Anaerobic use of Pyruvate

The last step of glycolysis leaves us with two 3-carbon molecules, called pyruvate. The fate of pyruvate depends on the availability of oxygen. If oxygen is available, then pyruvate is shuttled into the mitochondria and continues through several more biochemical reactions called the "Citric Acid Cycle." This is called aerobic metabolism. If oxygen is not available in sufficient quantity to the cell, then pyruvate goes through a reduction reaction that results in the production of Lactate (see below figure 6). This is called anaerobic metabolism.

Reduction of Pyruvate

Image created by JS at BYU Idaho F2013.

Aerobic use of Pyruvate

When there is enough oxygen available to the cell, pyruvate crosses the mitochondrial membrane and is quickly converted to Acetyl CoA. Acetyl CoA enters the Citric Acid Cycle where CoA is removed and the acetate is added to a 4 carbon molecule to make a 6 carbon molecule called “Citric Acid.” As the biochemical steps of the Citric Acid Cycle continue (See figure 9), 2 more carbons are lost as CO2 and so ultimately all the carbons of pyruvate are lost as CO2. After 2 pyruvates complete the citric acid cycle, all the carbons of the original Glucose molecule have been released as CO2.

Pyruvate dehydrogenase

Image created by JS at BYU Idaho F2013.

The image above shows the conversion of Pyruvate to Acetyl CoA occurs in the mitochondria and results in the loss of a Carbon as CO­2 and the creation of Acetyl CoA. 

**You may use the buttons below to go to the next or previous reading in this Module**