9.4 Pyruvate Dehydrogenase

Question 1

What are the two options for when pyruvate from aerobic glycosis enters mitochondria?

Answer 1

• converted to acetyl-CoA for entry into the citric acid cycle if ATP is needed, or for fatty acid synthesis if sufficient ATP is present

Question 2

Pyruvate dehydrogenase complex (PDH)

Answer 2

• is irreversible
• cannot be used to convert acetyl-CoA to pyruvate or to glucose
• Pyruvate dehydrogenase in the liver is activated by insulin
• Pyruvate dehydrogenase is inhibited by its product acetyl-CoA

Question 3

What’re the 3 possible fates for pyruvate?

Answer 3

• conversion to acetyl-CoA by PDH
• conversion to lactate by lactate dehydrogenase, or
• conversion to oxaloacetate by pyruvate carboxylase.

Question 4

Cofactors and Coenzymes for PDH?

Answer 4

thiamine pyrophosphate, lipoic acid, CoA, FAD, and NAD+

Question 5

How does acetyl-Coa inhibit Pyruvate dehydrogenase?

Answer 5

buildup of acetyl-CoA (which happens during β-oxidation) causes a shift in metabolism: pyruvate is no longer converted into acetyl-CoA (to enter the
citric acid cycle), but rather into oxaloacetate (to enter gluconeogenesis).