There are two types of respiration: anaerobic, which does not require oxygen, and aerobic, which requires oxygen. The energy released by respiration is used by living organisms for their life processes.
Anaerobic respiration happens in both animals and plants. Anaerobic respiration discharges about 5% of the energy delivered by aerobic respiration per glucose molecule.
Without oxygen, anaerobic processes leave most of the ATP-generating supplies in the waste products, such as lactic acid in animals, or alcohol and CO2 in plants and yeast. The difference in products is the primary difference between the two.
`C_6H_12O_6` (glucose) -> `2C_3H_6O_3` (lactic acid)
`C_6H_12O_6` (glucose) -> `2C_2H_5OH ` (ethanol) + `2CO_2`
When glucose molecules break down in anaerobic respiration, the pyruvate stays in cells. The lactic acid needs to be oxidized to water and carbon dioxide later. In yeast, pyruvate is first converted to ethanol and then to ethanol.