Read Fermentation and NAD+ Recycling
Fermentation regenerates NAD+ without an electron-transport chain, allowing glycolysis to continue when oxygen is unavailable.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Trace the redox cycle
Glycolysis reduces NAD+ to NADH. In lactic fermentation, pyruvate accepts electrons to form lactate; in alcoholic fermentation, acetaldehyde is reduced to ethanol. NAD+ is regenerated in both routes.
Compare energy yields
Fermentation only partially oxidises glucose and yields far less ATP than aerobic respiration. When oxygen becomes available to yeast, aerobic metabolism can make more ATP per glucose, so glucose use for the same energy demand falls.
Use careful wording
Fermentation is distinct from anaerobic respiration that uses an external terminal electron acceptor and an electron-transport chain. Organisms and cells can switch pathways according to conditions.
OlympIQ exam lens
- ✓NADH is reoxidised to NAD+.
- ✓Lactate pathway releases no CO2; alcoholic pathway does.
- ✓Fermentation yields little ATP compared with aerobic oxidation.
- ✓Oxygen can suppress fermentation in yeast (Pasteur effect).
Do not equate fermentation with every form of anaerobic respiration; anaerobic ETS can use a non-oxygen acceptor.
Ready to try the pattern?
100% coverage across the 7 linked questions.
Practise 7 linked questions