Lecture 24: TCA Cycle Flashcards
Three steps in formation of Acetyl CoA from pyruvate
Decarboxylation
Oxidation
Transfer to CoA
NADH is produced
How does pyruvate enter the mitochondria, and what decarboxylates it once inside
Mitochondrial pyruvate carrier
Pyruvate dehydrogenase complex
Pyruvate dehydrogenase requires _ enzymes and _ coenzymes- name them
3 enzymes E1, E2, E3 5 coenzymes -Thyamine pyrophosphate Lipoic acid FAD NAD CoA
Pyruvate dehydrogenase is active under which phosphorylation state
Dephosphorylated is active
What are positive/negative allosteric regulators of Pyruvate dehydrogenase kinase PDK
+ Acetyl Coa, NADH, ATP
- Pyruvate, CoA, NAD+, ADP
What are positive allosteric regulators of Pyruvate dehydrogenase phosphatase PDP
Calcium and magnesium
High levels of acetyl CoA will directly inhibit which enzyme of the pyruvate dehydrogenase complex (remember 3 enzymes and 5 coenzymes)
E2
Citrate synthase
Condensation of 4-carbon oxaloacetate and 2-carbon acetyl CoA to yield Citrate
Aconitase
Citrate –> Isocitrate
Isocitrate dehydrogenase
Isocitrate-->oxalosuccinate--> a-ketoglutarate NADH + CO2 formed Rate limiting step Activated by ADP Inhibited by ATP and NADH
a-ketoglutarate dehydrogenase complex
a-ketoglutarate–> Succinyl CoA
NADH formed
Inhibited by ATP, succinyl CoA and NADH
Succinyl CoA synthetase
Succinyl CoA–> Succinate
*GTP formed- only step yielding high energy molecule
Succinate dehydrogenase
Succinate–> Fumarate
FADH2 formed
Where is succinate dehydrogenase located, and where is FADH2 sent when formed by it
Located in the inner mitochondrial membrane directly associated with electron transport chain
FADH2 passes electrons directly to Co-Q in the ETC
Fumarase
Fumarate–> Malate