What does burning fossil fuels and cellular respiration have in common?

Both release carbon into the atmosphere, but burning fossil fuels releases CO2 at a much greater amount. Both cellular respiration and combustion require a core fuel for the process to happen at all. This fuel is stored energy, and the entire process of combustion or respiration is to convert that energy from its stored state -- in the fuel -- to another state that the engine, either mechanical or bionic, can use to power its other operations. While fossil fuels and sugar molecules have very different structures, they both have a series of molecular bonds that the energy harvesting process will break apart.