TCA / Krebs Cycle Flashcards
(19 cards)
Pyruvate dehydrogenase reaction
Pyruvate + CoA + NAD+
to
Acetyl CoA + CO2 + NADH
Initial substrate for TCA cycle
Acetyl CoA
PDH’s 5 cofactors
Thiamine pyrophosphate (TPP) Lipoamide FAD/FADH2 CoA NAD+/NADH
What part of CoA is the place where chemistry takes place?
Thiol group
Acetyl CoA has a high energy bond that’s a ____ bond
Thioester bond
The ester that’s transferred to CoA to make acetyl CoA is from
Lipoamide
Pyruvate dehydrogenase reaction occurs in
Mitochondrial matrix
TCA cycle occurs in
Mitochondrial matrix
What are examples of diffusible redox cofactors
UQ
NAD+
What are examples of enzyme bound redox cofactors?
FAD
FMN
Molecular and location differences between UQ and NAD+
UQ hydrophobic and membrane bound
NAD+ polar and cytosolic
Warburg effect
Cancer cells preferentially use glycolysis over pyruvate oxidation because CA in hypoxic state before angiogenesis and glycolysis is anaerobic
Hypoxia inducible factor (HIF) inhibits PDK activity
TCA cycle overall reaction
Acetyl CoA + 3NAD+ + FAD + GDP + Pi + 2H2O
CoASH + 2 CO2 + 3 NADH + 3 H+ + FAD (2H) + GTP
TCA cycle is coupled to _______ via ________
Electron transfer chain (oxidative phosphorylation)
NADH
What ratio stimulates TCA cycle?
High NAD+/NADH ratio
High rate of oxidative phosphorylation depletes NADH levels
Which 3 enzymes have irreversible steps in TCA cycle?
Citrate synthase
Succinate dehydrogenase
α ketoglutarate dehydrogenase
Which enzyme creates the rate determining step for TCA cycle?
Isocitrate dehydrogenase
α ketoglutarate dehydrogenase is similar to
Pyruvate dehydrogenase
Energy stored in thioester bond of succinyl CoA is used for
Substrate level phosphorylation for GDP –> GTP
