Comparing aerobic and anaerobic respirationSpec 2.36
In short
Aerobic respiration needs oxygen and releases much more energy per glucose molecule than anaerobic respiration, because glucose is completely broken down to carbon dioxide and water. Anaerobic respiration needs no oxygen and only partly breaks down glucose, making lactic acid in animals or ethanol and carbon dioxide in plants and yeast. Both make ATP.
| 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 release energy from glucose to make ATP.
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 IGCSE Biology (4BI1) specification · Updated October 2026