what are alcohol fermentation and lactic acid fermentation, and what are their differences?

Answer 1

They both occur when an organism respires anaerobically. Usually respiration has three stages, but these two (lactic acid and alcohol fermentation) take place in the absence of oxygen, so only the first stage glycolysis takes place. At the end of glycolysis a 3 carbon compound pyruvate is formed, and this is waste if it cannot be used in the next stages of respiration, that require oxygen. Different organisms convert the waste pyruvate into different compounds, mammals produce lactic acid while yeast produces alcohol.