TCA Cycle: alpha-Ketoglutarate Dehydrogenase

Question 1

What reaction of the TCA Cycle is catalyzed by alpha-ketoglutarate dehydrogenase?

Answer 1

Oxidative decarboxylation of alpha-ketoglutarate

Question 2

Which reaction of the TCA Cycle produces the second CO2 generated by the cycle?

Answer 2

alpha-ketoglutarate dehydrogenase

Question 3

Which reaction of the TCA Cycle produces the second NADH generated by the cycle?

Answer 3

alpha-ketoglutarate dehydrogenase

Question 4

From which substrate of the TCA Cycle did the CO2 generated by alpha-ketoglutarate dehydrogenase originate from?

Answer 4

oxaloacetate

Question 5

When are the carbon atoms of acetyl-CoA oxidized to CO2?

Answer 5

In subsequent rounds of the cycle.

Question 6

What is the product of the reaction of the TCA Cycle catalyzed by alpha-ketoglutarate dehydrogenase? How many carbons does it have?

Answer 6

Succinyl-CoA; it has 4 carbons

Question 7

What enzyme complex does the alpha-ketoglutarate dehydrogenase complex chemically resemble?

Answer 7

The pyruvate dehydrogenase complex

Question 8

In what ways is the pyruvate dehydrogenase reaction of pyruvate to acetyl-CoA similar to the alpha-ketoglutarate dehydrogenase reaction of alpha-ketogluterate to succinyl-CoA?

Answer 8

1) Both include decarboxylation of an alpha-ketoacid
2) Both result in the formation of a thioester linkage with CoA that has high transfer potential
3) The reaction mechanisms are analogous, employing the same coenzymes and reaction steps.

Question 9

What are the electrons from the oxidation of the carbon atoms to CO2 in the isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase steps of the TCA Cycle captured as?

Answer 9

NADH