I found this information:
Anaerobic respiration begins the same way as fermentation. The first step is still glycolysis, and it still creates 2 ATP from one carbohydrate molecule. However, instead of ending with glycolysis, as fermentation does, anaerobic respiration creates pyruvate and then continues on the same path as aerobic respiration.
After making a molecule called acetyl coenzyme A, it continues to the citric acid cycle. More electron carriers are made and then everything ends up at the electron transport chain. The electron carriers deposit the electrons at the beginning of the chain and then, through a process called chemiosmosis, produce many ATP. For the electron transport chain to continue working, there must be a final electron acceptor. If that acceptor is oxygen, the process is considered aerobic respiration.
Scientists believe that fermentation and anaerobic respiration are older processes than aerobic respiration.
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