During alcohol fermentation, which occurs in yeast and some microorganisms, a net of 2 ATP molecules is produced per glucose molecule. This process begins with glycolysis, where glucose is broken down into pyruvate, yielding 2 ATP. The pyruvate is then converted into ethanol and carbon dioxide, but no additional ATP is generated during this step.
In lactic acid fermentation, which occurs in certain bacteria and animal muscle cells, a similar net of 2 ATP molecules is also produced per glucose molecule. Like alcohol fermentation, it starts with glycolysis, generating 2 ATP. The key difference is that the pyruvate produced is converted into lactic acid instead of ethanol and carbon dioxide.
In summary, both alcohol and lactic acid fermentation yield the same amount of ATP, with a total of 2 ATP produced from each glucose molecule during the fermentation processes.