Final answer:
During anaerobic respiration, step two involves the conversion of pyruvate to lactate, often referred to as fermentation, which serves to regenerate NAD+. This process contrasts with aerobic respiration, where pyruvate enters the Krebs cycle, resulting in higher ATP production.
Step-by-step explanation:
In anaerobic respiration, specifically during step two of glycolysis (which can occur under anaerobic conditions), pyruvate is converted into lactate in a process known as fermentation. In this step, no oxygen is required, and the primary goal is to regenerate NAD+ so glycolysis can continue. No additional ATP is produced in this step, and the output is the formation of lactate (or lactic acid), with the regeneration of the electron carrier NAD+. This contrast greatly with aerobic respiration, where the presence of oxygen allows pyruvate to enter the Krebs cycle. This eliminates the need for fermentation, and instead, yields a large amount of ATP, carbon dioxide, and water as end products. Aerobic respiration involves complex biochemical pathways that lead to a more efficient energy production. The Krebs cycle and electron transport chain play central roles in aerobic respiration, producing NADH and FADH2 which shuttle electrons to the electron transport chain, resulting in the production of a significant amount of ATP.