Metabolism 3: Krebs/CAC/TCA

Question 1

Name the 3 sources of Acetyl-CoA

Answer 1

1. Glycogen –> Glycogenolysis –> Glucose –> Glycolysis –> Pyruvate –> PDH (oxidation) –> Acetyl-CoA
2. Triglycerides –> Lipolysis –> FFAs –> B-oxidation –> Acetyl-CoA
3. Proteins –> Proteolysis –> a.a.’s –> Deamination and oxidation –> Acetyl-CoA

Question 2

Name the 3 fates of Acetyl-CoA

Answer 2

1. TCA
2. Ketone bodies
3. Sterols, FAs

Question 3

How is PDH deficiency caused? What are symptoms? Treatments?

Answer 3

• Most common cause is E1 alpha subunit mutation (X-linked dominant)
• Childhood symptoms: increased serum lactate, pyruvate, alanine –> causes chronic lactic acidosis
• Treatment: diet supplement of thiamine, carnitine, lipoic acids or an inhibitor of protein kinase subunit of PDH (dichloroacetate)

Question 4

How many ATP are produced per CAC?

Answer 4

9 ATP + 1 GTP = 10 ATP

Question 5

What are the allosteric effectors in the fine control of the CAC and their enzymes (2)?

Answer 5

1. Isocitrate Dehydrogenase: activated by ADP, inhibited by ATP, NADH
2. a-Ketoglutarate Dehydrogenase: activated by Ca2+, inhibited by ATP, NADH, GTP, Succinyl-CoA