Final answer:
The conversion of pyruvate to lactate, catalyzed by lactate dehydrogenase, occurs when oxygen is limited, allowing glycolysis to continue and providing a rapid source of ATP. Upon restoration of oxygen levels, lactate can be converted back to pyruvate for further energy production.
Step-by-step explanation:
The conversion of pyruvate to lactate occurs in the absence of oxygen, and the enzyme responsible for this reaction is lactate dehydrogenase (LDH). This process, known as anaerobic glycolysis, allows for the recycling of NADH back into NAD+, which is essential for glycolysis to continue, especially during high-energy-demanding situations like intense exercise. The production of lactate also helps maintain a low concentration of pyruvate, ensuring that glycolysis can proceed. Although this pathway generates less ATP than aerobic processes, it is crucial for short bursts of high-intensity exercise or in cells that lack mitochondria, such as red blood cells.
Moreover, the lactate produced can be transported to the liver, where it can be converted back to pyruvate or glucose through the Cori cycle, once oxygen is available. This re-conversion is important for longer-term energy balance and recovery after intense physical activity.