But ultimately, glycolysis produces these byproduct molecules we call pyruvates. Now, glycolysis is an anaerobic process and what that means is it does not require oxygen to actually take place. So whether or not we have oxygen doesn't actually matter because glycolysis doesn't actually use oxygen. Now, in the absence of oxygen under anaerobic conditions, when we don't have plenty of oxygen present inside the cell, these Pyruvate molecules will undergo a process known as fermentation. Now, some cells in nature undergo alcohol fermentation and that produces ethanol from the Pyruvate. Other organisms, for instance, cells of our body undergo lactic acid fermentation and that transforms the Pyruvate into lactic acid or the conjugate base of lactic acid is lactate.