When is lactate produced from pyruvate?

Lactate is produced from pyruvate primarily in the absence of oxygen, a process known as anaerobic glycolysis. When oxygen levels are low, such as during intense exercise or in certain pathological conditions, cells are unable to conduct aerobic respiration effectively. Instead, they rely on anaerobic pathways to generate energy.

Under these conditions, pyruvate, which is the end product of glycolysis, is converted to lactate by the enzyme lactate dehydrogenase. This conversion helps regenerate NAD+, which is essential for glycolysis to continue producing ATP in the absence of sufficient oxygen.

Oxygen typically allows for the complete oxidation of pyruvate in the mitochondria, leading to the citric acid cycle and ultimately yielding more ATP. Therefore, the production of lactate signifies a shift to anaerobic metabolism, where energy demands exceed the capacity for oxidative phosphorylation due to low oxygen availability.