The Biology Project: Biochemistry

Metabolism Problem Set

Problem 7 Tutorial: Pyruvate / Lactate Ratio

Explain why in anaerobic cells the ratio of pyruvate/lactate is much less than 1 while under aerobic conditions the ratio of pyruvate/ acetate is much greater than 1.

Anaerobic conditions and lactic acid production

The glycolytic pathway produces pyruvate, which in the presence of oxygen will be further metabolized in the citric acid cycle to produce NADH and FADH2 for oxidative phosphorylation in the mitochondria. Normally, lactic acid will be low under these conditions.

In the absence of oxygen (anaerobic), pyruvate must be converted to lactic acid, the only reaction that can regenerate NAD+ allowing further glycolysis. The production of lactic acid only under anaerobic conditions explains why pyruvate/lactate is much less than 1 in anaerobic cells and much greater than one in aerobic cells.

The Biology Project
University of Arizona
Tuesday, August 20, 1996
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