Question

Pyruvate dehydrogenase deficiency is a genetic disease most commonly linked to a mutation in the a -subunit of the mitochondrial enzyme that causes the enzyme to cease functioning. As a result of the mutation, affected individuals build up dangerous amounts of lactic acid. Which of the following best explains the buildup of lactic acid in individuals with the mutation?
a. Cells use lactic acid to shunt electrons from pyruvate to the electron transport chain in the mitochondria.
b. Cells undergo glycolysis because there is a buildup of pyruvate in affected individuals.
c. Cells cannot transport pyruvate to the mitochondria in the absence of pyruvate dehydrogenase activity, so the pyruvate is broken down to lactic acid and ethanol
d. Cells undergo fermentation because pyruvate cannot be metabolized to proceed into the Krebs cycle.

Answer 1

Answer: The correct option is D ( Cells undergo fermentation because pyruvate cannot be metabolized to proceed into the Krebs cycle).

Explanation:

Pyruvate dehydrogenase is the enzyme that converts pyruvate to acetyl CoA which enters the Krebs cycle in glucose metabolism. The deficiency of Pyruvate dehydrogenase can be caused by genetic origin most commonly linked to a mutation in the a -subunit of the mitochondrial enzyme that causes the enzyme to cease functioning. As a result of the mutation, affected individuals build up dangerous amounts of lactic acid.

The increase in the level of lactic acid occurs due to the Increased action of lactate dehydrogenase enzyme. In the absence of Pyruvate dehydrogenase enzyme, the level of blood pyruvate increases. Excess pyruvate is then converted to lactic acid by lactate dehydrogenase enzyme in a process called lactic fermentation. This results in a buildup of lactic acid in the blood leading to a condition called lactic acidosis .

Therefore, cells undergo fermentation because pyruvate cannot be metabolized to proceed into the Krebs cycle.