $F_0-F_1$ particles or oxysomes.