Exam 3: The Citric Acid Cycle

Question 1

What is the chemical equation for the reactants and products of the citric acid cylce?

Answer 1

Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O —> 2CO2 + 3NADH + FADH2 + GTP + CoA + 3H+

Question 2

List the reactants and products of the citric acid cycle in order.

Answer 2

Acetyl-CoA + Oxaloacetate > Citrate > Isocitrate > a-Ketoglutarate > Succinyl-CoA > Succinate > Fumarate > Carbanion transition state > L-Malate > Oxaloacetate

Question 3

What are the three main stages of cellular respiration?

Answer 3

1. Acetyl CoA production
2. Acetyl CoA oxidation
3. Electron transfer and oxidative phosphorylation

Question 4

Acetyl CoA is produced from what?

Answer 4

Pyruvate.

Question 5

What does Coenzyme A do in the production of Acetyl CoA?

Answer 5

It is a reactive thiol group that reacts to bind with the acetyl aldehyde.

Question 6

Explain E1, E2, E3 in pyruvate dehydrogenase complex (PDC).

Answer 6

PDC is a large multienzyme complex.

E1 decarboxylates pyruvate to an aldehyde and then oxidizes the aldehyde to a thioester.

E2 forms acetyl-CoA.

E3 reoxidizes the lipoyl cofactor from E1 with reduction of FAD to FADH2 and regenerates the oxidized FAD cofactor to form NADH.

Question 7

What is generated in acetyl-CoAs oxidation in cellular respiration?

Answer 7

GTP, NADH, and FADH2 are generated.

Question 8

A lot of ______ is generated from electron transfer and the oxidative phosphorylation of cellular respiration.

Answer 8

ATP.

Question 9

What are anaplerotic reactions?

Answer 9

Reactions that replenish TCA cycle intermediates that have been extracted for biosynthesis.

Question 10

What are the anaplerotic reactions in the TCA cycle?

Answer 10

1. Pyruvate to Oxaloacetate
2. Aspartate to Oxaloacetate
3. Glutamate to a-Ketoglutarate
4. B-Oxidized of fatty acids to succinyl-CoA
5. Adenylsuccinate to fumarate