Cellular respiration is a process by which cells convert sugars from the environment to energy. The difference between the two types -- aerobic and anaerobic -- is that aerobic respiration relies on oxygen. In aerobic respiration, cells convert glucose and oxygen to carbon dioxide and water. Key to its high energy production is a cellular innovation, the electron transport chain, that allows energy to be safely harvested from oxygen.
One glucose molecule plus six molecules of oxygen gas are transformed into six carbon dioxide molecules plus six water molecules. Chemical energy is released by the reaction.
In scientific notation, the reaction is written:
C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + (energy) 36 ATP
Cellular respiration allows cells to convert food energy (glucose) into chemical energy in the form of ATP, or adenosine triphosphate.
ATP is the form of chemical energy cells require to perform work. ATP allows cells to grow, reproduce and make molecules.
Cellular respiration has the opposite outcome to that of photosynthesis, in which plants produce oxygen and glucose. Because oxygen and carbon dioxide are exchanged during these two reactions, photosynthesis and cellular respiration are part of the processes that balance atmospheric concentrations of these gases.