Mitochondria do not exist in prokaryotes. Instead, these organisms, which include bacteria and archaea, carry out their energy production in their cell membranes. Mitochondria are double-membraned organelles found in eukaryotic cells, where they play a crucial role in cellular respiration and energy (ATP) production through oxidative phosphorylation.
In prokaryotes, the processes that occur in mitochondria take place across the plasma membrane. For instance, prokaryotic cells utilize a series of proteins embedded in their membrane to create a proton gradient, which is essential for ATP production. This allows them to generate energy, albeit through different mechanisms than eukaryotic cells.