Where does the citric acid cycle take place in?
mitochondrial matrix
For each acetyl group, what does the CAC produce?
2 CO2, 3 NADH, 1 FADH2, 1 GTP
What does pyruvate dehydrogenase do?
turns pyruvate into acetyl CoA
Why is Coenzyme A a high energy molecule?
thioester bond formed from the oxidation of pyruvate and the cysteamine of CoA is exergonic when hydrolyzed
What does a multienzyme complex mean?
group of non-covalently associated enzymes that catalyze two or more sequential steps in a catalytic pathway
What are benefits of multienzyme complexes?
increased reaction rate, reduced probability of competing reactions, and coordinated control
What are the three enzymes and cofactors in pyruvate DH (E1, E2, E3)?
E1: pyruvate dehydrogenase (TPP)
E2: dihydrolipoyl transacetylase (lipoamide and CoA)
E3: dihydrolipoyl dehydrogenase (FAD and NAD+)
What happens in reaction 1 of the pyruvate DH complex?
E1 decarboxylates pyruvate in a reaction that requires thiamine pyrophosphate (TPP)
What is TPP typically involved in the decarboxylation of?
alpha-keto acids
What is the important part of TPP and why?
thiazolium ring; acts as an electron sink
What happens in reaction 2 of pyruvate DH complex?
hydroxyethyl group transfer from TPP to lipoamide cofactor in E2
What happens in reaction 3 of pyruvate DH?
acetyl group transfers to CoA, catalyze a transfer esterification reaction
produce Acetyl CoA, CO2
What happens in reactions 4 and 5 of the complex?
Dihydrolipoamide is oxidized and NAD+ reduced in E3
What are the inputs and outputs of the pyruvate DH complex?
Inputs: pyruvate, CoA, NAD+
Outputs: CO2, Acetyl-CoA, NADH
Does NADH and Acetyl-CoA inhibit or activate pyruvate DH?
product inhibition, binds to active site
What is PDK and PDP?
PDK Inhibit pyruvate DH
PDPs activate pyruvate DH
What is the reactants and products in the first step in the CAC?
What is the enzyme and cofactor attached to this reaction?
oxaloacetate + acetyl-CoA to citrate
citrate synthase (CoA-SH leaves)
What are the three control points of the CAC?
1st, 3rd, and 4th steps
What is the reactants and products in the second step in the CAC?
What is the enzyme and cofactor attached to this reaction?
citrate to isocitrate
aconitase
What is the reactants and products in the third step in the CAC?
What is the enzyme and cofactor attached to this reaction?
isocitrate to alpha-ketoglutarate
isocitrate dehydrogenase, NAD+ to NADH
CO2 leaves; Mn2+
What is the purpose of Mn2+ in the third step of the CAC?
stabilizes the enolate intermediate
