TCA Cycle Flashcards
1
Q
What is the pyruvate dehydrogenase complex?
A
- requires oxidative decarboxylation by Pyruvate Dehydrogenase Complex (located in the mitochondrial matrix)
- pyruvate + NAD+ + CoA –> acetyl-CoA + CO2 + NADH
- inhibited by acetyl CoA and NADH (product inhibition that activate a kinase that inhibits the complex)
2
Q
What are the 3 enzymes of the pyruvate dehydrogenase complex?
A
- E1: pyruvate dehydrogenase (rate limiting step) (thiamine pyrophosphate [TPP] needed as cofactor)
- E2: requires CoA and lipoic acid as cofactors (makes acetyl CoA so that why CoA is needed)
- E3: requires FAD and NAD+ as cofactors
3
Q
How is the pyruvate dehydrogenase complex regulated?
A
- phosphorylation through PDH kinase inhibits E1, while dephosphorylation through PDH phosphatase activates E1
- PDH Kinase is activated (inactivation of E1) by ATP, acetyl-CoA and NADH
- PDH Phosphatase is inhibited (activates E1) by pyruvate
4
Q
What 3 enzymes are involved in TCA cycle regulation?
A
- citrate synthase
- isocitrate dehydrogenase
- alpha-ketoglutarate dehydrogenase
5
Q
What does citrate synthase do?
A
- converts oxaloacetate to citrate
- inhibited by its product (citrate)
6
Q
What does isocitrate dehydrogenase do?
A
- MAJOR REGULATOR (isocitrate to α-ketoglutarate)
- makes first NADH and first CO2 release
- allosterically activated by ADP and Ca2+; inhibited by ATP and NADH
7
Q
What does the alpha ketoglutarate dehydrogenase complex to?
A
- (α-ketoglutarate-succinyl CoA)
- makes second NADH and second CO2 release
- required coenzymes: thiamine pyrophosphate, lipoic acid, FAD, NAD+ and CoA
- inhibited by its products: NADH and Succinyl CoA
- activated by Ca2+
8
Q
What are the products from one acetyl CoA?
A
3 NADH
1 FADH2
1 GTP (Substrate level phosphorylation
2 CO2
x2 for glucose because every glucose will produce 1 acetyl CoA
9
Q
Where does the TCA cycle take place?
A
Mitochondrial matrix
