In cellular respiration, glucose is broken down by reacting it with oxygen to produce carbon dioxide and water.
C6H12O6 + 6O2 -> 6CO2 + 6H2O
In fossil fuels, methane or any other fuel is combusted using oxygen.
CH4 + 2O2 -> CO2 + 2H2O
The combustion of glucose happens in cellular respiration.
