Comparing aerobic and anaerobic respirationSpec 8.10
In short
Aerobic respiration needs oxygen and completely breaks down glucose, releasing a large amount of energy per glucose molecule. Anaerobic respiration does not need oxygen and only partly breaks down glucose, so it releases much less energy. Both are exothermic. Anaerobic respiration happens when oxygen is not available, for example in muscles during vigorous exercise.
| Aerobic respiration | Anaerobic respiration | |
|---|---|---|
| Oxygen needed? | Yes | No |
| Glucose breakdown | Complete breakdown | Incomplete breakdown |
| Energy released | A large amount per glucose molecule | Much less per glucose molecule |
| Products in animals | Carbon dioxide and water | Lactic acid |
| Products in plants and yeast | Carbon dioxide and water | Ethanol and carbon dioxide |
| When it happens | Whenever enough oxygen is available | When oxygen is not available, for example in muscles during vigorous exercise |
Aerobic respiration releases much more energy because glucose is completely broken down. Anaerobic respiration releases less energy because glucose is only partly broken down. Both types of respiration are exothermic and both release energy from glucose.
A comparison needs both sides in the same sentence, for example: aerobic respiration releases more energy per glucose than anaerobic respiration.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026