Citric Acid Cycle Flashcards
Citric Acid Cycle
An 8=step process providing energy in aerobic conditions by donating electrons from NADH to FAD, which donate electrons to the ETC.
What happens in each step of CAC?
A coenzyme like NADH of FADH2 is reduced.
What do NADH and FADH2 contribute to?
The ETC thus most ATP production in humans.
Why is Acetyl CoA important in the CAC?
It is a significant carbon input
Where does acetyl-CoA derive from?
Glucose, fatty acids but mostly glucose-derived pyruvate.
What facilitates conversion of pyruvate to acetyl CoA?
Pyruvate Dehydrogenase Complex
Pyruvate Dehydrogenase Complex
An enzyme complex in CAC catalyzing oxidative decarboxylation of pyruvate to acetyl-CoA, NADH and CO2
What does PDC do generally?
Link the glycolytic pathway to CAC, regulating metabolism of pyruvate to maintain glucose homeostasis.
How does covalent modificaiton regulate PDC?
Phosphorylation of PDC first subunit pyruvate decarboxylate, reducing PDC activity.
What happens to Acetyl-CoA after synthesis from PDC?
Enters CAC
What does CAC ultimately result in?
Release of two CO2 through oxidation of acetyl group, and reducition of NADH, GTP and FADH2 in every step.
What is the first step in Citric Acid Cycl?
Citrate synthase catalyses condensation reaction of acetyl CoA and ocaloacetate, to form citrate.
What is the second step of the Citric Acid Cycle?
Citrate is isomerised by aconitase, forming isocitrate.
What is the third step of citric acid cycle?
Isocitrate is oxidatively decarboxylated by isocitrate dehydrogenase, releasing CO2 and alpha-ketoglutarate.
What is the fourth step of Citric Acid Cycle?
Alpha-ketoglutarate by the AKDC, forming succinyl-CoA, producing NADH.
What is the fifth step of the Citric Acid Cycle?
Succinyl CoA is cleaved by succinate thiokinase, forming succinate and GTP.
What is the sixth step of the Citric Acid Cycle?
Succinate is oxidised to fumarate by succinate dehydrogenase, producing reduced FADH2 from FAD
What is the seventh step of the Citric Acid Cycle?
Fumarase oxidises fumarate to form malate
What is the eight step of the Citric Acid Cycle?
Malate is oxidised by malate dehydrogenase to form oxaloacetate.
isocitrate dehydrogenase
This catalyses oxidative decarboxylation of isocitrate into CO2 and alpha-ketoglutarate.
What is the mechanism of alpha-ketoglutarate decarboxylation?
E1 decarboxylates alpha-ketoglutarate, transferring four carbons to thiamine pyrophosphate cofactor, where then E2 transfers the succinyl group to CoASH, with assistnace form FAD, then E3 synthesises FAD along with NADH from NAD+ so that the dehydrogenase complex maintains the substrates and cofactors for continued reacitons.
What citric acid cycle steps are irreversible?
citrate synthase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.
