Final answer:
Fermentation allows glycolysis to proceed by regenerating NAD+ in the absence of oxygen, which is essential for ATP production in anaerobic conditions. It includes alcoholic and lactic acid fermentation, and while it yields less ATP than aerobic respiration, it is vital for cell survival without oxygen.
Step-by-step explanation:
Fermentation is a critical biological process that allows cells to produce energy in the absence of oxygen. When oxygen is not available, organisms rely on fermentation to regenerate NAD+ from NADH, ensuring that glycolysis can continue and ATP can be harvested from the breakdown of glucose.
Alcoholic fermentation and lactic acid fermentation are two common types, each resulting in different end products and used by various organisms, including humans. In alcoholic fermentation, pyruvate from glycolysis is converted to ethanol, while lactic acid fermentation produces lactate. Both types are essential for ATP production when oxygen levels are low, such as during vigorous exercise when muscle cells may not have enough oxygen. It's important to note that fermentation is less efficient than aerobic respiration, yielding only 2 ATP from glycolysis, compared to the 36-38 ATP that can be produced with oxygen. However, without fermentation, cells would be unable to continue glycolysis under anaerobic conditions and would not survive.