U3 AOS2 Topic 6: Anaerobic Fermentation

Anaerobic fermentation involves the breakdown of glucose to produce ATP in the absence of oxygen but energy production in this case is less than that of aerobic respiration. Anaerobic fermentation occurs in cytosol of yeast and animal cells but both involve different pathways. Glycolysis is same in both aerobic and anaerobic respiration but due to lack of oxygen there is no krebs cycle and electron transport chain. Instead, there are different pathways after glycolysis to recycle NADH produced in glycolysis back to NAD+.

Anaerobic fermentation in animals:

After glycolysis, the pyruvate molecules undergo lactic acid fermentation in which pyruvate is broken down into lactic acid and NADH is converted back into NAD+ to be reutilized in glycolysis.

Anaerobic fermentation in yeasts:

After glycolysis, the pyruvate molecules undergo ethanol fermentation. Pyruvate is converted into ethanol and CO2 and NADH is converted back into NAD+ to be reutilized in glycolysis. This process involves two steps. First step is completed when pyruvic acid is converted into acetaldehyde and CO2 is liberated whereas, second step involves the conversion of acetaldehyde into ethanol and NADH is converted into NAD+.