Krebs (TCA) Cycle

Question 1

What is the PDH complex?

Answer 1

Pyruvate Dehydrogenase complex

• 20-30 copies of pyruvate dehydrogenase
• 60 copies of dihydrolipoyl transacetylase
• Pyruvate to Acetyl CoA

Question 2

What cofactors and coenzymes are required for the PDH complex?

Answer 2

Coenzyme A
NAD+
FAD+
Lipoic acid
Thiamine pryophosphate (TPP)

Question 3

What is the yield of PDH?

Answer 3

2 NADH

Question 4

What is the yield of Krebs?

Answer 4

6 NADH, 2FADH2 and 2GTP

Question 5

What is the regulation of PDH complex initiated by?

Answer 5

Products - Acetyl CoA, NADH
Nucleotides - GTP (inhibits), AMP (activates)
Phosphorylation (inactivation)

Question 6

What is the PDH regulation enhanced by?

Answer 6

High ATP/ADP
High Acetyl CoA/CoA
NADH/NAD

Question 7

What inhibits the PDH complex regulation?

Answer 7

Pyruvate

Question 8

What is the overall reactions for Krebs Cycle?

Answer 8

Acetyl-CoA combines with oxaloacetate –> citric acid

2 CO2 removed to return to the oxaloacetate

Question 9

What 3 points is the Krebs Cycle regulated at?

Answer 9

1) Citrate synthase (ATP blocks)
2) Isocitrate dehydrogenase (ATP blocks)
3) Alpha-ketoglutarate dehydrogenase (succinyl CoA and NADH blocks)