What changes when oxygen is unavailable?
When the oxygen supply is absent or insufficient, cells can continue respiration anaerobically.
- Oxygen is unavailable to accept electrons at the end of the electron transport chain.
- Electron transfer along the chain therefore ceases.
- Without the functioning electron transport chain, oxidative phosphorylation can no longer form ATP.
Glycolysis can still operate because it does not require oxygen directly. For it to continue, however, oxidised NAD must remain available.
Lactate fermentation
In mammalian cells, pyruvate can be converted to lactate.
Ethanol fermentation
In yeast cells, pyruvate can be converted to ethanol, with carbon dioxide released.