Final answer:
Fermentation is the pathway used in the absence of oxygen. It allows glycolysis to proceed, but with less ATP production. Fermentation is important in the production of alcoholic beverages and various food products.
Step-by-step explanation:
Fermentation is the pathway used in the absence of oxygen. It is a process called 'anaerobic respiration' that allows glycolysis to proceed, although much less ATP is obtained compared to normal cellular respiration. The end products of fermentation, such as ethanol or lactic acid, are more toxic and difficult to eliminate. Fermentation is important in the production of alcoholic beverages (by fungi and bacteria) and in the production of food products like sourdough, sauerkraut, and yogurt.